Merge remote-tracking branch 'upstream/develop' into package-opencv

* upstream/develop: (126 commits)
  Fix indent/flake8 error.
  openexr : Add new package
  Set environment variables
  Added gnu packages datamash, parallel, and screen
  added package as argument to setup_platform_environment
  ilmbase : Add new IlmBase package
  Documented linker default
  fixed flake errors
  removed commented-out code
  Set default link type to dynamic on cray. Includes hooks for platform-based environment changes
  fixed flake errors
  fixed flake errors
  Improved cray_xc detection bug fix
  Improved cray_xc detection
  remove FIXMEs
  Ensure that per-4.4.1 NetCDF doesn't use HDF5 1.10
  Re-ignore licenses directory
  Add "default" configuration scope.
  Draft CDO
  Make frontend OS on Cray machines a proper linux distro.
  ...

49 files changed, 1729 insertions, 858 deletions

diff --git a/lib/spack/docs/basic_usage.rst b/lib/spack/docs/basic_usage.rst
index dbad0a9f6d..948092047b 100644
--- a/lib/spack/docs/basic_usage.rst
+++ b/lib/spack/docs/basic_usage.rst
@@ -183,7 +183,7 @@ To uninstall a package and every package that depends on it, you may give the
 
    spack uninstall --dependents mpich
 
-will display a list of all the packages that depends on `mpich` and, upon confirmation,
+will display a list of all the packages that depend on `mpich` and, upon confirmation,
 will uninstall them in the right order.
 
 A line like
@@ -543,11 +543,12 @@ More formally, a spec consists of the following pieces:
 * ``+`` or ``-`` or ``~`` Optional variant specifiers (``+debug``,
   ``-qt``, or ``~qt``) for boolean variants
 * ``name=<value>`` Optional variant specifiers that are not restricted to
-boolean variants
+  boolean variants
 * ``name=<value>`` Optional compiler flag specifiers. Valid flag names are
-``cflags``, ``cxxflags``, ``fflags``, ``cppflags``, ``ldflags``, and ``ldlibs``.
+  ``cflags``, ``cxxflags``, ``fflags``, ``cppflags``, ``ldflags``, and ``ldlibs``.
 * ``target=<value> os=<value>`` Optional architecture specifier 
-(``target=haswell os=CNL10``) * ``^`` Dependency specs (``^callpath@1.1``)
+  (``target=haswell os=CNL10``)
+* ``^`` Dependency specs (``^callpath@1.1``)
 
 There are two things to notice here.  The first is that specs are
 recursively defined.  That is, each dependency after ``^`` is a spec
@@ -1865,6 +1866,10 @@ to call the Cray compiler wrappers during build time.
 
 For more on compiler configuration, check out :ref:`compiler-config`.
 
+Spack sets the default Cray link type to dynamic, to better match other
+other platforms. Individual packages can enable static linking (which is the
+default outside of Spack on cray systems) using the -static flag.
+
 Setting defaults and using Cray modules
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/lib/spack/docs/packaging_guide.rst b/lib/spack/docs/packaging_guide.rst
index 0f549e2957..70def5c39a 100644
--- a/lib/spack/docs/packaging_guide.rst
+++ b/lib/spack/docs/packaging_guide.rst
@@ -1286,6 +1286,31 @@ command line to find installed packages or to install packages with
 particular constraints, and package authors can use specs to describe
 relationships between packages.
 
+Additionally, dependencies may be specified for specific use cases:
+
+.. code-block:: python
+
+    depends_on("cmake", type="build")
+    depends_on("libelf", type=("build", "link"))
+    depends_on("python", type="run")
+
+The dependency types are:
+
+  * **"build"**: made available during the project's build. The package will
+    be added to ``PATH``, the compiler include paths, and ``PYTHONPATH``.
+    Other projects which depend on this one will not have these modified
+    (building project X doesn't need project Y's build dependencies).
+  * **"link"**: the project is linked to by the project. The package will be
+    added to the current package's ``rpath``.
+  * **"run"**: the project is used by the project at runtime. The package will
+    be added to ``PATH`` and ``PYTHONPATH``.
+
+If not specified, ``type`` is assumed to be ``("build", "link")``. This is the
+common case for compiled language usage. Also available are the aliases
+``"alldeps"`` for all dependency types and ``"nolink"`` (``("build", "run")``)
+for use by dependencies which are not expressed via a linker (e.g., Python or
+Lua module loading).
+
 .. _setup-dependent-environment:
 
 ``setup_dependent_environment()``
@@ -2602,14 +2627,14 @@ Spack packages with variants similar to already-existing Spack
 packages should use the same name for their variants.  Standard
 variant names are:
 
-======= ======== ========================
-Name    Default   Description
-------- -------- ------------------------
-shared   True     Build shared libraries
-static            Build static libraries
-mpi               Use MPI
-python            Build Python extension
-------- -------- ------------------------
+  ======= ======== ========================
+  Name    Default   Description
+  ======= ======== ========================
+  shared   True     Build shared libraries
+  static            Build static libraries
+  mpi               Use MPI
+  python            Build Python extension
+  ======= ======== ========================
 
 If specified in this table, the corresponding default should be used
 when declaring a variant.
diff --git a/lib/spack/env/cc b/lib/spack/env/cc
index bf98b4c354..c6bb50d261 100755
--- a/lib/spack/env/cc
+++ b/lib/spack/env/cc
@@ -110,13 +110,13 @@ case "$command" in
         comp="CXX"
         lang_flags=CXX
         ;;
-    f90|fc|f95|gfortran|ifort|pgfortran|xlf90|nagfor)
+    ftn|f90|fc|f95|gfortran|ifort|pgfortran|xlf90|nagfor)
         command="$SPACK_FC"
         language="Fortran 90"
         comp="FC"
         lang_flags=F
         ;;
-    f77|gfortran|ifort|pgfortran|xlf|nagfor)
+    f77|gfortran|ifort|pgfortran|xlf|nagfor|ftn)
         command="$SPACK_F77"
         language="Fortran 77"
         comp="F77"
diff --git a/lib/spack/env/craype/CC b/lib/spack/env/craype/CC
new file mode 120000
index 0000000000..82c2b8e90a
--- /dev/null
+++ b/lib/spack/env/craype/CC
@@ -0,0 +1 @@
+../cc
\ No newline at end of file
diff --git a/lib/spack/env/craype/cc b/lib/spack/env/craype/cc
new file mode 120000
index 0000000000..82c2b8e90a
--- /dev/null
+++ b/lib/spack/env/craype/cc
@@ -0,0 +1 @@
+../cc
\ No newline at end of file
diff --git a/lib/spack/env/craype/ftn b/lib/spack/env/craype/ftn
new file mode 120000
index 0000000000..82c2b8e90a
--- /dev/null
+++ b/lib/spack/env/craype/ftn
@@ -0,0 +1 @@
+../cc
\ No newline at end of file
diff --git a/lib/spack/llnl/util/filesystem.py b/lib/spack/llnl/util/filesystem.py
index e800c6717a..6e4cd338fe 100644
--- a/lib/spack/llnl/util/filesystem.py
+++ b/lib/spack/llnl/util/filesystem.py
@@ -42,7 +42,7 @@ __all__ = ['set_install_permissions', 'install', 'install_tree',
            'FileFilter', 'change_sed_delimiter', 'is_exe', 'force_symlink',
            'set_executable', 'copy_mode', 'unset_executable_mode',
            'remove_dead_links', 'remove_linked_tree', 'find_library_path',
-           'fix_darwin_install_name', 'to_link_flags']
+           'fix_darwin_install_name', 'to_link_flags', 'to_lib_name']
 
 
 def filter_file(regex, repl, *filenames, **kwargs):
@@ -431,6 +431,13 @@ def fix_darwin_install_name(path):
                     break
 
 
+def to_lib_name(library):
+    """Transforms a path to the library /path/to/lib<name>.xyz into <name>
+    """
+    # Assume libXYZ.suffix
+    return os.path.basename(library)[3:].split(".")[0]
+
+
 def to_link_flags(library):
     """Transforms a path to a <library> into linking flags -L<dir> -l<name>.
 
@@ -438,8 +445,7 @@ def to_link_flags(library):
       A string of linking flags.
     """
     dir  = os.path.dirname(library)
-    # Assume libXYZ.suffix
-    name = os.path.basename(library)[3:].split(".")[0]
+    name = to_lib_name(library)
     res = '-L%s -l%s' % (dir, name)
     return res
 
diff --git a/lib/spack/spack/__init__.py b/lib/spack/spack/__init__.py
index 20c9934704..d67585aac4 100644
--- a/lib/spack/spack/__init__.py
+++ b/lib/spack/spack/__init__.py
@@ -177,10 +177,11 @@ sys_type = None
 #       should live.  This file is overloaded for spack core vs. for packages.
 #
 __all__ = ['Package', 'StagedPackage', 'CMakePackage', \
-    'Version', 'when', 'ver']
+    'Version', 'when', 'ver', 'alldeps', 'nolink']
 from spack.package import Package, ExtensionConflictError
 from spack.package import StagedPackage, CMakePackage
 from spack.version import Version, ver
+from spack.spec import DependencySpec, alldeps, nolink
 from spack.multimethod import when
 
 import llnl.util.filesystem
diff --git a/lib/spack/spack/architecture.py b/lib/spack/spack/architecture.py
index a7cda2bf68..974505ee3a 100644
--- a/lib/spack/spack/architecture.py
+++ b/lib/spack/spack/architecture.py
@@ -76,7 +76,6 @@ attributes front_os and back_os. The operating system as described earlier,
 will be responsible for compiler detection.
 """
 import os
-import imp
 import inspect
 
 from llnl.util.lang import memoized, list_modules, key_ordering
@@ -190,6 +189,12 @@ class Platform(object):
 
         return self.operating_sys.get(name, None)
 
+    @classmethod
+    def setup_platform_environment(self, pkg, env):
+        """ Subclass can override this method if it requires any
+            platform-specific build environment modifications.
+        """
+        pass
 
     @classmethod
     def detect(self):
@@ -200,15 +205,12 @@ class Platform(object):
         """
         raise NotImplementedError()
 
-
     def __repr__(self):
         return self.__str__()
 
-
     def __str__(self):
         return self.name
 
-
     def _cmp_key(self):
         t_keys = ''.join(str(t._cmp_key()) for t in
                          sorted(self.targets.values()))
@@ -279,7 +281,7 @@ class OperatingSystem(object):
 
         # ensure all the version calls we made are cached in the parent
         # process, as well.  This speeds up Spack a lot.
-        clist = reduce(lambda x, y: x+y, compiler_lists)
+        clist = reduce(lambda x, y: x + y, compiler_lists)
         return clist
 
     def find_compiler(self, cmp_cls, *path):
@@ -320,7 +322,7 @@ class OperatingSystem(object):
 
                 # prefer the one with more compilers.
                 prev_paths = [prev.cc, prev.cxx, prev.f77, prev.fc]
-                newcount = len([p for p in paths       if p is not None])
+                newcount = len([p for p in paths if p is not None])
                 prevcount = len([p for p in prev_paths if p is not None])
 
                 # Don't add if it's not an improvement over prev compiler.
@@ -337,6 +339,7 @@ class OperatingSystem(object):
         d['version'] = self.version
         return d
 
+
 @key_ordering
 class Arch(object):
     """Architecture is now a class to help with setting attributes.
@@ -377,11 +380,9 @@ class Arch(object):
         else:
             return ''
 
-
     def __contains__(self, string):
         return string in str(self)
 
-
     def _cmp_key(self):
         if isinstance(self.platform, Platform):
             platform = self.platform.name
@@ -424,7 +425,7 @@ def _operating_system_from_dict(os_name, plat=None):
     if isinstance(os_name, dict):
         name = os_name['name']
         version = os_name['version']
-        return plat.operating_system(name+version)
+        return plat.operating_system(name + version)
     else:
         return plat.operating_system(os_name)
 
diff --git a/lib/spack/spack/build_environment.py b/lib/spack/spack/build_environment.py
index fe5186a7d7..5affd3c7c5 100644
--- a/lib/spack/spack/build_environment.py
+++ b/lib/spack/spack/build_environment.py
@@ -254,7 +254,8 @@ def set_build_environment_variables(pkg, env, dirty=False):
     env.set_path(SPACK_ENV_PATH, env_paths)
 
     # Prefixes of all of the package's dependencies go in SPACK_DEPENDENCIES
-    dep_prefixes = [d.prefix for d in pkg.spec.traverse(root=False)]
+    dep_prefixes = [d.prefix
+                    for d in pkg.spec.traverse(root=False, deptype='build')]
     env.set_path(SPACK_DEPENDENCIES, dep_prefixes)
     # Add dependencies to CMAKE_PREFIX_PATH
     env.set_path('CMAKE_PREFIX_PATH', dep_prefixes)
@@ -337,10 +338,6 @@ def set_module_variables_for_package(pkg, module):
     # Don't use which for this; we want to find it in the current dir.
     m.configure = Executable('./configure')
 
-    # TODO: shouldn't really use "which" here.  Consider adding notion
-    # TODO: of build dependencies, as opposed to link dependencies.
-    # TODO: Currently, everything is a link dependency, but tools like
-    # TODO: this shouldn't be.
     m.cmake = Executable('cmake')
     m.ctest = Executable('ctest')
 
@@ -388,9 +385,10 @@ def set_module_variables_for_package(pkg, module):
 def get_rpaths(pkg):
     """Get a list of all the rpaths for a package."""
     rpaths = [pkg.prefix.lib, pkg.prefix.lib64]
-    rpaths.extend(d.prefix.lib for d in pkg.spec.dependencies.values()
+    deps = pkg.spec.dependencies(deptype='link')
+    rpaths.extend(d.prefix.lib for d in deps
                   if os.path.isdir(d.prefix.lib))
-    rpaths.extend(d.prefix.lib64 for d in pkg.spec.dependencies.values()
+    rpaths.extend(d.prefix.lib64 for d in deps
                   if os.path.isdir(d.prefix.lib64))
     # Second module is our compiler mod name. We use that to get rpaths from
     # module show output.
@@ -446,10 +444,11 @@ def setup_package(pkg, dirty=False):
 
     set_compiler_environment_variables(pkg, spack_env)
     set_build_environment_variables(pkg, spack_env, dirty)
+    pkg.spec.architecture.platform.setup_platform_environment(pkg, spack_env)
     load_external_modules(pkg)
     # traverse in postorder so package can use vars from its dependencies
     spec = pkg.spec
-    for dspec in pkg.spec.traverse(order='post', root=False):
+    for dspec in pkg.spec.traverse(order='post', root=False, deptype='build'):
         # If a user makes their own package repo, e.g.
         # spack.repos.mystuff.libelf.Libelf, and they inherit from
         # an existing class like spack.repos.original.libelf.Libelf,
diff --git a/lib/spack/spack/cmd/__init__.py b/lib/spack/spack/cmd/__init__.py
index 672999159c..230115df50 100644
--- a/lib/spack/spack/cmd/__init__.py
+++ b/lib/spack/spack/cmd/__init__.py
@@ -27,16 +27,18 @@ import re
 import sys
 
 import llnl.util.tty as tty
-from llnl.util.lang import attr_setdefault
-
 import spack
-import spack.spec
 import spack.config
+import spack.spec
+from llnl.util.lang import *
+from llnl.util.tty.colify import *
+from llnl.util.tty.color import *
 
 #
 # Settings for commands that modify configuration
 #
-# Commands that modify confguration By default modify the *highest* priority scope.
+# Commands that modify confguration By default modify the *highest*
+# priority scope.
 default_modify_scope = spack.config.highest_precedence_scope().name
 # Commands that list confguration list *all* scopes by default.
 default_list_scope = None
@@ -48,7 +50,7 @@ python_list = list
 ignore_files = r'^\.|^__init__.py$|^#'
 
 SETUP_PARSER = "setup_parser"
-DESCRIPTION  = "description"
+DESCRIPTION = "description"
 
 command_path = os.path.join(spack.lib_path, "spack", "cmd")
 
@@ -71,7 +73,7 @@ def get_module(name):
         module_name, fromlist=[name, SETUP_PARSER, DESCRIPTION],
         level=0)
 
-    attr_setdefault(module, SETUP_PARSER, lambda *args: None) # null-op
+    attr_setdefault(module, SETUP_PARSER, lambda *args: None)  # null-op
     attr_setdefault(module, DESCRIPTION, "")
 
     fn_name = get_cmd_function_name(name)
@@ -101,17 +103,17 @@ def parse_specs(args, **kwargs):
         specs = spack.spec.parse(args)
         for spec in specs:
             if concretize:
-                spec.concretize() # implies normalize
+                spec.concretize()  # implies normalize
             elif normalize:
                 spec.normalize()
 
         return specs
 
-    except spack.parse.ParseError, e:
+    except spack.parse.ParseError as e:
         tty.error(e.message, e.string, e.pos * " " + "^")
         sys.exit(1)
 
-    except spack.spec.SpecError, e:
+    except spack.spec.SpecError as e:
         tty.error(e.message)
         sys.exit(1)
 
@@ -127,7 +129,7 @@ def elide_list(line_list, max_num=10):
            [1, 2, 3, '...', 6]
     """
     if len(line_list) > max_num:
-        return line_list[:max_num-1] + ['...'] + line_list[-1:]
+        return line_list[:max_num - 1] + ['...'] + line_list[-1:]
     else:
         return line_list
 
@@ -138,10 +140,104 @@ def disambiguate_spec(spec):
         tty.die("Spec '%s' matches no installed packages." % spec)
 
     elif len(matching_specs) > 1:
-        args =  ["%s matches multiple packages." % spec,
-                 "Matching packages:"]
+        args = ["%s matches multiple packages." % spec,
+                "Matching packages:"]
         args += ["  " + str(s) for s in matching_specs]
         args += ["Use a more specific spec."]
         tty.die(*args)
 
     return matching_specs[0]
+
+
+def ask_for_confirmation(message):
+    while True:
+        tty.msg(message + '[y/n]')
+        choice = raw_input().lower()
+        if choice == 'y':
+            break
+        elif choice == 'n':
+            raise SystemExit('Operation aborted')
+        tty.warn('Please reply either "y" or "n"')
+
+
+def gray_hash(spec, length):
+    return colorize('@K{%s}' % spec.dag_hash(length))
+
+
+def display_specs(specs, **kwargs):
+    mode = kwargs.get('mode', 'short')
+    hashes = kwargs.get('long', False)
+    namespace = kwargs.get('namespace', False)
+    flags = kwargs.get('show_flags', False)
+    variants = kwargs.get('variants', False)
+
+    hlen = 7
+    if kwargs.get('very_long', False):
+        hashes = True
+        hlen = None
+
+    nfmt = '.' if namespace else '_'
+    ffmt = '$%+' if flags else ''
+    vfmt = '$+' if variants else ''
+    format_string = '$%s$@%s%s' % (nfmt, ffmt, vfmt)
+
+    # Make a dict with specs keyed by architecture and compiler.
+    index = index_by(specs, ('architecture', 'compiler'))
+
+    # Traverse the index and print out each package
+    for i, (architecture, compiler) in enumerate(sorted(index)):
+        if i > 0:
+            print
+
+        header = "%s{%s} / %s{%s}" % (spack.spec.architecture_color,
+                                      architecture, spack.spec.compiler_color,
+                                      compiler)
+        tty.hline(colorize(header), char='-')
+
+        specs = index[(architecture, compiler)]
+        specs.sort()
+
+        abbreviated = [s.format(format_string, color=True) for s in specs]
+        if mode == 'paths':
+            # Print one spec per line along with prefix path
+            width = max(len(s) for s in abbreviated)
+            width += 2
+            format = "    %%-%ds%%s" % width
+
+            for abbrv, spec in zip(abbreviated, specs):
+                if hashes:
+                    print(gray_hash(spec, hlen), )
+                print(format % (abbrv, spec.prefix))
+
+        elif mode == 'deps':
+            for spec in specs:
+                print(spec.tree(
+                    format=format_string,
+                    color=True,
+                    indent=4,
+                    prefix=(lambda s: gray_hash(s, hlen)) if hashes else None))
+
+        elif mode == 'short':
+            # Print columns of output if not printing flags
+            if not flags:
+
+                def fmt(s):
+                    string = ""
+                    if hashes:
+                        string += gray_hash(s, hlen) + ' '
+                    string += s.format('$-%s$@%s' % (nfmt, vfmt), color=True)
+
+                    return string
+
+                colify(fmt(s) for s in specs)
+            # Print one entry per line if including flags
+            else:
+                for spec in specs:
+                    # Print the hash if necessary
+                    hsh = gray_hash(spec, hlen) + ' ' if hashes else ''
+                    print(hsh + spec.format(format_string, color=True) + '\n')
+
+        else:
+            raise ValueError(
+                "Invalid mode for display_specs: %s. Must be one of (paths,"
+                "deps, short)." % mode)  # NOQA: ignore=E501
diff --git a/lib/spack/spack/cmd/bootstrap.py b/lib/spack/spack/cmd/bootstrap.py
index bec11439b5..60e2bd3a11 100644
--- a/lib/spack/spack/cmd/bootstrap.py
+++ b/lib/spack/spack/cmd/bootstrap.py
@@ -23,7 +23,6 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
 import os
-from subprocess import check_call
 
 import llnl.util.tty as tty
 from llnl.util.filesystem import join_path, mkdirp
@@ -31,26 +30,49 @@ from llnl.util.filesystem import join_path, mkdirp
 import spack
 from spack.util.executable import which
 
+_SPACK_UPSTREAM = 'https://github.com/llnl/spack'
+
 description = "Create a new installation of spack in another prefix"
 
+
 def setup_parser(subparser):
-    subparser.add_argument('prefix', help="names of prefix where we should install spack")
+    subparser.add_argument(
+        '-r', '--remote', action='store', dest='remote',
+        help="name of the remote to bootstrap from", default='origin')
+    subparser.add_argument(
+        'prefix',
+        help="names of prefix where we should install spack")
 
 
-def get_origin_url():
+def get_origin_info(remote):
     git_dir = join_path(spack.prefix, '.git')
     git = which('git', required=True)
-    origin_url = git(
-        '--git-dir=%s' % git_dir, 'config', '--get', 'remote.origin.url',
-        output=str)
-    return origin_url.strip()
+    try:
+        branch = git('symbolic-ref', '--short', 'HEAD', output=str)
+    except ProcessError:
+        branch = 'develop'
+        tty.warn('No branch found; using default branch: %s' % branch)
+    if remote == 'origin' and \
+       branch not in ('master', 'develop'):
+        branch = 'develop'
+        tty.warn('Unknown branch found; using default branch: %s' % branch)
+    try:
+        origin_url = git(
+            '--git-dir=%s' % git_dir,
+            'config', '--get', 'remote.%s.url' % remote,
+            output=str)
+    except ProcessError:
+        origin_url = _SPACK_UPSTREAM
+        tty.warn('No git repository found; '
+                 'using default upstream URL: %s' % origin_url)
+    return (origin_url.strip(), branch.strip())
 
 
 def bootstrap(parser, args):
-    origin_url = get_origin_url()
+    origin_url, branch = get_origin_info(args.remote)
     prefix = args.prefix
 
-    tty.msg("Fetching spack from origin: %s" % origin_url)
+    tty.msg("Fetching spack from '%s': %s" % (args.remote, origin_url))
 
     if os.path.isfile(prefix):
         tty.die("There is already a file at %s" % prefix)
@@ -62,7 +84,8 @@ def bootstrap(parser, args):
 
     files_in_the_way = os.listdir(prefix)
     if files_in_the_way:
-        tty.die("There are already files there!  Delete these files before boostrapping spack.",
+        tty.die("There are already files there! "
+                "Delete these files before boostrapping spack.",
                 *files_in_the_way)
 
     tty.msg("Installing:",
@@ -73,8 +96,10 @@ def bootstrap(parser, args):
     git = which('git', required=True)
     git('init', '--shared', '-q')
     git('remote', 'add', 'origin', origin_url)
-    git('fetch', 'origin', 'master:refs/remotes/origin/master', '-n', '-q')
-    git('reset', '--hard', 'origin/master', '-q')
+    git('fetch', 'origin', '%s:refs/remotes/origin/%s' % (branch, branch),
+                           '-n', '-q')
+    git('reset', '--hard', 'origin/%s' % branch, '-q')
+    git('checkout', '-B', branch, 'origin/%s' % branch, '-q')
 
     tty.msg("Successfully created a new spack in %s" % prefix,
             "Run %s/bin/spack to use this installation." % prefix)
diff --git a/lib/spack/spack/cmd/checksum.py b/lib/spack/spack/cmd/checksum.py
index 95bd4771ed..aedb0fd99c 100644
--- a/lib/spack/spack/cmd/checksum.py
+++ b/lib/spack/spack/cmd/checksum.py
@@ -42,7 +42,8 @@ def setup_parser(subparser):
         '--keep-stage', action='store_true', dest='keep_stage',
         help="Don't clean up staging area when command completes.")
     subparser.add_argument(
-        'versions', nargs=argparse.REMAINDER, help='Versions to generate checksums for')
+        'versions', nargs=argparse.REMAINDER,
+        help='Versions to generate checksums for')
 
 
 def get_checksums(versions, urls, **kwargs):
@@ -59,10 +60,10 @@ def get_checksums(versions, urls, **kwargs):
             with Stage(url, keep=keep_stage) as stage:
                 stage.fetch()
                 if i == 0 and first_stage_function:
-                    first_stage_function(stage)
+                    first_stage_function(stage, url)
 
-                hashes.append((version,
-                               spack.util.crypto.checksum(hashlib.md5, stage.archive_file)))
+                hashes.append((version, spack.util.crypto.checksum(
+                    hashlib.md5, stage.archive_file)))
                 i += 1
         except FailedDownloadError as e:
             tty.msg("Failed to fetch %s" % url)
@@ -79,12 +80,12 @@ def checksum(parser, args):
     # If the user asked for specific versions, use those.
     if args.versions:
         versions = {}
-        for v in args.versions:
-            v = ver(v)
-            if not isinstance(v, Version):
+        for version in args.versions:
+            version = ver(version)
+            if not isinstance(version, Version):
                 tty.die("Cannot generate checksums for version lists or " +
                         "version ranges.  Use unambiguous versions.")
-            versions[v] = pkg.url_for_version(v)
+            versions[version] = pkg.url_for_version(version)
     else:
         versions = pkg.fetch_remote_versions()
         if not versions:
@@ -111,5 +112,7 @@ def checksum(parser, args):
     if not version_hashes:
         tty.die("Could not fetch any versions for %s" % pkg.name)
 
-    version_lines = ["    version('%s', '%s')" % (v, h) for v, h in version_hashes]
+    version_lines = [
+        "    version('%s', '%s')" % (v, h) for v, h in version_hashes
+    ]
     tty.msg("Checksummed new versions of %s:" % pkg.name, *version_lines)
diff --git a/lib/spack/spack/cmd/common/__init__.py b/lib/spack/spack/cmd/common/__init__.py
new file mode 100644
index 0000000000..ed1ec23bca
--- /dev/null
+++ b/lib/spack/spack/cmd/common/__init__.py
@@ -0,0 +1,24 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
diff --git a/lib/spack/spack/cmd/common/arguments.py b/lib/spack/spack/cmd/common/arguments.py
new file mode 100644
index 0000000000..af04170824
--- /dev/null
+++ b/lib/spack/spack/cmd/common/arguments.py
@@ -0,0 +1,96 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+
+import argparse
+
+import spack.modules
+from spack.util.pattern import Bunch
+__all__ = ['add_common_arguments']
+
+_arguments = {}
+
+
+def add_common_arguments(parser, list_of_arguments):
+    for argument in list_of_arguments:
+        if argument not in _arguments:
+            message = 'Trying to add the non existing argument "{0}" to a command'  # NOQA: ignore=E501
+            raise KeyError(message.format(argument))
+        x = _arguments[argument]
+        parser.add_argument(*x.flags, **x.kwargs)
+
+
+class ConstraintAction(argparse.Action):
+    """Constructs a list of specs based on a constraint given on the command line
+
+    An instance of this class is supposed to be used as an argument action
+    in a parser. It will read a constraint and will attach a list of matching
+    specs to the namespace
+    """
+    qualifiers = {}
+
+    def __call__(self, parser, namespace, values, option_string=None):
+        # Query specs from command line
+        d = self.qualifiers.get(namespace.subparser_name, {})
+        specs = [s for s in spack.installed_db.query(**d)]
+        values = ' '.join(values)
+        if values:
+            specs = [x for x in specs if x.satisfies(values, strict=True)]
+        namespace.specs = specs
+
+parms = Bunch(
+    flags=('constraint',),
+    kwargs={
+        'nargs': '*',
+        'help': 'Constraint to select a subset of installed packages',
+        'action': ConstraintAction
+    })
+_arguments['constraint'] = parms
+
+parms = Bunch(
+    flags=('-m', '--module-type'),
+    kwargs={
+        'help': 'Type of module files',
+        'default': 'tcl',
+        'choices': spack.modules.module_types
+    })
+_arguments['module_type'] = parms
+
+parms = Bunch(
+    flags=('-y', '--yes-to-all'),
+    kwargs={
+        'action': 'store_true',
+        'dest': 'yes_to_all',
+        'help': 'Assume "yes" is the answer to every confirmation asked to the user.'  # NOQA: ignore=E501
+    })
+_arguments['yes_to_all'] = parms
+
+parms = Bunch(
+    flags=('-r', '--dependencies'),
+    kwargs={
+        'action': 'store_true',
+        'dest': 'recurse_dependencies',
+        'help': 'Recursively traverse spec dependencies'
+    })
+_arguments['recurse_dependencies'] = parms
diff --git a/lib/spack/spack/cmd/create.py b/lib/spack/spack/cmd/create.py
index 18c748e483..2c440096d1 100644
--- a/lib/spack/spack/cmd/create.py
+++ b/lib/spack/spack/cmd/create.py
@@ -103,6 +103,64 @@ ${versions}
 ${install}
 """)
 
+# Build dependencies and extensions
+dependencies_dict = {
+    'autotools': "# depends_on('foo')",
+    'cmake':     "depends_on('cmake')",
+    'scons':     "depends_on('scons')",
+    'python':    "extends('python')",
+    'R':         "extends('R')",
+    'octave':    "extends('octave')",
+    'unknown':   "# depends_on('foo')"
+}
+
+# Default installation instructions
+install_dict = {
+    'autotools': """\
+        # FIXME: Modify the configure line to suit your build system here.
+        configure('--prefix={0}'.format(prefix))
+
+        # FIXME: Add logic to build and install here.
+        make()
+        make('install')""",
+
+    'cmake': """\
+        with working_dir('spack-build', create=True):
+            # FIXME: Modify the cmake line to suit your build system here.
+            cmake('..', *std_cmake_args)
+
+            # FIXME: Add logic to build and install here.
+            make()
+            make('install')""",
+
+    'scons': """\
+        # FIXME: Add logic to build and install here.
+        scons('prefix={0}'.format(prefix))
+        scons('install')""",
+
+    'python': """\
+        # FIXME: Add logic to build and install here.
+        python('setup.py', 'install', '--prefix={0}'.format(prefix))""",
+
+    'R': """\
+        # FIXME: Add logic to build and install here.
+        R('CMD', 'INSTALL', '--library={0}'.format(self.module.r_lib_dir),
+          self.stage.source_path)""",
+
+    'octave': """\
+        # FIXME: Add logic to build and install here.
+        octave('--quiet', '--norc',
+               '--built-in-docstrings-file=/dev/null',
+               '--texi-macros-file=/dev/null',
+               '--eval', 'pkg prefix {0}; pkg install {1}'.format(
+                   prefix, self.stage.archive_file))""",
+
+    'unknown': """\
+        # FIXME: Unknown build system
+        make()
+        make('install')"""
+}
+
 
 def make_version_calls(ver_hash_tuples):
     """Adds a version() call to the package for each version found."""
@@ -133,60 +191,17 @@ def setup_parser(subparser):
     setup_parser.subparser = subparser
 
 
-class ConfigureGuesser(object):
-    def __call__(self, stage):
-        """Try to guess the type of build system used by the project.
-        Set any necessary build dependencies or extensions.
-        Set the appropriate default installation instructions."""
-
-        # Build dependencies and extensions
-        dependenciesDict = {
-            'autotools': "# depends_on('foo')",
-            'cmake':     "depends_on('cmake')",
-            'scons':     "depends_on('scons')",
-            'python':    "extends('python')",
-            'R':         "extends('R')",
-            'unknown':   "# depends_on('foo')"
-        }
-
-        # Default installation instructions
-        installDict = {
-            'autotools': """\
-        # FIXME: Modify the configure line to suit your build system here.
-        configure('--prefix={0}'.format(prefix))
-
-        # FIXME: Add logic to build and install here.
-        make()
-        make('install')""",
-
-            'cmake':     """\
-        with working_dir('spack-build', create=True):
-            # FIXME: Modify the cmake line to suit your build system here.
-            cmake('..', *std_cmake_args)
+class BuildSystemGuesser(object):
+    def __call__(self, stage, url):
+        """Try to guess the type of build system used by a project based on
+        the contents of its archive or the URL it was downloaded from."""
 
-            # FIXME: Add logic to build and install here.
-            make()
-            make('install')""",
-
-            'scons':     """\
-        # FIXME: Add logic to build and install here.
-        scons('prefix={0}'.format(prefix))
-        scons('install')""",
-
-            'python':    """\
-        # FIXME: Add logic to build and install here.
-        python('setup.py', 'install', '--prefix={0}'.format(prefix))""",
-
-            'R':         """\
-        # FIXME: Add logic to build and install here.
-        R('CMD', 'INSTALL', '--library={0}'.format(self.module.r_lib_dir),
-          self.stage.source_path)""",
-
-            'unknown':   """\
-        # FIXME: Unknown build system
-        make()
-        make('install')"""
-        }
+        # Most octave extensions are hosted on Octave-Forge:
+        #     http://octave.sourceforge.net/index.html
+        # They all have the same base URL.
+        if 'downloads.sourceforge.net/octave/' in url:
+            self.build_system = 'octave'
+            return
 
         # A list of clues that give us an idea of the build system a package
         # uses. If the regular expression matches a file contained in the
@@ -224,12 +239,6 @@ class ConfigureGuesser(object):
 
         self.build_system = build_system
 
-        # Set any necessary build dependencies or extensions.
-        self.dependencies = dependenciesDict[build_system]
-
-        # Set the appropriate default installation instructions
-        self.install = installDict[build_system]
-
 
 def guess_name_and_version(url, args):
     # Try to deduce name and version of the new package from the URL
@@ -334,8 +343,8 @@ def create(parser, args):
     # Fetch tarballs (prompting user if necessary)
     versions, urls = fetch_tarballs(url, name, version)
 
-    # Try to guess what configure system is used.
-    guesser = ConfigureGuesser()
+    # Try to guess what build system is used.
+    guesser = BuildSystemGuesser()
     ver_hash_tuples = spack.cmd.checksum.get_checksums(
         versions, urls,
         first_stage_function=guesser,
@@ -344,13 +353,13 @@ def create(parser, args):
     if not ver_hash_tuples:
         tty.die("Could not fetch any tarballs for %s" % name)
 
-    # Prepend 'py-' to python package names, by convention.
+    # Add prefix to package name if it is an extension.
     if guesser.build_system == 'python':
-        name = 'py-%s' % name
-
-    # Prepend 'r-' to R package names, by convention.
+        name = 'py-{0}'.format(name)
     if guesser.build_system == 'R':
-        name = 'r-%s' % name
+        name = 'r-{0}'.format(name)
+    if guesser.build_system == 'octave':
+        name = 'octave-{0}'.format(name)
 
     # Create a directory for the new package.
     pkg_path = repo.filename_for_package_name(name)
@@ -367,8 +376,8 @@ def create(parser, args):
                 class_name=mod_to_class(name),
                 url=url,
                 versions=make_version_calls(ver_hash_tuples),
-                dependencies=guesser.dependencies,
-                install=guesser.install))
+                dependencies=dependencies_dict[guesser.build_system],
+                install=install_dict[guesser.build_system]))
 
     # If everything checks out, go ahead and edit.
     spack.editor(pkg_path)
diff --git a/lib/spack/spack/cmd/fetch.py b/lib/spack/spack/cmd/fetch.py
index e40caaa234..1afc51d9fa 100644
--- a/lib/spack/spack/cmd/fetch.py
+++ b/lib/spack/spack/cmd/fetch.py
@@ -51,7 +51,7 @@ def fetch(parser, args):
     for spec in specs:
         if args.missing or args.dependencies:
             to_fetch = set()
-            for s in spec.traverse():
+            for s in spec.traverse(deptype_query=spack.alldeps):
                 package = spack.repo.get(s)
                 if args.missing and package.installed:
                     continue
diff --git a/lib/spack/spack/cmd/find.py b/lib/spack/spack/cmd/find.py
index 3ec671f93f..d3ea38c573 100644
--- a/lib/spack/spack/cmd/find.py
+++ b/lib/spack/spack/cmd/find.py
@@ -31,7 +31,7 @@ import spack.spec
 from llnl.util.lang import *
 from llnl.util.tty.colify import *
 from llnl.util.tty.color import *
-from llnl.util.lang import *
+from spack.cmd import display_specs
 
 description = "Find installed spack packages"
 
@@ -104,89 +104,6 @@ def setup_parser(subparser):
                            help='optional specs to filter results')
 
 
-def gray_hash(spec, length):
-    return colorize('@K{%s}' % spec.dag_hash(length))
-
-
-def display_specs(specs, **kwargs):
-    mode = kwargs.get('mode', 'short')
-    hashes = kwargs.get('long', False)
-    namespace = kwargs.get('namespace', False)
-    flags = kwargs.get('show_flags', False)
-    variants = kwargs.get('variants', False)
-
-    hlen = 7
-    if kwargs.get('very_long', False):
-        hashes = True
-        hlen = None
-
-    nfmt = '.' if namespace else '_'
-    ffmt = '$%+' if flags else ''
-    vfmt = '$+' if variants else ''
-    format_string = '$%s$@%s%s' % (nfmt, ffmt, vfmt)
-
-    # Make a dict with specs keyed by architecture and compiler.
-    index = index_by(specs, ('architecture', 'compiler'))
-
-    # Traverse the index and print out each package
-    for i, (architecture, compiler) in enumerate(sorted(index)):
-        if i > 0:
-            print
-
-        header = "%s{%s} / %s{%s}" % (spack.spec.architecture_color,
-                                      architecture, spack.spec.compiler_color,
-                                      compiler)
-        tty.hline(colorize(header), char='-')
-
-        specs = index[(architecture, compiler)]
-        specs.sort()
-
-        abbreviated = [s.format(format_string, color=True) for s in specs]
-        if mode == 'paths':
-            # Print one spec per line along with prefix path
-            width = max(len(s) for s in abbreviated)
-            width += 2
-            format = "    %%-%ds%%s" % width
-
-            for abbrv, spec in zip(abbreviated, specs):
-                if hashes:
-                    print(gray_hash(spec, hlen), )
-                print(format % (abbrv, spec.prefix))
-
-        elif mode == 'deps':
-            for spec in specs:
-                print(spec.tree(
-                    format=format_string,
-                    color=True,
-                    indent=4,
-                    prefix=(lambda s: gray_hash(s, hlen)) if hashes else None))
-
-        elif mode == 'short':
-            # Print columns of output if not printing flags
-            if not flags:
-
-                def fmt(s):
-                    string = ""
-                    if hashes:
-                        string += gray_hash(s, hlen) + ' '
-                    string += s.format('$-%s$@%s' % (nfmt, vfmt), color=True)
-
-                    return string
-
-                colify(fmt(s) for s in specs)
-            # Print one entry per line if including flags
-            else:
-                for spec in specs:
-                    # Print the hash if necessary
-                    hsh = gray_hash(spec, hlen) + ' ' if hashes else ''
-                    print(hsh + spec.format(format_string, color=True) + '\n')
-
-        else:
-            raise ValueError(
-                "Invalid mode for display_specs: %s. Must be one of (paths,"
-                "deps, short)." % mode)  # NOQA: ignore=E501
-
-
 def query_arguments(args):
     # Check arguments
     if args.explicit and args.implicit:
diff --git a/lib/spack/spack/cmd/info.py b/lib/spack/spack/cmd/info.py
index 64d0d20e24..498518057b 100644
--- a/lib/spack/spack/cmd/info.py
+++ b/lib/spack/spack/cmd/info.py
@@ -29,9 +29,11 @@ import spack.fetch_strategy as fs
 
 description = "Get detailed information on a particular package"
 
+
 def padder(str_list, extra=0):
     """Return a function to pad elements of a list."""
     length = max(len(str(s)) for s in str_list) + extra
+
     def pad(string):
         string = str(string)
         padding = max(0, length - len(string))
@@ -40,7 +42,8 @@ def padder(str_list, extra=0):
 
 
 def setup_parser(subparser):
-    subparser.add_argument('name', metavar="PACKAGE", help="Name of package to get info for.")
+    subparser.add_argument(
+        'name', metavar="PACKAGE", help="Name of package to get info for.")
 
 
 def print_text_info(pkg):
@@ -81,12 +84,14 @@ def print_text_info(pkg):
 
             print "    " + fmt % (name, default, desc)
 
-    print
-    print "Dependencies:"
-    if pkg.dependencies:
-        colify(pkg.dependencies, indent=4)
-    else:
-        print "    None"
+    for deptype in ('build', 'link', 'run'):
+        print
+        print "%s Dependencies:" % deptype.capitalize()
+        deps = pkg.dependencies_of_type(deptype)
+        if deps:
+            colify(deps, indent=4)
+        else:
+            print "    None"
 
     print
     print "Virtual packages: "
diff --git a/lib/spack/spack/cmd/mirror.py b/lib/spack/spack/cmd/mirror.py
index d5f7abe212..0cf682fc4f 100644
--- a/lib/spack/spack/cmd/mirror.py
+++ b/lib/spack/spack/cmd/mirror.py
@@ -179,7 +179,7 @@ def mirror_create(args):
         new_specs = set()
         for spec in specs:
             spec.concretize()
-            for s in spec.traverse():
+            for s in spec.traverse(deptype_query=spack.alldeps):
                 new_specs.add(s)
         specs = list(new_specs)
 
diff --git a/lib/spack/spack/cmd/module.py b/lib/spack/spack/cmd/module.py
index 70da689b67..a10e36e077 100644
--- a/lib/spack/spack/cmd/module.py
+++ b/lib/spack/spack/cmd/module.py
@@ -23,135 +23,233 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
 from __future__ import print_function
+
+import collections
 import os
 import shutil
 import sys
 
 import llnl.util.tty as tty
 import spack.cmd
-from llnl.util.filesystem import mkdirp
+import spack.cmd.common.arguments as arguments
+import llnl.util.filesystem as filesystem
 from spack.modules import module_types
-from spack.util.string import *
-
-description = "Manipulate modules and dotkits."
-
-
-def setup_parser(subparser):
-    sp = subparser.add_subparsers(metavar='SUBCOMMAND', dest='module_command')
-
-    sp.add_parser('refresh', help='Regenerate all module files.')
 
-    find_parser = sp.add_parser('find', help='Find module files for packages.')
+description = "Manipulate module files"
 
-    find_parser.add_argument(
-        'module_type',
-        help="Type of module to find file for. [" +
-        '|'.join(module_types) + "]")
+# Dictionary that will be populated with the list of sub-commands
+# Each sub-command must be callable and accept 3 arguments :
+# - mtype : the type of the module file
+# - specs : the list of specs to be processed
+# - args : namespace containing the parsed command line arguments
+callbacks = {}
 
-    find_parser.add_argument(
-        '-r', '--dependencies', action='store_true',
-        dest='recurse_dependencies',
-        help='Recursively traverse dependencies for modules to load.')
 
-    find_parser.add_argument(
-        '-s', '--shell', action='store_true', dest='shell',
-        help='Generate shell script (instead of input for module command)')
+def subcommand(subparser_name):
+    """Registers a function in the callbacks dictionary"""
+    def decorator(callback):
+        callbacks[subparser_name] = callback
+        return callback
+    return decorator
 
-    find_parser.add_argument(
-        '-p', '--prefix', dest='prefix',
-        help='Prepend to module names when issuing module load commands')
 
-    find_parser.add_argument(
-        'spec', nargs='+',
-        help='spec to find a module file for.')
-
-
-def module_find(mtype, flags, spec_array):
-    """Look at all installed packages and see if the spec provided
-       matches any.  If it does, check whether there is a module file
-       of type <mtype> there, and print out the name that the user
-       should type to use that package's module.
-    prefix:
-        Prepend this to module names when issuing "module load" commands.
-        Some systems seem to need it.
+def setup_parser(subparser):
+    sp = subparser.add_subparsers(metavar='SUBCOMMAND', dest='subparser_name')
+
+    # spack module refresh
+    refresh_parser = sp.add_parser('refresh', help='Regenerate module files')
+    refresh_parser.add_argument(
+        '--delete-tree',
+        help='Delete the module file tree before refresh',
+        action='store_true'
+    )
+    arguments.add_common_arguments(
+        refresh_parser, ['constraint', 'module_type', 'yes_to_all']
+    )
+
+    # spack module find
+    find_parser = sp.add_parser('find', help='Find module files for packages')
+    arguments.add_common_arguments(find_parser, ['constraint', 'module_type'])
+
+    # spack module rm
+    rm_parser = sp.add_parser('rm', help='Remove module files')
+    arguments.add_common_arguments(
+        rm_parser, ['constraint', 'module_type', 'yes_to_all']
+    )
+
+    # spack module loads
+    loads_parser = sp.add_parser(
+        'loads',
+        help='Prompt the list of modules associated with a constraint'
+    )
+    loads_parser.add_argument(
+        '--input-only', action='store_false', dest='shell',
+        help='Generate input for module command (instead of a shell script)'
+    )
+    loads_parser.add_argument(
+        '-p', '--prefix', dest='prefix', default='',
+        help='Prepend to module names when issuing module load commands'
+    )
+    arguments.add_common_arguments(
+        loads_parser, ['constraint', 'module_type', 'recurse_dependencies']
+    )
+
+
+class MultipleMatches(Exception):
+    pass
+
+
+class NoMatch(Exception):
+    pass
+
+
+@subcommand('loads')
+def loads(mtype, specs, args):
+    """Prompt the list of modules associated with a list of specs"""
+    # Get a comprehensive list of specs
+    if args.recurse_dependencies:
+        specs_from_user_constraint = specs[:]
+        specs = []
+        # FIXME : during module file creation nodes seem to be visited
+        # FIXME : multiple times even if cover='nodes' is given. This
+        # FIXME : work around permits to get a unique list of spec anyhow.
+        # FIXME : (same problem as in spack/modules.py)
+        seen = set()
+        seen_add = seen.add
+        for spec in specs_from_user_constraint:
+            specs.extend(
+                [item for item in spec.traverse(order='post', cover='nodes') if not (item in seen or seen_add(item))]  # NOQA: ignore=E501
+            )
+
+    module_cls = module_types[mtype]
+    modules = [(spec, module_cls(spec).use_name)
+               for spec in specs if os.path.exists(module_cls(spec).file_name)]
+
+    module_commands = {
+        'tcl': 'module load ',
+        'dotkit': 'dotkit use '
+    }
+
+    d = {
+        'command': '' if not args.shell else module_commands[mtype],
+        'prefix': args.prefix
+    }
+
+    prompt_template = '{comment}{command}{prefix}{name}'
+    for spec, mod in modules:
+        d['comment'] = '' if not args.shell else '# {0}\n'.format(
+            spec.format())
+        d['name'] = mod
+        print(prompt_template.format(**d))
+
+
+@subcommand('find')
+def find(mtype, specs, args):
     """
-    if mtype not in module_types:
-        tty.die("Invalid module type: '%s'.  Options are %s" %
-                (mtype, comma_or(module_types)))
-
-    # --------------------------------------
-    def _find_modules(spec, modules_list):
-        """Finds all modules and sub-modules for a spec"""
-        if str(spec.version) == 'system':
-            # No Spack module for system-installed packages
-            return
-
-        if flags.recurse_dependencies:
-            for dep in spec.dependencies.values():
-                _find_modules(dep, modules_list)
-
-        mod = module_types[mtype](spec)
-        if not os.path.isfile(mod.file_name):
-            tty.die("No %s module is installed for %s" % (mtype, spec))
-        modules_list.append((spec, mod))
-
-
-    # --------------------------------------
-    raw_specs = spack.cmd.parse_specs(spec_array)
-    modules = set()    # Modules we will load
-    seen = set()
-    for raw_spec in raw_specs:
-
-        # ----------- Make sure the spec only resolves to ONE thing
-        specs = spack.installed_db.query(raw_spec)
-        if len(specs) == 0:
-            tty.die("No installed packages match spec %s" % raw_spec)
-
-        if len(specs) > 1:
-            tty.error("Multiple matches for spec %s.  Choose one:" % raw_spec)
-            for s in specs:
-                sys.stderr.write(s.tree(color=True))
-            sys.exit(1)
-        spec = specs[0]
-
-        # ----------- Chase down modules for it and all its dependencies
-        modules_dups = list()
-        _find_modules(spec, modules_dups)
-
-        # Remove duplicates while keeping order
-        modules_unique = list()
-        for spec,mod in modules_dups:
-            if mod.use_name not in seen:
-                modules_unique.append((spec,mod))
-                seen.add(mod.use_name)
-
-        # Output...
-        if flags.shell:
-            module_cmd = {'tcl': 'module load', 'dotkit': 'dotkit use'}[mtype]
-        for spec,mod in modules_unique:
-            if flags.shell:
-                print('# %s' % spec.format())
-                print('%s %s%s' % (module_cmd, flags.prefix, mod.use_name))
-            else:
-                print(mod.use_name)
-
-def module_refresh():
-    """Regenerate all module files for installed packages known to
-       spack (some packages may no longer exist)."""
-    specs = [s for s in spack.installed_db.query(installed=True, known=True)]
-
-    for name, cls in module_types.items():
-        tty.msg("Regenerating %s module files." % name)
-        if os.path.isdir(cls.path):
-            shutil.rmtree(cls.path, ignore_errors=False)
-        mkdirp(cls.path)
-        for spec in specs:
-            cls(spec).write()
+    Look at all installed packages and see if the spec provided
+    matches any.  If it does, check whether there is a module file
+    of type <mtype> there, and print out the name that the user
+    should type to use that package's module.
+    """
+    if len(specs) == 0:
+        raise NoMatch()
+
+    if len(specs) > 1:
+        raise MultipleMatches()
+
+    spec = specs.pop()
+    mod = module_types[mtype](spec)
+    if not os.path.isfile(mod.file_name):
+        tty.die("No %s module is installed for %s" % (mtype, spec))
+    print(mod.use_name)
+
+
+@subcommand('rm')
+def rm(mtype, specs, args):
+    """Deletes module files associated with items in specs"""
+    module_cls = module_types[mtype]
+    specs_with_modules = [
+        spec for spec in specs if os.path.exists(module_cls(spec).file_name)]
+    modules = [module_cls(spec) for spec in specs_with_modules]
+
+    if not modules:
+        tty.msg('No module file matches your query')
+        raise SystemExit(1)
+
+    # Ask for confirmation
+    if not args.yes_to_all:
+        tty.msg('You are about to remove {0} module files the following specs:\n'.format(mtype))  # NOQA: ignore=E501
+        spack.cmd.display_specs(specs_with_modules, long=True)
+        print('')
+        spack.cmd.ask_for_confirmation('Do you want to proceed ? ')
+
+    # Remove the module files
+    for s in modules:
+        s.remove()
+
+
+@subcommand('refresh')
+def refresh(mtype, specs, args):
+    """Regenerate module files for item in specs"""
+    # Prompt a message to the user about what is going to change
+    if not specs:
+        tty.msg('No package matches your query')
+        return
+
+    if not args.yes_to_all:
+        tty.msg('You are about to regenerate {name} module files for the following specs:\n'.format(name=mtype))  # NOQA: ignore=E501
+        spack.cmd.display_specs(specs, long=True)
+        print('')
+        spack.cmd.ask_for_confirmation('Do you want to proceed ? ')
+
+    cls = module_types[mtype]
+
+    # Detect name clashes
+    writers = [cls(spec) for spec in specs]
+    file2writer = collections.defaultdict(list)
+    for item in writers:
+        file2writer[item.file_name].append(item)
+
+    if len(file2writer) != len(writers):
+        message = 'Name clashes detected in module files:\n'
+        for filename, writer_list in file2writer.items():
+            if len(writer_list) > 1:
+                message += '\nfile : {0}\n'.format(filename)
+                for x in writer_list:
+                    message += 'spec : {0}\n'.format(x.spec.format(color=True))
+        tty.error(message)
+        tty.error('Operation aborted')
+        raise SystemExit(1)
+
+    # Proceed regenerating module files
+    tty.msg('Regenerating {name} module files'.format(name=mtype))
+    if os.path.isdir(cls.path) and args.delete_tree:
+        shutil.rmtree(cls.path, ignore_errors=False)
+    filesystem.mkdirp(cls.path)
+    for x in writers:
+        x.write(overwrite=True)
 
 
 def module(parser, args):
-    if args.module_command == 'refresh':
-        module_refresh()
-
-    elif args.module_command == 'find':
-        module_find(args.module_type, args, args.spec)
+    # Qualifiers to be used when querying the db for specs
+    constraint_qualifiers = {
+        'refresh': {
+            'installed': True,
+            'known': True
+        },
+    }
+    arguments.ConstraintAction.qualifiers.update(constraint_qualifiers)
+
+    module_type = args.module_type
+    constraint = args.constraint
+    try:
+        callbacks[args.subparser_name](module_type, args.specs, args)
+    except MultipleMatches:
+        message = 'the constraint \'{query}\' matches multiple packages, and this is not allowed in this context'  # NOQA: ignore=E501
+        tty.error(message.format(query=constraint))
+        for s in args.specs:
+            sys.stderr.write(s.format(color=True) + '\n')
+        raise SystemExit(1)
+    except NoMatch:
+        message = 'the constraint \'{query}\' match no package, and this is not allowed in this context'  # NOQA: ignore=E501
+        tty.die(message.format(query=constraint))
diff --git a/lib/spack/spack/cmd/package-list.py b/lib/spack/spack/cmd/package-list.py
index 6c5c4ae8c6..a27502d30e 100644
--- a/lib/spack/spack/cmd/package-list.py
+++ b/lib/spack/spack/cmd/package-list.py
@@ -22,10 +22,8 @@
 # License along with this program; if not, write to the Free Software
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
-import re
 import cgi
 from StringIO import StringIO
-import llnl.util.tty as tty
 from llnl.util.tty.colify import *
 import spack
 
@@ -34,21 +32,22 @@ description = "Print a list of all packages in reStructuredText."
 
 def github_url(pkg):
     """Link to a package file on github."""
-    return ("https://github.com/llnl/spack/blob/master/var/spack/packages/%s/package.py" %
-            pkg.name)
+    url = "https://github.com/llnl/spack/blob/master/var/spack/packages/%s/package.py"  # NOQA: ignore=E501
+    return (url % pkg.name)
 
 
 def rst_table(elts):
     """Print out a RST-style table."""
     cols = StringIO()
     ncol, widths = colify(elts, output=cols, tty=True)
-    header = " ".join("=" * (w-1) for w in widths)
+    header = " ".join("=" * (w - 1) for w in widths)
     return "%s\n%s%s" % (header, cols.getvalue(), header)
 
 
 def print_rst_package_list():
     """Print out information on all packages in restructured text."""
-    pkgs = sorted(spack.repo.all_packages(), key=lambda s:s.name.lower())
+    pkgs = sorted(spack.repo.all_packages(), key=lambda s: s.name.lower())
+    pkg_names = [p.name for p in pkgs]
 
     print ".. _package-list:"
     print
@@ -62,7 +61,7 @@ def print_rst_package_list():
 
     print "Spack currently has %d mainline packages:" % len(pkgs)
     print
-    print rst_table("`%s`_" % p.name for p in pkgs)
+    print rst_table("`%s`_" % p for p in pkg_names)
     print
     print "-----"
 
@@ -79,12 +78,17 @@ def print_rst_package_list():
         print
         if pkg.versions:
             print "Versions:"
-            print "  " + ", ".join(str(v) for v in reversed(sorted(pkg.versions)))
-        if pkg.dependencies:
-            print "Dependencies"
-            print "  " + ", ".join("`%s`_" % d if d != "mpi" else d
-                                   for d in pkg.dependencies)
-            print
+            print "  " + ", ".join(str(v) for v in
+                                   reversed(sorted(pkg.versions)))
+
+        for deptype in spack.alldeps:
+            deps = pkg.dependencies_of_type(deptype)
+            if deps:
+                print "%s Dependencies" % deptype.capitalize()
+                print "  " + ", ".join("%s_" % d if d in pkg_names
+                                       else d for d in deps)
+                print
+
         print "Description:"
         print pkg.format_doc(indent=2)
         print
diff --git a/lib/spack/spack/cmd/setup.py b/lib/spack/spack/cmd/setup.py
index 02e9bfd281..04f3d663df 100644
--- a/lib/spack/spack/cmd/setup.py
+++ b/lib/spack/spack/cmd/setup.py
@@ -44,7 +44,7 @@ def setup_parser(subparser):
         help="Display verbose build output while installing.")
     subparser.add_argument(
         'spec', nargs=argparse.REMAINDER,
-        help="specs to use for install.  Must contain package AND verison.")
+        help="specs to use for install.  Must contain package AND version.")
 
 
 def setup(self, args):
diff --git a/lib/spack/spack/cmd/test-install.py b/lib/spack/spack/cmd/test-install.py
index 45592a7dda..14c06d136d 100644
--- a/lib/spack/spack/cmd/test-install.py
+++ b/lib/spack/spack/cmd/test-install.py
@@ -133,7 +133,12 @@ def fetch_log(path):
 
 
 def failed_dependencies(spec):
-    return set(item for item in spec.dependencies.itervalues() if not spack.repo.get(item).installed)
+    def get_deps(deptype):
+        return set(item for item in spec.dependencies(deptype)
+                   if not spack.repo.get(item).installed)
+    link_deps = get_deps('link')
+    run_deps = get_deps('run')
+    return link_deps.union(run_deps)
 
 
 def get_top_spec_or_die(args):
diff --git a/lib/spack/spack/cmd/uninstall.py b/lib/spack/spack/cmd/uninstall.py
index a6f08d09ed..a17b7c685c 100644
--- a/lib/spack/spack/cmd/uninstall.py
+++ b/lib/spack/spack/cmd/uninstall.py
@@ -30,7 +30,6 @@ import llnl.util.tty as tty
 import spack
 import spack.cmd
 import spack.repository
-from spack.cmd.find import display_specs
 
 description = "Remove an installed package"
 
@@ -43,21 +42,10 @@ error_message = """You can either:
 display_args = {
     'long': True,
     'show_flags': True,
-    'variants':True
+    'variants': True
 }
 
 
-def ask_for_confirmation(message):
-    while True:
-        tty.msg(message + '[y/n]')
-        choice = raw_input().lower()
-        if choice == 'y':
-            break
-        elif choice == 'n':
-            raise SystemExit('Operation aborted')
-        tty.warn('Please reply either "y" or "n"')
-
-
 def setup_parser(subparser):
     subparser.add_argument(
         '-f', '--force', action='store_true', dest='force',
@@ -65,32 +53,37 @@ def setup_parser(subparser):
     subparser.add_argument(
         '-a', '--all', action='store_true', dest='all',
         help="USE CAREFULLY. Remove ALL installed packages that match each " +
-             "supplied spec. i.e., if you say uninstall libelf, ALL versions of " +
-             "libelf are uninstalled. This is both useful and dangerous, like rm -r.")
+             "supplied spec. i.e., if you say uninstall libelf, ALL versions of " +  # NOQA: ignore=E501
+             "libelf are uninstalled. This is both useful and dangerous, like rm -r.")  # NOQA: ignore=E501
     subparser.add_argument(
         '-d', '--dependents', action='store_true', dest='dependents',
-        help='Also uninstall any packages that depend on the ones given via command line.'
+        help='Also uninstall any packages that depend on the ones given via command line.'  # NOQA: ignore=E501
     )
     subparser.add_argument(
         '-y', '--yes-to-all', action='store_true', dest='yes_to_all',
-        help='Assume "yes" is the answer to every confirmation asked to the user.'
+        help='Assume "yes" is the answer to every confirmation asked to the user.'  # NOQA: ignore=E501
 
     )
-    subparser.add_argument('packages', nargs=argparse.REMAINDER, help="specs of packages to uninstall")
+    subparser.add_argument(
+        'packages',
+        nargs=argparse.REMAINDER,
+        help="specs of packages to uninstall"
+    )
 
 
 def concretize_specs(specs, allow_multiple_matches=False, force=False):
-    """
-    Returns a list of specs matching the non necessarily concretized specs given from cli
+    """Returns a list of specs matching the non necessarily
+    concretized specs given from cli
 
     Args:
         specs: list of specs to be matched against installed packages
-        allow_multiple_matches : boolean (if True multiple matches for each item in specs are admitted)
+        allow_multiple_matches : if True multiple matches are admitted
 
     Return:
         list of specs
     """
-    specs_from_cli = []  # List of specs that match expressions given via command line
+    # List of specs that match expressions given via command line
+    specs_from_cli = []
     has_errors = False
     for spec in specs:
         matching = spack.installed_db.query(spec)
@@ -99,7 +92,7 @@ def concretize_specs(specs, allow_multiple_matches=False, force=False):
         if not allow_multiple_matches and len(matching) > 1:
             tty.error("%s matches multiple packages:" % spec)
             print()
-            display_specs(matching, **display_args)
+            spack.cmd.display_specs(matching, **display_args)
             print()
             has_errors = True
 
@@ -116,8 +109,8 @@ def concretize_specs(specs, allow_multiple_matches=False, force=False):
 
 
 def installed_dependents(specs):
-    """
-    Returns a dictionary that maps a spec with a list of its installed dependents
+    """Returns a dictionary that maps a spec with a list of its
+    installed dependents
 
     Args:
         specs: list of specs to be checked for dependents
@@ -147,7 +140,7 @@ def do_uninstall(specs, force):
         try:
             # should work if package is known to spack
             packages.append(item.package)
-        except spack.repository.UnknownPackageError as e:
+        except spack.repository.UnknownPackageError:
             # The package.py file has gone away -- but still
             # want to uninstall.
             spack.Package(item).do_uninstall(force=True)
@@ -169,17 +162,20 @@ def uninstall(parser, args):
     with spack.installed_db.write_transaction():
         specs = spack.cmd.parse_specs(args.packages)
         # Gets the list of installed specs that match the ones give via cli
-        uninstall_list = concretize_specs(specs, args.all, args.force)  # takes care of '-a' is given in the cli
-        dependent_list = installed_dependents(uninstall_list)  # takes care of '-d'
+        # takes care of '-a' is given in the cli
+        uninstall_list = concretize_specs(specs, args.all, args.force)
+        dependent_list = installed_dependents(
+            uninstall_list)  # takes care of '-d'
 
         # Process dependent_list and update uninstall_list
         has_error = False
         if dependent_list and not args.dependents and not args.force:
             for spec, lst in dependent_list.items():
-                tty.error("Will not uninstall %s" % spec.format("$_$@$%@$#", color=True))
+                tty.error("Will not uninstall %s" %
+                          spec.format("$_$@$%@$#", color=True))
                 print('')
                 print("The following packages depend on it:")
-                display_specs(lst, **display_args)
+                spack.cmd.display_specs(lst, **display_args)
                 print('')
                 has_error = True
         elif args.dependents:
@@ -188,14 +184,14 @@ def uninstall(parser, args):
             uninstall_list = list(set(uninstall_list))
 
         if has_error:
-            tty.die('You can use spack uninstall --dependents to uninstall these dependencies as well')
+            tty.die('You can use spack uninstall --dependents to uninstall these dependencies as well')  # NOQA: ignore=E501
 
         if not args.yes_to_all:
             tty.msg("The following packages will be uninstalled : ")
             print('')
-            display_specs(uninstall_list, **display_args)
+            spack.cmd.display_specs(uninstall_list, **display_args)
             print('')
-            ask_for_confirmation('Do you want to proceed ? ')
+            spack.cmd.ask_for_confirmation('Do you want to proceed ? ')
 
         # Uninstall everything on the list
         do_uninstall(uninstall_list, args.force)
diff --git a/lib/spack/spack/concretize.py b/lib/spack/spack/concretize.py
index d9992a5680..386df08b2e 100644
--- a/lib/spack/spack/concretize.py
+++ b/lib/spack/spack/concretize.py
@@ -103,7 +103,7 @@ class DefaultConcretizer(object):
         usable.sort(cmp=cmp_externals)
         return usable
 
-
+    # XXX(deptypes): Look here.
     def choose_virtual_or_external(self, spec):
         """Given a list of candidate virtual and external packages, try to
            find one that is most ABI compatible.
@@ -394,8 +394,10 @@ def find_spec(spec, condition):
     """Searches the dag from spec in an intelligent order and looks
        for a spec that matches a condition"""
     # First search parents, then search children
-    dagiter = chain(spec.traverse(direction='parents',  root=False),
-                    spec.traverse(direction='children', root=False))
+    deptype = ('build', 'link')
+    dagiter = chain(
+            spec.traverse(direction='parents',  deptype=deptype, root=False),
+            spec.traverse(direction='children', deptype=deptype, root=False))
     visited = set()
     for relative in dagiter:
         if condition(relative):
@@ -403,7 +405,7 @@ def find_spec(spec, condition):
         visited.add(id(relative))
 
     # Then search all other relatives in the DAG *except* spec
-    for relative in spec.root.traverse():
+    for relative in spec.root.traverse(deptypes=spack.alldeps):
         if relative is spec: continue
         if id(relative) in visited: continue
         if condition(relative):
diff --git a/lib/spack/spack/config.py b/lib/spack/spack/config.py
index 84179e1469..8b5e96f97d 100644
--- a/lib/spack/spack/config.py
+++ b/lib/spack/spack/config.py
@@ -328,6 +328,11 @@ section_schemas = {
                 'anyOf': [
                     {
                         'properties': {
+                            'hash_length': {
+                                'type': 'integer',
+                                'minimum': 0,
+                                'default': 7
+                            },
                             'whitelist': {'$ref': '#/definitions/array_of_strings'},
                             'blacklist': {'$ref': '#/definitions/array_of_strings'},
                             'naming_scheme': {
@@ -492,8 +497,15 @@ class ConfigScope(object):
         """Empty cached config information."""
         self.sections = {}
 
+"""Default configuration scope is the lowest-level scope. These are
+   versioned with Spack and can be overridden by sites or users."""
+ConfigScope('defaults', os.path.join(spack.etc_path, 'spack', 'defaults'))
 
-ConfigScope('site', os.path.join(spack.etc_path, 'spack')),
+"""Site configuration is per spack instance, for sites or projects.
+   No site-level configs should be checked into spack by default."""
+ConfigScope('site', os.path.join(spack.etc_path, 'spack'))
+
+"""User configuration can override both spack defaults and site config."""
 ConfigScope('user', os.path.expanduser('~/.spack'))
 
 
diff --git a/lib/spack/spack/database.py b/lib/spack/spack/database.py
index a4bbff3d5a..317b0d5784 100644
--- a/lib/spack/spack/database.py
+++ b/lib/spack/spack/database.py
@@ -60,7 +60,7 @@ from spack.repository import UnknownPackageError
 _db_dirname = '.spack-db'
 
 # DB version.  This is stuck in the DB file to track changes in format.
-_db_version = Version('0.9.1')
+_db_version = Version('0.9.2')
 
 # Default timeout for spack database locks is 5 min.
 _db_lock_timeout = 60
@@ -215,9 +215,10 @@ class Database(object):
         # Add dependencies from other records in the install DB to
         # form a full spec.
         if 'dependencies' in spec_dict[spec.name]:
-            for dep_hash in spec_dict[spec.name]['dependencies'].values():
-                child = self._read_spec_from_yaml(dep_hash, installs, hash_key)
-                spec._add_dependency(child)
+            yaml_deps = spec_dict[spec.name]['dependencies']
+            for dname, dhash, dtypes in Spec.read_yaml_dep_specs(yaml_deps):
+                child = self._read_spec_from_yaml(dhash, installs, hash_key)
+                spec._add_dependency(child, dtypes)
 
         # Specs from the database need to be marked concrete because
         # they represent actual installations.
@@ -334,7 +335,10 @@ class Database(object):
         counts = {}
         for key, rec in self._data.items():
             counts.setdefault(key, 0)
-            for dep in rec.spec.dependencies.values():
+            # XXX(deptype): This checks all dependencies, but build
+            #               dependencies might be able to be dropped in the
+            #               future.
+            for dep in rec.spec.dependencies():
                 dep_key = dep.dag_hash()
                 counts.setdefault(dep_key, 0)
                 counts[dep_key] += 1
@@ -406,7 +410,7 @@ class Database(object):
         else:
             self._data[key] = InstallRecord(spec, path, True,
                                             explicit=explicit)
-            for dep in spec.dependencies.values():
+            for dep in spec.dependencies(('link', 'run')):
                 self._increment_ref_count(dep, directory_layout)
 
     def _increment_ref_count(self, spec, directory_layout=None):
@@ -421,7 +425,7 @@ class Database(object):
 
             self._data[key] = InstallRecord(spec.copy(), path, installed)
 
-            for dep in spec.dependencies.values():
+            for dep in spec.dependencies('link'):
                 self._increment_ref_count(dep)
 
         self._data[key].ref_count += 1
@@ -466,7 +470,7 @@ class Database(object):
 
         if rec.ref_count == 0 and not rec.installed:
             del self._data[key]
-            for dep in spec.dependencies.values():
+            for dep in spec.dependencies('link'):
                 self._decrement_ref_count(dep)
 
     def _remove(self, spec):
@@ -480,7 +484,7 @@ class Database(object):
             return rec.spec
 
         del self._data[key]
-        for dep in rec.spec.dependencies.values():
+        for dep in rec.spec.dependencies('link'):
             self._decrement_ref_count(dep)
 
         # Returns the concrete spec so we know it in the case where a
@@ -631,13 +635,14 @@ class WriteTransaction(_Transaction):
 class CorruptDatabaseError(SpackError):
     def __init__(self, path, msg=''):
         super(CorruptDatabaseError, self).__init__(
-            "Spack database is corrupt: %s.  %s." + \
-            "Try running `spack reindex` to fix." % (path, msg))
+            "Spack database is corrupt: %s.  %s." % (path, msg),
+            "Try running `spack reindex` to fix.")
 
 
 class InvalidDatabaseVersionError(SpackError):
     def __init__(self, expected, found):
         super(InvalidDatabaseVersionError, self).__init__(
-            "Expected database version %s but found version %s." + \
-            "Try running `spack reindex` to fix." %
-            (expected, found))
+            "Expected database version %s but found version %s."
+            % (expected, found),
+            "`spack reindex` may fix this, or you may need a newer "
+            "Spack version.")
diff --git a/lib/spack/spack/directives.py b/lib/spack/spack/directives.py
index ca8f21dc08..e92dd6fb67 100644
--- a/lib/spack/spack/directives.py
+++ b/lib/spack/spack/directives.py
@@ -171,7 +171,7 @@ def version(pkg, ver, checksum=None, **kwargs):
     pkg.versions[Version(ver)] = kwargs
 
 
-def _depends_on(pkg, spec, when=None):
+def _depends_on(pkg, spec, when=None, type=None):
     # If when is False do nothing
     if when is False:
         return
@@ -180,10 +180,29 @@ def _depends_on(pkg, spec, when=None):
         when = pkg.name
     when_spec = parse_anonymous_spec(when, pkg.name)
 
+    if type is None:
+        # The default deptype is build and link because the common case is to
+        # build against a library which then turns into a runtime dependency
+        # due to the linker.
+        # XXX(deptype): Add 'run' to this? It's an uncommon dependency type,
+        #               but is most backwards-compatible.
+        type = ('build', 'link')
+
+    if isinstance(type, str):
+        type = spack.spec.special_types.get(type, (type,))
+
+    for deptype in type:
+        if deptype not in spack.spec.alldeps:
+            raise UnknownDependencyTypeError('depends_on', pkg.name, deptype)
+
     dep_spec = Spec(spec)
     if pkg.name == dep_spec.name:
         raise CircularReferenceError('depends_on', pkg.name)
 
+    pkg_deptypes = pkg._deptypes.setdefault(dep_spec.name, set())
+    for deptype in type:
+        pkg_deptypes.add(deptype)
+
     conditions = pkg.dependencies.setdefault(dep_spec.name, {})
     if when_spec in conditions:
         conditions[when_spec].constrain(dep_spec, deps=False)
@@ -191,13 +210,13 @@ def _depends_on(pkg, spec, when=None):
         conditions[when_spec] = dep_spec
 
 
-@directive('dependencies')
-def depends_on(pkg, spec, when=None):
+@directive(('dependencies', '_deptypes'))
+def depends_on(pkg, spec, when=None, type=None):
     """Creates a dict of deps with specs defining when they apply."""
-    _depends_on(pkg, spec, when=when)
+    _depends_on(pkg, spec, when=when, type=type)
 
 
-@directive(('extendees', 'dependencies'))
+@directive(('extendees', 'dependencies', '_deptypes'))
 def extends(pkg, spec, **kwargs):
     """Same as depends_on, but dependency is symlinked into parent prefix.
 
@@ -326,3 +345,13 @@ class CircularReferenceError(DirectiveError):
             directive,
             "Package '%s' cannot pass itself to %s" % (package, directive))
         self.package = package
+
+
+class UnknownDependencyTypeError(DirectiveError):
+    """This is raised when a dependency is of an unknown type."""
+    def __init__(self, directive, package, deptype):
+        super(UnknownDependencyTypeError, self).__init__(
+            directive,
+            "Package '%s' cannot depend on a package via %s." %
+                (package, deptype))
+        self.package = package
diff --git a/lib/spack/spack/directory_layout.py b/lib/spack/spack/directory_layout.py
index ee13e2dcbc..8150a6da2b 100644
--- a/lib/spack/spack/directory_layout.py
+++ b/lib/spack/spack/directory_layout.py
@@ -34,6 +34,7 @@ import yaml
 import llnl.util.tty as tty
 from llnl.util.filesystem import join_path, mkdirp
 
+import spack
 from spack.spec import Spec
 from spack.error import SpackError
 
@@ -223,8 +224,14 @@ class YamlDirectoryLayout(DirectoryLayout):
 
     def read_spec(self, path):
         """Read the contents of a file and parse them as a spec"""
-        with open(path) as f:
-            spec = Spec.from_yaml(f)
+        try:
+            with open(path) as f:
+                spec = Spec.from_yaml(f)
+        except Exception as e:
+            if spack.debug:
+                raise
+            raise SpecReadError(
+                'Unable to read file: %s' % path, 'Cause: ' + str(e))
 
         # Specs read from actual installations are always concrete
         spec._mark_concrete()
@@ -285,7 +292,7 @@ class YamlDirectoryLayout(DirectoryLayout):
             return path
 
         if spec.dag_hash() == installed_spec.dag_hash():
-            raise SpecHashCollisionError(installed_hash, spec_hash)
+            raise SpecHashCollisionError(spec, installed_spec)
         else:
             raise InconsistentInstallDirectoryError(
                 'Spec file in %s does not match hash!' % spec_file_path)
@@ -431,7 +438,7 @@ class SpecHashCollisionError(DirectoryLayoutError):
     def __init__(self, installed_spec, new_spec):
         super(SpecHashCollisionError, self).__init__(
             'Specs %s and %s have the same SHA-1 prefix!'
-            % installed_spec, new_spec)
+            % (installed_spec, new_spec))
 
 
 class RemoveFailedError(DirectoryLayoutError):
@@ -456,10 +463,12 @@ class InstallDirectoryAlreadyExistsError(DirectoryLayoutError):
             "Install path %s already exists!")
 
 
+class SpecReadError(DirectoryLayoutError):
+    """Raised when directory layout can't read a spec."""
+
+
 class InvalidExtensionSpecError(DirectoryLayoutError):
     """Raised when an extension file has a bad spec in it."""
-    def __init__(self, message):
-        super(InvalidExtensionSpecError, self).__init__(message)
 
 
 class ExtensionAlreadyInstalledError(DirectoryLayoutError):
diff --git a/lib/spack/spack/graph.py b/lib/spack/spack/graph.py
index 22058d41d8..063e4647b6 100644
--- a/lib/spack/spack/graph.py
+++ b/lib/spack/spack/graph.py
@@ -80,12 +80,14 @@ def topological_sort(spec, **kwargs):
 
     """
     reverse = kwargs.get('reverse', False)
+    # XXX(deptype): iterate over a certain kind of dependency. Maybe color
+    #               edges based on the type of dependency?
     if not reverse:
-        parents  = lambda s: s.dependents
-        children = lambda s: s.dependencies
+        parents = lambda s: s.dependents()
+        children = lambda s: s.dependencies()
     else:
-        parents  = lambda s: s.dependencies
-        children = lambda s: s.dependents
+        parents = lambda s: s.dependencies()
+        children = lambda s: s.dependents()
 
     # Work on a copy so this is nondestructive.
     spec = spec.copy()
diff --git a/lib/spack/spack/modules.py b/lib/spack/spack/modules.py
index ce46047fa3..72656b8ae0 100644
--- a/lib/spack/spack/modules.py
+++ b/lib/spack/spack/modules.py
@@ -120,7 +120,7 @@ def dependencies(spec, request='all'):
         return []
 
     if request == 'direct':
-        return [xx for _, xx in spec.dependencies.items()]
+        return spec.dependencies()
 
     # FIXME : during module file creation nodes seem to be visited multiple
     # FIXME : times even if cover='nodes' is given. This work around permits
@@ -188,6 +188,8 @@ def parse_config_options(module_generator):
     #####
 
     # Automatic loading loads
+    module_file_actions['hash_length'] = module_configuration.get(
+        'hash_length', 7)
     module_file_actions['autoload'] = dependencies(
         module_generator.spec, module_file_actions.get('autoload', 'none'))
     # Prerequisites
@@ -237,6 +239,7 @@ class EnvModule(object):
     formats = {}
 
     class __metaclass__(type):
+
         def __init__(cls, name, bases, dict):
             type.__init__(cls, name, bases, dict)
             if cls.name != 'env_module' and cls.name in CONFIGURATION[
@@ -295,7 +298,9 @@ class EnvModule(object):
             if constraint in self.spec:
                 suffixes.append(suffix)
         # Always append the hash to make the module file unique
-        suffixes.append(self.spec.dag_hash())
+        hash_length = configuration.pop('hash_length', 7)
+        if hash_length != 0:
+            suffixes.append(self.spec.dag_hash(length=hash_length))
         name = '-'.join(suffixes)
         return name
 
@@ -338,7 +343,7 @@ class EnvModule(object):
 
         return False
 
-    def write(self):
+    def write(self, overwrite=False):
         """
         Writes out a module file for this object.
 
@@ -399,6 +404,15 @@ class EnvModule(object):
         for line in self.module_specific_content(module_configuration):
             module_file_content += line
 
+        # Print a warning in case I am accidentally overwriting
+        # a module file that is already there (name clash)
+        if not overwrite and os.path.exists(self.file_name):
+            message = 'Module file already exists : skipping creation\n'
+            message += 'file : {0.file_name}\n'
+            message += 'spec : {0.spec}'
+            tty.warn(message.format(self))
+            return
+
         # Dump to file
         with open(self.file_name, 'w') as f:
             f.write(module_file_content)
@@ -454,7 +468,7 @@ class EnvModule(object):
 
 class Dotkit(EnvModule):
     name = 'dotkit'
-
+    path = join_path(spack.share_path, 'dotkit')
     environment_modifications_formats = {
         PrependPath: 'dk_alter {name} {value}\n',
         SetEnv: 'dk_setenv {name} {value}\n'
@@ -466,7 +480,7 @@ class Dotkit(EnvModule):
 
     @property
     def file_name(self):
-        return join_path(spack.share_path, "dotkit", self.spec.architecture,
+        return join_path(self.path, self.spec.architecture,
                          '%s.dk' % self.use_name)
 
     @property
@@ -494,7 +508,7 @@ class Dotkit(EnvModule):
 
 class TclModule(EnvModule):
     name = 'tcl'
-
+    path = join_path(spack.share_path, "modules")
     environment_modifications_formats = {
         PrependPath: 'prepend-path --delim "{delim}" {name} \"{value}\"\n',
         AppendPath: 'append-path   --delim "{delim}" {name} \"{value}\"\n',
@@ -514,7 +528,7 @@ class TclModule(EnvModule):
 
     @property
     def file_name(self):
-        return join_path(spack.share_path, "modules", self.spec.architecture, self.use_name)
+        return join_path(self.path, self.spec.architecture, self.use_name)
 
     @property
     def header(self):
diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index 74008c4dd9..c916bfaaa2 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -37,7 +37,6 @@ import os
 import re
 import textwrap
 import time
-import glob
 import string
 
 import llnl.util.tty as tty
@@ -62,10 +61,10 @@ from llnl.util.tty.log import log_output
 from spack.stage import Stage, ResourceStage, StageComposite
 from spack.util.compression import allowed_archive
 from spack.util.environment import dump_environment
-from spack.util.executable import ProcessError, Executable, which
+from spack.util.executable import ProcessError, which
 from spack.version import *
 from spack import directory_layout
-from urlparse import urlparse
+
 
 """Allowed URL schemes for spack packages."""
 _ALLOWED_URL_SCHEMES = ["http", "https", "ftp", "file", "git"]
@@ -410,7 +409,6 @@ class Package(object):
         """Return the directory where the package.py file lives."""
         return os.path.dirname(self.module.__file__)
 
-
     @property
     def global_license_dir(self):
         """Returns the directory where global license files for all
@@ -565,6 +563,11 @@ class Package(object):
     def fetcher(self, f):
         self._fetcher = f
 
+    def dependencies_of_type(self, *deptypes):
+        """Get subset of the dependencies with certain types."""
+        return dict((name, conds) for name, conds in self.dependencies.items()
+                    if any(d in self._deptypes[name] for d in deptypes))
+
     @property
     def extendee_spec(self):
         """
@@ -577,7 +580,7 @@ class Package(object):
         name = next(iter(self.extendees))
 
         # If the extendee is in the spec's deps already, return that.
-        for dep in self.spec.traverse():
+        for dep in self.spec.traverse(deptypes=('link', 'run')):
             if name == dep.name:
                 return dep
 
@@ -642,12 +645,13 @@ class Package(object):
             yield self
 
         for name in sorted(self.dependencies.keys()):
-            spec = self.dependencies[name]
+            dep_spec = self.get_dependency(name)
+            spec = dep_spec.spec
 
-            # currently, we do not descend into virtual dependencies, as this
+            # Currently, we do not descend into virtual dependencies, as this
             # makes doing a sensible traversal much harder.  We just assume
             # that ANY of the virtual deps will work, which might not be true
-            # (due to conflicts or unsatisfiable specs).  For now this is ok
+            # (due to conflicts or unsatisfiable specs).  For now this is ok,
             # but we might want to reinvestigate if we start using a lot of
             # complicated virtual dependencies
             # TODO: reinvestigate this.
@@ -685,7 +689,9 @@ class Package(object):
         for spec in spack.installed_db.query():
             if self.name == spec.name:
                 continue
-            for dep in spec.traverse():
+            # XXX(deptype): Should build dependencies not count here?
+            # for dep in spec.traverse(deptype=('run')):
+            for dep in spec.traverse(deptype=spack.alldeps):
                 if self.spec == dep:
                     dependents.append(spec)
         return dependents
@@ -696,13 +702,13 @@ class Package(object):
         return self.spec.prefix
 
     @property
-    #TODO: Change this to architecture
+    # TODO: Change this to architecture
     def compiler(self):
         """Get the spack.compiler.Compiler object used to build this package"""
         if not self.spec.concrete:
             raise ValueError("Can only get a compiler for a concrete package.")
         return spack.compilers.compiler_for_spec(self.spec.compiler,
-                self.spec.architecture)
+                                                 self.spec.architecture)
 
     def url_version(self, version):
         """
@@ -758,7 +764,6 @@ class Package(object):
 
         self.stage.cache_local()
 
-
     def do_stage(self, mirror_only=False):
         """Unpacks the fetched tarball, then changes into the expanded tarball
            directory."""
@@ -876,6 +881,7 @@ class Package(object):
         return resource_stage_folder
 
     install_phases = set(['configure', 'build', 'install', 'provenance'])
+
     def do_install(self,
                    keep_prefix=False,
                    keep_stage=False,
@@ -887,7 +893,7 @@ class Package(object):
                    fake=False,
                    explicit=False,
                    dirty=False,
-                   install_phases = install_phases):
+                   install_phases=install_phases):
         """Called by commands to install a package and its dependencies.
 
         Package implementations should override install() to describe
@@ -908,7 +914,8 @@ class Package(object):
         run_tests   -- Runn tests within the package's install()
         """
         if not self.spec.concrete:
-            raise ValueError("Can only install concrete packages.")
+            raise ValueError("Can only install concrete packages: %s."
+                             % self.spec.name)
 
         # No installation needed if package is external
         if self.spec.external:
@@ -917,7 +924,8 @@ class Package(object):
             return
 
         # Ensure package is not already installed
-        if 'install' in install_phases and spack.install_layout.check_installed(self.spec):
+        layout = spack.install_layout
+        if 'install' in install_phases and layout.check_installed(self.spec):
             tty.msg("%s is already installed in %s" % (self.name, self.prefix))
             rec = spack.installed_db.get_record(self.spec)
             if (not rec.explicit) and explicit:
@@ -998,20 +1006,17 @@ class Package(object):
                     if 'install' in self.install_phases:
                         self.sanity_check_prefix()
 
-
                     # Copy provenance into the install directory on success
                     if 'provenance' in self.install_phases:
-                        log_install_path = spack.install_layout.build_log_path(
-                            self.spec)
-                        env_install_path = spack.install_layout.build_env_path(
-                            self.spec)
-                        packages_dir = spack.install_layout.build_packages_path(
-                            self.spec)
+                        log_install_path = layout.build_log_path(self.spec)
+                        env_install_path = layout.build_env_path(self.spec)
+                        packages_dir = layout.build_packages_path(self.spec)
 
                         # Remove first if we're overwriting another build
                         # (can happen with spack setup)
                         try:
-                            shutil.rmtree(packages_dir)   # log_install_path and env_install_path are inside this
+                            # log_install_path and env_install_path are here
+                            shutil.rmtree(packages_dir)
                         except:
                             pass
 
@@ -1038,7 +1043,7 @@ class Package(object):
         except directory_layout.InstallDirectoryAlreadyExistsError:
             if 'install' in install_phases:
                 # Abort install if install directory exists.
-                # But do NOT remove it (you'd be overwriting someon else's stuff)
+                # But do NOT remove it (you'd be overwriting someone's data)
                 tty.warn("Keeping existing install prefix in place.")
                 raise
             else:
@@ -1089,7 +1094,7 @@ class Package(object):
 
     def do_install_dependencies(self, **kwargs):
         # Pass along paths of dependencies here
-        for dep in self.spec.dependencies.values():
+        for dep in self.spec.dependencies():
             dep.package.do_install(**kwargs)
 
     @property
@@ -1270,7 +1275,7 @@ class Package(object):
                                   (self.name, self.extendee.name))
 
     def do_activate(self, force=False):
-        """Called on an etension to invoke the extendee's activate method.
+        """Called on an extension to invoke the extendee's activate method.
 
         Commands should call this routine, and should not call
         activate() directly.
@@ -1282,7 +1287,7 @@ class Package(object):
 
         # Activate any package dependencies that are also extensions.
         if not force:
-            for spec in self.spec.traverse(root=False):
+            for spec in self.spec.traverse(root=False, deptype='run'):
                 if spec.package.extends(self.extendee_spec):
                     if not spec.package.activated:
                         spec.package.do_activate(force=force)
@@ -1328,7 +1333,7 @@ class Package(object):
             for name, aspec in activated.items():
                 if aspec == self.spec:
                     continue
-                for dep in aspec.traverse():
+                for dep in aspec.traverse(deptype='run'):
                     if self.spec == dep:
                         raise ActivationError(
                             "Cannot deactivate %s because %s is activated and depends on it."  # NOQA: ignore=E501
@@ -1414,9 +1419,10 @@ class Package(object):
     def rpath(self):
         """Get the rpath this package links with, as a list of paths."""
         rpaths = [self.prefix.lib, self.prefix.lib64]
-        rpaths.extend(d.prefix.lib for d in self.spec.traverse(root=False)
+        deps = self.spec.dependencies(deptype='link')
+        rpaths.extend(d.prefix.lib for d in deps
                       if os.path.isdir(d.prefix.lib))
-        rpaths.extend(d.prefix.lib64 for d in self.spec.traverse(root=False)
+        rpaths.extend(d.prefix.lib64 for d in deps
                       if os.path.isdir(d.prefix.lib64))
         return rpaths
 
@@ -1433,6 +1439,13 @@ def install_dependency_symlinks(pkg, spec, prefix):
     flatten_dependencies(spec, prefix)
 
 
+def use_cray_compiler_names():
+    """Compiler names for builds that rely on cray compiler names."""
+    os.environ['CC'] = 'cc'
+    os.environ['CXX'] = 'CC'
+    os.environ['FC'] = 'ftn'
+    os.environ['F77'] = 'ftn'
+
 def flatten_dependencies(spec, flat_dir):
     """Make each dependency of spec present in dir via symlink."""
     for dep in spec.traverse(root=False):
@@ -1529,24 +1542,29 @@ def _hms(seconds):
         parts.append("%.2fs" % s)
     return ' '.join(parts)
 
+
 class StagedPackage(Package):
     """A Package subclass where the install() is split up into stages."""
 
     def install_setup(self):
-        """Creates an spack_setup.py script to configure the package later if we like."""
-        raise InstallError("Package %s provides no install_setup() method!" % self.name)
+        """Creates a spack_setup.py script to configure the package later."""
+        raise InstallError(
+            "Package %s provides no install_setup() method!" % self.name)
 
     def install_configure(self):
         """Runs the configure process."""
-        raise InstallError("Package %s provides no install_configure() method!" % self.name)
+        raise InstallError(
+            "Package %s provides no install_configure() method!" % self.name)
 
     def install_build(self):
         """Runs the build process."""
-        raise InstallError("Package %s provides no install_build() method!" % self.name)
+        raise InstallError(
+            "Package %s provides no install_build() method!" % self.name)
 
     def install_install(self):
         """Runs the install process."""
-        raise InstallError("Package %s provides no install_install() method!" % self.name)
+        raise InstallError(
+            "Package %s provides no install_install() method!" % self.name)
 
     def install(self, spec, prefix):
         if 'setup' in self.install_phases:
@@ -1563,9 +1581,10 @@ class StagedPackage(Package):
         else:
             # Create a dummy file so the build doesn't fail.
             # That way, the module file will also be created.
-            with open(os.path.join(prefix, 'dummy'), 'w') as fout:
+            with open(os.path.join(prefix, 'dummy'), 'w'):
                 pass
 
+
 # stackoverflow.com/questions/12791997/how-do-you-do-a-simple-chmod-x-from-within-python
 def make_executable(path):
     mode = os.stat(path).st_mode
@@ -1573,9 +1592,7 @@ def make_executable(path):
     os.chmod(path, mode)
 
 
-
 class CMakePackage(StagedPackage):
-
     def make_make(self):
         import multiprocessing
         # number of jobs spack will to build with.
@@ -1589,37 +1606,41 @@ class CMakePackage(StagedPackage):
         return make
 
     def configure_args(self):
-        """Returns package-specific arguments to be provided to the configure command."""
+        """Returns package-specific arguments to be provided to
+           the configure command.
+        """
         return list()
 
     def configure_env(self):
-        """Returns package-specific environment under which the configure command should be run."""
+        """Returns package-specific environment under which the
+           configure command should be run.
+        """
         return dict()
 
-    def spack_transitive_include_path(self):
+    def transitive_inc_path(self):
         return ';'.join(
             os.path.join(dep, 'include')
             for dep in os.environ['SPACK_DEPENDENCIES'].split(os.pathsep)
         )
 
     def install_setup(self):
-        cmd = [str(which('cmake'))] + \
-            spack.build_environment.get_std_cmake_args(self) + \
-            ['-DCMAKE_INSTALL_PREFIX=%s' % os.environ['SPACK_PREFIX'],
-            '-DCMAKE_C_COMPILER=%s' % os.environ['SPACK_CC'],
-            '-DCMAKE_CXX_COMPILER=%s' % os.environ['SPACK_CXX'],
-            '-DCMAKE_Fortran_COMPILER=%s' % os.environ['SPACK_FC']] + \
-            self.configure_args()
-
-        env = dict()
-        env['PATH'] = os.environ['PATH']
-        env['SPACK_TRANSITIVE_INCLUDE_PATH'] = self.spack_transitive_include_path()
-        env['CMAKE_PREFIX_PATH'] = os.environ['CMAKE_PREFIX_PATH']
+        cmd = [str(which('cmake'))]
+        cmd += spack.build_environment.get_std_cmake_args(self)
+        cmd += ['-DCMAKE_INSTALL_PREFIX=%s' % os.environ['SPACK_PREFIX'],
+                '-DCMAKE_C_COMPILER=%s' % os.environ['SPACK_CC'],
+                '-DCMAKE_CXX_COMPILER=%s' % os.environ['SPACK_CXX'],
+                '-DCMAKE_Fortran_COMPILER=%s' % os.environ['SPACK_FC']]
+        cmd += self.configure_args()
+
+        env = {
+            'PATH': os.environ['PATH'],
+            'SPACK_TRANSITIVE_INCLUDE_PATH': self.transitive_inc_path(),
+            'CMAKE_PREFIX_PATH': os.environ['CMAKE_PREFIX_PATH']
+        }
 
         setup_fname = 'spconfig.py'
         with open(setup_fname, 'w') as fout:
-            fout.write(\
-r"""#!%s
+            fout.write(r"""#!%s
 #
 
 import sys
@@ -1627,7 +1648,7 @@ import os
 import subprocess
 
 def cmdlist(str):
-	return list(x.strip().replace("'",'') for x in str.split('\n') if x)
+    return list(x.strip().replace("'",'') for x in str.split('\n') if x)
 env = dict(os.environ)
 """ % sys.executable)
 
@@ -1635,34 +1656,39 @@ env = dict(os.environ)
             for name in env_vars:
                 val = env[name]
                 if string.find(name, 'PATH') < 0:
-                    fout.write('env[%s] = %s\n' % (repr(name),repr(val)))
+                    fout.write('env[%s] = %s\n' % (repr(name), repr(val)))
                 else:
                     if name == 'SPACK_TRANSITIVE_INCLUDE_PATH':
                         sep = ';'
                     else:
                         sep = ':'
 
-                    fout.write('env[%s] = "%s".join(cmdlist("""\n' % (repr(name),sep))
+                    fout.write('env[%s] = "%s".join(cmdlist("""\n'
+                               % (repr(name), sep))
                     for part in string.split(val, sep):
                         fout.write('    %s\n' % part)
                     fout.write('"""))\n')
 
-            fout.write("env['CMAKE_TRANSITIVE_INCLUDE_PATH'] = env['SPACK_TRANSITIVE_INCLUDE_PATH']   # Deprecated\n")
+            fout.write("env['CMAKE_TRANSITIVE_INCLUDE_PATH'] = "
+                       "env['SPACK_TRANSITIVE_INCLUDE_PATH']   # Deprecated\n")
             fout.write('\ncmd = cmdlist("""\n')
             fout.write('%s\n' % cmd[0])
             for arg in cmd[1:]:
                 fout.write('    %s\n' % arg)
             fout.write('""") + sys.argv[1:]\n')
-            fout.write('\nproc = subprocess.Popen(cmd, env=env)\nproc.wait()\n')
+            fout.write('\nproc = subprocess.Popen(cmd, env=env)\n')
+            fout.write('proc.wait()\n')
         make_executable(setup_fname)
 
-
     def install_configure(self):
         cmake = which('cmake')
         with working_dir(self.build_directory, create=True):
-            os.environ.update(self.configure_env())
-            os.environ['SPACK_TRANSITIVE_INCLUDE_PATH'] = self.spack_transitive_include_path()
-            options = self.configure_args() + spack.build_environment.get_std_cmake_args(self)
+            env = os.environ
+            env.update(self.configure_env())
+            env['SPACK_TRANSITIVE_INCLUDE_PATH'] = self.transitive_inc_path()
+
+            options = self.configure_args()
+            options += spack.build_environment.get_std_cmake_args(self)
             cmake(self.source_directory, *options)
 
     def install_build(self):
diff --git a/lib/spack/spack/platforms/cray_xc.py b/lib/spack/spack/platforms/cray_xc.py
index e710303e23..2b065d5bbd 100644
--- a/lib/spack/spack/platforms/cray_xc.py
+++ b/lib/spack/spack/platforms/cray_xc.py
@@ -2,6 +2,8 @@ import os
 from spack.architecture import Platform, Target
 from spack.operating_systems.linux_distro import LinuxDistro
 from spack.operating_systems.cnl import Cnl
+from spack.util.executable import which
+
 
 class CrayXc(Platform):
     priority    = 20
@@ -9,9 +11,8 @@ class CrayXc(Platform):
     back_end    = 'ivybridge'
     default     = 'ivybridge'
 
-    front_os    = "SuSE11"
     back_os     = "CNL10"
-    default_os  = "CNL10" 
+    default_os  = "CNL10"
 
     def __init__(self):
         ''' Since cori doesn't have ivybridge as a front end it's better
@@ -32,15 +33,37 @@ class CrayXc(Platform):
         # Could switch to use modules and fe targets for front end
         # Currently using compilers by path for front end.
         self.add_target('sandybridge', Target('sandybridge'))
-        self.add_target('ivybridge', 
+        self.add_target('ivybridge',
                         Target('ivybridge', 'craype-ivybridge'))
-        self.add_target('haswell', 
-                        Target('haswell','craype-haswell'))         
+        self.add_target('haswell',
+                        Target('haswell', 'craype-haswell'))
 
-        self.add_operating_system('SuSE11', LinuxDistro())
+        # Front end of the cray platform is a linux distro.
+        linux_dist = LinuxDistro()
+        self.front_os = str(linux_dist)
+        self.add_operating_system(str(linux_dist), linux_dist)
         self.add_operating_system('CNL10', Cnl())
 
     @classmethod
-    def detect(self):
-        return os.path.exists('/opt/cray/craype')
+    def setup_platform_environment(self, pkg, env):
+        """ Change the linker to default dynamic to be more
+            similar to linux/standard linker behavior
+        """
+        env.set('CRAYPE_LINK_TYPE', 'dynamic')
+        cray_wrapper_names = join_path(spack.build_env_path, 'cray')
+        if os.path.isdir(cray_wrapper_names):
+            env.prepend_path('PATH', cray_wrapper_names)
 
+    @classmethod
+    def detect(self):
+        try:
+            cc_verbose = which('ftn')
+            text = cc_verbose('-craype-verbose',
+                              output=str, error=str,
+                              ignore_errors=True).split()
+            if '-D__CRAYXC' in text:
+                return True
+            else:
+                return False
+        except:
+            return False
diff --git a/lib/spack/spack/preferred_packages.py b/lib/spack/spack/preferred_packages.py
index 4820584150..1b94f03de7 100644
--- a/lib/spack/spack/preferred_packages.py
+++ b/lib/spack/spack/preferred_packages.py
@@ -26,8 +26,10 @@
 import spack
 from spack.version import *
 
+
 class PreferredPackages(object):
-    _default_order = {'compiler' : [ 'gcc', 'intel', 'clang', 'pgi', 'xlc' ] } # Arbitrary, but consistent
+    # Arbitrary, but consistent
+    _default_order = {'compiler': ['gcc', 'intel', 'clang', 'pgi', 'xlc']}
 
     def __init__(self):
         self.preferred = spack.config.get_config('packages')
@@ -35,24 +37,25 @@ class PreferredPackages(object):
 
     # Given a package name, sort component (e.g, version, compiler, ...), and
     # a second_key (used by providers), return the list
-    def _order_for_package(self, pkgname, component, second_key, test_all=True):
+    def _order_for_package(self, pkgname, component, second_key,
+                           test_all=True):
         pkglist = [pkgname]
         if test_all:
             pkglist.append('all')
         for pkg in pkglist:
             order = self.preferred.get(pkg, {}).get(component, {})
-            if type(order) is dict:
+            if isinstance(order, dict) and second_key:
                 order = order.get(second_key, {})
             if not order:
                 continue
             return [str(s).strip() for s in order]
         return []
 
-
     # A generic sorting function. Given a package name and sort
     # component, return less-than-0, 0, or greater-than-0 if
     # a is respectively less-than, equal to, or greater than b.
-    def _component_compare(self, pkgname, component, a, b, reverse_natural_compare, second_key):
+    def _component_compare(self, pkgname, component, a, b,
+                           reverse_natural_compare, second_key):
         if a is None:
             return -1
         if b is None:
@@ -84,92 +87,102 @@ class PreferredPackages(object):
         else:
             return 0
 
-
     # A sorting function for specs.  Similar to component_compare, but
     # a and b are considered to match entries in the sorting list if they
     # satisfy the list component.
-    def _spec_compare(self, pkgname, component, a, b, reverse_natural_compare, second_key):
-        if not a or not a.concrete:
+    def _spec_compare(self, pkgname, component, a, b,
+                      reverse_natural_compare, second_key):
+        if not a or (not a.concrete and not second_key):
             return -1
-        if not b or not b.concrete:
+        if not b or (not b.concrete and not second_key):
             return 1
         specs = self._spec_for_pkgname(pkgname, component, second_key)
         a_index = None
         b_index = None
         reverse = -1 if reverse_natural_compare else 1
         for i, cspec in enumerate(specs):
-            if a_index == None and (cspec.satisfies(a) or a.satisfies(cspec)):
+            if a_index is None and (cspec.satisfies(a) or a.satisfies(cspec)):
                 a_index = i
                 if b_index:
                     break
-            if b_index == None and (cspec.satisfies(b) or b.satisfies(cspec)):
+            if b_index is None and (cspec.satisfies(b) or b.satisfies(cspec)):
                 b_index = i
                 if a_index:
                     break
 
-        if   a_index != None and b_index == None: return -1
-        elif a_index == None and b_index != None: return 1
-        elif a_index != None and b_index == a_index: return -1 * cmp(a, b)
-        elif a_index != None and b_index != None and a_index != b_index: return cmp(a_index, b_index)
-        else: return cmp(a, b) * reverse
-
-
+        if a_index is not None and b_index is None:
+            return -1
+        elif a_index is None and b_index is not None:
+            return 1
+        elif a_index is not None and b_index == a_index:
+            return -1 * cmp(a, b)
+        elif (a_index is not None and b_index is not None and
+              a_index != b_index):
+            return cmp(a_index, b_index)
+        else:
+            return cmp(a, b) * reverse
 
     # Given a sort order specified by the pkgname/component/second_key, return
     # a list of CompilerSpecs, VersionLists, or Specs for that sorting list.
     def _spec_for_pkgname(self, pkgname, component, second_key):
         key = (pkgname, component, second_key)
-        if not key in self._spec_for_pkgname_cache:
+        if key not in self._spec_for_pkgname_cache:
             pkglist = self._order_for_package(pkgname, component, second_key)
             if not pkglist:
                 if component in self._default_order:
                     pkglist = self._default_order[component]
             if component == 'compiler':
-                self._spec_for_pkgname_cache[key] = [spack.spec.CompilerSpec(s) for s in pkglist]
+                self._spec_for_pkgname_cache[key] = \
+                    [spack.spec.CompilerSpec(s) for s in pkglist]
             elif component == 'version':
-                self._spec_for_pkgname_cache[key] = [VersionList(s) for s in pkglist]
+                self._spec_for_pkgname_cache[key] = \
+                    [VersionList(s) for s in pkglist]
             else:
-                self._spec_for_pkgname_cache[key] = [spack.spec.Spec(s) for s in pkglist]
+                self._spec_for_pkgname_cache[key] = \
+                    [spack.spec.Spec(s) for s in pkglist]
         return self._spec_for_pkgname_cache[key]
 
-
     def provider_compare(self, pkgname, provider_str, a, b):
-        """Return less-than-0, 0, or greater than 0 if a is respecively less-than, equal-to, or
-           greater-than b. A and b are possible implementations of provider_str.
-           One provider is less-than another if it is preferred over the other.
-           For example, provider_compare('scorep', 'mpi', 'mvapich', 'openmpi') would return -1 if
-           mvapich should be preferred over openmpi for scorep."""
-        return self._spec_compare(pkgname, 'providers', a, b, False, provider_str)
-
+        """Return less-than-0, 0, or greater than 0 if a is respecively
+           less-than, equal-to, or greater-than b. A and b are possible
+           implementations of provider_str. One provider is less-than another
+           if it is preferred over the other. For example,
+           provider_compare('scorep', 'mpi', 'mvapich', 'openmpi') would
+           return -1 if mvapich should be preferred over openmpi for scorep."""
+        return self._spec_compare(pkgname, 'providers', a, b, False,
+                                  provider_str)
 
     def spec_has_preferred_provider(self, pkgname, provider_str):
-        """Return True iff the named package has a list of preferred provider"""
-        return bool(self._order_for_package(pkgname, 'providers', provider_str, False))
-
+        """Return True iff the named package has a list of preferred
+           providers"""
+        return bool(self._order_for_package(pkgname, 'providers',
+                    provider_str, False))
 
     def version_compare(self, pkgname, a, b):
         """Return less-than-0, 0, or greater than 0 if version a of pkgname is
-           respecively less-than, equal-to, or greater-than version b of pkgname.
-           One version is less-than another if it is preferred over the other."""
+           respectively less-than, equal-to, or greater-than version b of
+           pkgname. One version is less-than another if it is preferred over
+           the other."""
         return self._spec_compare(pkgname, 'version', a, b, True, None)
 
-
     def variant_compare(self, pkgname, a, b):
         """Return less-than-0, 0, or greater than 0 if variant a of pkgname is
-           respecively less-than, equal-to, or greater-than variant b of pkgname.
-           One variant is less-than another if it is preferred over the other."""
+           respectively less-than, equal-to, or greater-than variant b of
+           pkgname. One variant is less-than another if it is preferred over
+           the other."""
         return self._component_compare(pkgname, 'variant', a, b, False, None)
 
-
     def architecture_compare(self, pkgname, a, b):
-        """Return less-than-0, 0, or greater than 0 if architecture a of pkgname is
-           respecively less-than, equal-to, or greater-than architecture b of pkgname.
-           One architecture is less-than another if it is preferred over the other."""
-        return self._component_compare(pkgname, 'architecture', a, b, False, None)
-
+        """Return less-than-0, 0, or greater than 0 if architecture a of pkgname
+           is respectively less-than, equal-to, or greater-than architecture b
+           of pkgname. One architecture is less-than another if it is preferred
+           over the other."""
+        return self._component_compare(pkgname, 'architecture', a, b,
+                                       False, None)
 
     def compiler_compare(self, pkgname, a, b):
         """Return less-than-0, 0, or greater than 0 if compiler a of pkgname is
-           respecively less-than, equal-to, or greater-than compiler b of pkgname.
-           One compiler is less-than another if it is preferred over the other."""
+           respecively less-than, equal-to, or greater-than compiler b of
+           pkgname. One compiler is less-than another if it is preferred over
+           the other."""
         return self._spec_compare(pkgname, 'compiler', a, b, False, None)
diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 77bc57147d..8bdae0445e 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -96,7 +96,6 @@ specs to avoid ambiguity.  Both are provided because ~ can cause shell
 expansion when it is the first character in an id typed on the command line.
 """
 import sys
-import itertools
 import hashlib
 import base64
 import imp
@@ -116,8 +115,6 @@ import spack.parse
 import spack.error
 import spack.compilers as compilers
 
-# TODO: move display_specs to some other location.
-from spack.cmd.find import display_specs
 from spack.version import *
 from spack.util.string import *
 from spack.util.prefix import Prefix
@@ -155,6 +152,14 @@ _separators = '[%s]' % ''.join(color_formats.keys())
    every time we call str()"""
 _any_version = VersionList([':'])
 
+# Special types of dependencies.
+alldeps = ('build', 'link', 'run')
+nolink = ('build', 'run')
+special_types = {
+    'alldeps': alldeps,
+    'nolink': nolink,
+}
+
 
 def index_specs(specs):
     """Take a list of specs and return a dict of lists.  Dict is
@@ -292,6 +297,32 @@ class CompilerSpec(object):
 
 
 @key_ordering
+class DependencySpec(object):
+    """Dependencies can be one (or more) of several types:
+
+    - build: needs to be in the PATH at build time.
+    - link: is linked to and added to compiler flags.
+    - run: needs to be in the PATH for the package to run.
+
+    Fields:
+    - spec: the spack.spec.Spec description of a dependency.
+    - deptypes: strings representing the type of dependency this is.
+    """
+    def __init__(self, spec, deptypes):
+        self.spec = spec
+        self.deptypes = deptypes
+
+    def _cmp_key(self):
+        return self.spec
+
+    def copy(self):
+        return DependencySpec(self.spec.copy(), self.deptype)
+
+    def __str__(self):
+        return str(self.spec)
+
+
+@key_ordering
 class VariantSpec(object):
 
     """Variants are named, build-time options for a package.  Names depend
@@ -440,11 +471,11 @@ class DependencyMap(HashableMap):
        The DependencyMap is keyed by name. """
     @property
     def concrete(self):
-        return all(d.concrete for d in self.values())
+        return all(d.spec.concrete for d in self.values())
 
     def __str__(self):
         return ''.join(
-            ["^" + str(self[name]) for name in sorted(self.keys())])
+            ["^" + str(self[name].spec) for name in sorted(self.keys())])
 
 
 @key_ordering
@@ -472,13 +503,13 @@ class Spec(object):
         # writes directly into this Spec object.
         other = spec_list[0]
         self.name = other.name
-        self.dependents = other.dependents
         self.versions = other.versions
         self.architecture = other.architecture
         self.compiler = other.compiler
         self.compiler_flags = other.compiler_flags
         self.compiler_flags.spec = self
-        self.dependencies = other.dependencies
+        self._dependencies = other._dependencies
+        self._dependents = other._dependents
         self.variants = other.variants
         self.variants.spec = self
         self.namespace = other.namespace
@@ -500,7 +531,50 @@ class Spec(object):
         # Spec(a, b) will copy a but just add b as a dep.
         for dep in dep_like:
             spec = dep if isinstance(dep, Spec) else Spec(dep)
-            self._add_dependency(spec)
+            # XXX(deptype): default deptypes
+            self._add_dependency(spec, ('build', 'link'))
+
+    def get_dependency(self, name):
+        dep = self._dependencies.get(name)
+        if dep is not None:
+            return dep
+        raise InvalidDependencyException(
+            self.name + " does not depend on " + comma_or(name))
+
+    def _deptype_norm(self, deptype):
+        if deptype is None:
+            return alldeps
+        # Force deptype to be a set object so that we can do set intersections.
+        if isinstance(deptype, str):
+            # Support special deptypes.
+            return special_types.get(deptype, (deptype,))
+        return deptype
+
+    def _find_deps(self, where, deptype):
+        deptype = self._deptype_norm(deptype)
+
+        return [dep.spec
+                for dep in where.values()
+                if deptype and any(d in deptype for d in dep.deptypes)]
+
+    def dependencies(self, deptype=None):
+        return self._find_deps(self._dependencies, deptype)
+
+    def dependents(self, deptype=None):
+        return self._find_deps(self._dependents, deptype)
+
+    def _find_deps_dict(self, where, deptype):
+        deptype = self._deptype_norm(deptype)
+
+        return dict((dep.spec.name, dep)
+                    for dep in where.values()
+                    if deptype and any(d in deptype for d in dep.deptypes))
+
+    def dependencies_dict(self, deptype=None):
+        return self._find_deps_dict(self._dependencies, deptype)
+
+    def dependents_dict(self, deptype=None):
+        return self._find_deps_dict(self._dependents, deptype)
 
     #
     # Private routines here are called by the parser when building a spec.
@@ -578,7 +652,8 @@ class Spec(object):
                 mod = imp.load_source(mod_name, path)
                 class_name = mod_to_class(value)
                 if not hasattr(mod, class_name):
-                    tty.die('No class %s defined in %s' % (class_name, mod_name))
+                    tty.die(
+                        'No class %s defined in %s' % (class_name, mod_name))
                 cls = getattr(mod, class_name)
                 if not inspect.isclass(cls):
                     tty.die('%s.%s is not a class' % (mod_name, class_name))
@@ -601,29 +676,32 @@ class Spec(object):
 
     def _set_os(self, value):
         """Called by the parser to set the architecture operating system"""
-        if self.architecture.platform:
-            self.architecture.platform_os = self.architecture.platform.operating_system(value)
+        arch = self.architecture
+        if arch.platform:
+            arch.platform_os = arch.platform.operating_system(value)
 
     def _set_target(self, value):
         """Called by the parser to set the architecture target"""
-        if self.architecture.platform:
-            self.architecture.target = self.architecture.platform.target(value)
+        arch = self.architecture
+        if arch.platform:
+            arch.target = arch.platform.target(value)
 
-    def _add_dependency(self, spec):
+    def _add_dependency(self, spec, deptypes):
         """Called by the parser to add another spec as a dependency."""
-        if spec.name in self.dependencies:
+        if spec.name in self._dependencies:
             raise DuplicateDependencyError(
                 "Cannot depend on '%s' twice" % spec)
-        self.dependencies[spec.name] = spec
-        spec.dependents[self.name] = self
+        self._dependencies[spec.name] = DependencySpec(spec, deptypes)
+        spec._dependents[self.name] = DependencySpec(self, deptypes)
 
     #
     # Public interface
     #
     @property
     def fullname(self):
-        return (('%s.%s' % (self.namespace, self.name)) if self.namespace else
-                           (self.name if self.name else ''))
+        return (
+            ('%s.%s' % (self.namespace, self.name)) if self.namespace else
+            (self.name if self.name else ''))
 
     @property
     def root(self):
@@ -632,15 +710,15 @@ class Spec(object):
            installed).  This will throw an assertion error if that is not
            the case.
         """
-        if not self.dependents:
+        if not self._dependents:
             return self
 
         # If the spec has multiple dependents, ensure that they all
         # lead to the same place.  Spack shouldn't deal with any DAGs
         # with multiple roots, so something's wrong if we find one.
-        depiter = iter(self.dependents.values())
-        first_root = next(depiter).root
-        assert(all(first_root is d.root for d in depiter))
+        depiter = iter(self._dependents.values())
+        first_root = next(depiter).spec.root
+        assert(all(first_root is d.spec.root for d in depiter))
         return first_root
 
     @property
@@ -679,18 +757,29 @@ class Spec(object):
         if self._concrete:
             return True
 
-        self._concrete = bool(not self.virtual
-                              and self.namespace is not None
-                              and self.versions.concrete
-                              and self.variants.concrete
-                              and self.architecture
-                              and self.architecture.concrete
-                              and self.compiler and self.compiler.concrete
-                              and self.compiler_flags.concrete
-                              and self.dependencies.concrete)
+        self._concrete = bool(not self.virtual and
+                              self.namespace is not None and
+                              self.versions.concrete and
+                              self.variants.concrete and
+                              self.architecture and
+                              self.architecture.concrete and
+                              self.compiler and self.compiler.concrete and
+                              self.compiler_flags.concrete and
+                              self._dependencies.concrete)
         return self._concrete
 
-    def traverse(self, visited=None, d=0, **kwargs):
+    def traverse(self, visited=None, deptype=None, **kwargs):
+        traversal = self.traverse_with_deptype(visited=visited,
+                                               deptype=deptype,
+                                               **kwargs)
+        if kwargs.get('depth', False):
+            return [(s[0], s[1].spec) for s in traversal]
+        else:
+            return [s.spec for s in traversal]
+
+    def traverse_with_deptype(self, visited=None, d=0, deptype=None,
+                              deptype_query=None, _self_deptype=None,
+                              **kwargs):
         """Generic traversal of the DAG represented by this spec.
            This will yield each node in the spec.  Options:
 
@@ -742,6 +831,12 @@ class Spec(object):
         direction = kwargs.get('direction', 'children')
         order = kwargs.get('order', 'pre')
 
+        if deptype is None:
+            deptype = alldeps
+
+        if deptype_query is None:
+            deptype_query = ('link', 'run')
+
         # Make sure kwargs have legal values; raise ValueError if not.
         def validate(name, val, allowed_values):
             if val not in allowed_values:
@@ -759,30 +854,37 @@ class Spec(object):
         if key in visited and cover == 'nodes':
             return
 
-        # Determine whether and what to yield for this node.
+        def return_val(res):
+            return (d, res) if depth else res
+
         yield_me = yield_root or d > 0
-        result = (d, self) if depth else self
 
         # Preorder traversal yields before successors
         if yield_me and order == 'pre':
-            yield result
+            yield return_val(DependencySpec(self, _self_deptype))
+
+        deps = self.dependencies_dict(deptype)
 
         # Edge traversal yields but skips children of visited nodes
         if not (key in visited and cover == 'edges'):
             # This code determines direction and yields the children/parents
-            successors = self.dependencies
+            successors = deps
             if direction == 'parents':
-                successors = self.dependents
+                successors = self.dependents_dict()
 
             visited.add(key)
             for name in sorted(successors):
                 child = successors[name]
-                for elt in child.traverse(visited, d + 1, **kwargs):
+                children = child.spec.traverse_with_deptype(
+                    visited, d=d + 1, deptype=deptype_query,
+                    deptype_query=deptype_query,
+                    _self_deptype=child.deptypes, **kwargs)
+                for elt in children:
                     yield elt
 
         # Postorder traversal yields after successors
         if yield_me and order == 'post':
-            yield result
+            yield return_val(DependencySpec(self, _self_deptype))
 
     @property
     def short_spec(self):
@@ -807,6 +909,7 @@ class Spec(object):
         if self._hash:
             return self._hash[:length]
         else:
+            # XXX(deptype): ignore 'build' dependencies here
             yaml_text = yaml.dump(
                 self.to_node_dict(), default_flow_style=True, width=sys.maxint)
             sha = hashlib.sha1(yaml_text)
@@ -819,11 +922,15 @@ class Spec(object):
         params = dict((name, v.value) for name, v in self.variants.items())
         params.update(dict((name, value)
                       for name, value in self.compiler_flags.items()))
+        deps = self.dependencies_dict(deptype=('link', 'run'))
         d = {
-            'parameters' : params,
-            'arch' : self.architecture,
-            'dependencies' : dict((d, self.dependencies[d].dag_hash())
-                                  for d in sorted(self.dependencies))
+            'parameters': params,
+            'arch': self.architecture,
+            'dependencies': dict(
+                (name, {
+                    'hash': dspec.spec.dag_hash(),
+                    'type': [str(s) for s in dspec.deptypes]})
+                for name, dspec in deps.items())
         }
 
         # Older concrete specs do not have a namespace.  Omit for
@@ -848,7 +955,7 @@ class Spec(object):
 
     def to_yaml(self, stream=None):
         node_list = []
-        for s in self.traverse(order='pre'):
+        for s in self.traverse(order='pre', deptype=('link', 'run')):
             node = s.to_node_dict()
             node[s.name]['hash'] = s.dag_hash()
             node_list.append(node)
@@ -889,9 +996,34 @@ class Spec(object):
             raise SpackRecordError(
                 "Did not find a valid format for variants in YAML file")
 
+        # Don't read dependencies here; from_node_dict() is used by
+        # from_yaml() to read the root *and* each dependency spec.
+
         return spec
 
     @staticmethod
+    def read_yaml_dep_specs(dependency_dict):
+        """Read the DependencySpec portion of a YAML-formatted Spec.
+
+        This needs to be backward-compatible with older spack spec
+        formats so that reindex will work on old specs/databases.
+        """
+        for dep_name, elt in dependency_dict.items():
+            if isinstance(elt, basestring):
+                # original format, elt is just the dependency hash.
+                dag_hash, deptypes = elt, ['build', 'link']
+            elif isinstance(elt, tuple):
+                # original deptypes format: (used tuples, not future-proof)
+                dag_hash, deptypes = elt
+            elif isinstance(elt, dict):
+                # new format: elements of dependency spec are keyed.
+                dag_hash, deptypes = elt['hash'], elt['type']
+            else:
+                raise SpecError("Couldn't parse dependency types in spec.")
+
+            yield dep_name, dag_hash, list(deptypes)
+
+    @staticmethod
     def from_yaml(stream):
         """Construct a spec from YAML.
 
@@ -902,25 +1034,30 @@ class Spec(object):
         represent more than the DAG does.
 
         """
-        deps = {}
-        spec = None
-
         try:
             yfile = yaml.load(stream)
         except MarkedYAMLError, e:
             raise SpackYAMLError("error parsing YAML spec:", str(e))
 
-        for node in yfile['spec']:
-            name = next(iter(node))
-            dep = Spec.from_node_dict(node)
-            if not spec:
-                spec = dep
-            deps[dep.name] = dep
+        nodes = yfile['spec']
+
+        # Read nodes out of list.  Root spec is the first element;
+        # dependencies are the following elements.
+        dep_list = [Spec.from_node_dict(node) for node in nodes]
+        if not dep_list:
+            raise SpecError("YAML spec contains no nodes.")
+        deps = dict((spec.name, spec) for spec in dep_list)
+        spec = dep_list[0]
 
-        for node in yfile['spec']:
+        for node in nodes:
+            # get dependency dict from the node.
             name = next(iter(node))
-            for dep_name in node[name]['dependencies']:
-                deps[name].dependencies[dep_name] = deps[dep_name]
+            yaml_deps = node[name]['dependencies']
+            for dname, dhash, dtypes in Spec.read_yaml_dep_specs(yaml_deps):
+                # Fill in dependencies by looking them up by name in deps dict
+                deps[name]._dependencies[dname] = DependencySpec(
+                    deps[dname], set(dtypes))
+
         return spec
 
     def _concretize_helper(self, presets=None, visited=None):
@@ -940,8 +1077,9 @@ class Spec(object):
         changed = False
 
         # Concretize deps first -- this is a bottom-up process.
-        for name in sorted(self.dependencies.keys()):
-            changed |= self.dependencies[name]._concretize_helper(presets, visited)
+        for name in sorted(self._dependencies.keys()):
+            changed |= self._dependencies[
+                name].spec._concretize_helper(presets, visited)
 
         if self.name in presets:
             changed |= self.constrain(presets[self.name])
@@ -965,13 +1103,16 @@ class Spec(object):
     def _replace_with(self, concrete):
         """Replace this virtual spec with a concrete spec."""
         assert(self.virtual)
-        for name, dependent in self.dependents.items():
+        for name, dep_spec in self._dependents.items():
+            dependent = dep_spec.spec
+            deptypes = dep_spec.deptypes
+
             # remove self from all dependents.
-            del dependent.dependencies[self.name]
+            del dependent._dependencies[self.name]
 
             # add the replacement, unless it is already a dep of dependent.
-            if concrete.name not in dependent.dependencies:
-                dependent._add_dependency(concrete)
+            if concrete.name not in dependent._dependencies:
+                dependent._add_dependency(concrete, deptypes)
 
     def _replace_node(self, replacement):
         """Replace this spec with another.
@@ -982,13 +1123,15 @@ class Spec(object):
         to be normalized.
 
         """
-        for name, dependent in self.dependents.items():
-            del dependent.dependencies[self.name]
-            dependent._add_dependency(replacement)
+        for name, dep_spec in self._dependents.items():
+            dependent = dep_spec.spec
+            deptypes = dep_spec.deptypes
+            del dependent._dependencies[self.name]
+            dependent._add_dependency(replacement, deptypes)
 
-        for name, dep in self.dependencies.items():
-            del dep.dependents[self.name]
-            del self.dependencies[dep.name]
+        for name, dep_spec in self._dependencies.items():
+            del dep_spec.spec.dependents[self.name]
+            del self._dependencies[dep.name]
 
     def _expand_virtual_packages(self):
         """Find virtual packages in this spec, replace them with providers,
@@ -1008,13 +1151,14 @@ class Spec(object):
               a problem.
         """
         # Make an index of stuff this spec already provides
+        # XXX(deptype): 'link' and 'run'?
         self_index = ProviderIndex(self.traverse(), restrict=True)
         changed = False
         done = False
 
         while not done:
             done = True
-
+            # XXX(deptype): 'link' and 'run'?
             for spec in list(self.traverse()):
                 replacement = None
                 if spec.virtual:
@@ -1054,24 +1198,26 @@ class Spec(object):
 
                 # If replacement is external then trim the dependencies
                 if replacement.external or replacement.external_module:
-                    if (spec.dependencies):
+                    if (spec._dependencies):
                         changed = True
-                        spec.dependencies = DependencyMap()
-                    replacement.dependencies = DependencyMap()
+                        spec._dependencies = DependencyMap()
+                    replacement._dependencies = DependencyMap()
                     replacement.architecture = self.architecture
 
                 # TODO: could this and the stuff in _dup be cleaned up?
                 def feq(cfield, sfield):
                     return (not cfield) or (cfield == sfield)
 
-                if replacement is spec or (feq(replacement.name, spec.name) and
-                    feq(replacement.versions, spec.versions) and
-                    feq(replacement.compiler, spec.compiler) and
-                    feq(replacement.architecture, spec.architecture) and
-                    feq(replacement.dependencies, spec.dependencies) and
-                    feq(replacement.variants, spec.variants) and
-                    feq(replacement.external, spec.external) and
-                    feq(replacement.external_module, spec.external_module)):
+                if replacement is spec or (
+                        feq(replacement.name, spec.name) and
+                        feq(replacement.versions, spec.versions) and
+                        feq(replacement.compiler, spec.compiler) and
+                        feq(replacement.architecture, spec.architecture) and
+                        feq(replacement._dependencies, spec._dependencies) and
+                        feq(replacement.variants, spec.variants) and
+                        feq(replacement.external, spec.external) and
+                        feq(replacement.external_module,
+                            spec.external_module)):
                     continue
                 # Refine this spec to the candidate. This uses
                 # replace_with AND dup so that it can work in
@@ -1116,7 +1262,7 @@ class Spec(object):
             changed = any(changes)
             force = True
 
-        for s in self.traverse():
+        for s in self.traverse(deptype_query=alldeps):
             # After concretizing, assign namespaces to anything left.
             # Note that this doesn't count as a "change".  The repository
             # configuration is constant throughout a spack run, and
@@ -1128,10 +1274,10 @@ class Spec(object):
             if s.namespace is None:
                 s.namespace = spack.repo.repo_for_pkg(s.name).namespace
 
-
         for s in self.traverse(root=False):
             if s.external_module:
-                compiler = spack.compilers.compiler_for_spec(s.compiler, s.architecture)
+                compiler = spack.compilers.compiler_for_spec(
+                    s.compiler, s.architecture)
                 for mod in compiler.modules:
                     load_module(mod)
 
@@ -1146,7 +1292,7 @@ class Spec(object):
         Only for internal use -- client code should use "concretize"
         unless there is a need to force a spec to be concrete.
         """
-        for s in self.traverse():
+        for s in self.traverse(deptype_query=alldeps):
             s._normal = True
             s._concrete = True
 
@@ -1159,6 +1305,13 @@ class Spec(object):
         return clone
 
     def flat_dependencies(self, **kwargs):
+        flat_deps = DependencyMap()
+        flat_deps_deptypes = self.flat_dependencies_with_deptype(**kwargs)
+        for name, depspec in flat_deps_deptypes.items():
+            flat_deps[name] = depspec.spec
+        return flat_deps
+
+    def flat_dependencies_with_deptype(self, **kwargs):
         """Return a DependencyMap containing all of this spec's
            dependencies with their constraints merged.
 
@@ -1169,23 +1322,31 @@ class Spec(object):
            returns them.
         """
         copy = kwargs.get('copy', True)
+        deptype_query = kwargs.get('deptype_query')
 
         flat_deps = DependencyMap()
         try:
-            for spec in self.traverse(root=False):
+            deptree = self.traverse_with_deptype(root=False,
+                                                 deptype_query=deptype_query)
+            for depspec in deptree:
+                spec = depspec.spec
+                deptypes = depspec.deptypes
+
                 if spec.name not in flat_deps:
                     if copy:
-                        flat_deps[spec.name] = spec.copy(deps=False)
+                        dep_spec = DependencySpec(spec.copy(deps=False),
+                                                  deptypes)
                     else:
-                        flat_deps[spec.name] = spec
+                        dep_spec = DependencySpec(spec, deptypes)
+                    flat_deps[spec.name] = dep_spec
                 else:
-                    flat_deps[spec.name].constrain(spec)
+                    flat_deps[spec.name].spec.constrain(spec)
 
             if not copy:
-                for dep in flat_deps.values():
-                    dep.dependencies.clear()
-                    dep.dependents.clear()
-                self.dependencies.clear()
+                for depspec in flat_deps.values():
+                    depspec.spec._dependencies.clear()
+                    depspec.spec._dependents.clear()
+                self._dependencies.clear()
 
             return flat_deps
 
@@ -1200,17 +1361,11 @@ class Spec(object):
         """Return DependencyMap that points to all the dependencies in this
            spec."""
         dm = DependencyMap()
+        # XXX(deptype): use a deptype kwarg.
         for spec in self.traverse():
             dm[spec.name] = spec
         return dm
 
-    def flatten(self):
-        """Pull all dependencies up to the root (this spec).
-           Merge constraints for dependencies with the same name, and if they
-           conflict, throw an exception. """
-        for dep in self.flat_dependencies(copy=False):
-            self._add_dependency(dep)
-
     def _evaluate_dependency_conditions(self, name):
         """Evaluate all the conditions on a dependency with this name.
 
@@ -1267,7 +1422,8 @@ class Spec(object):
             elif required:
                 raise UnsatisfiableProviderSpecError(required[0], vdep)
 
-    def _merge_dependency(self, dep, visited, spec_deps, provider_index):
+    def _merge_dependency(self, dep, deptypes, visited, spec_deps,
+                          provider_index):
         """Merge the dependency into this spec.
 
         This is the core of normalize().  There are some basic steps:
@@ -1294,7 +1450,9 @@ class Spec(object):
                 dep = provider
         else:
             index = ProviderIndex([dep], restrict=True)
-            for vspec in (v for v in spec_deps.values() if v.virtual):
+            for vspec in (v.spec
+                          for v in spec_deps.values()
+                          if v.spec.virtual):
                 if index.providers_for(vspec):
                     vspec._replace_with(dep)
                     del spec_deps[vspec.name]
@@ -1307,25 +1465,25 @@ class Spec(object):
         # If the spec isn't already in the set of dependencies, clone
         # it from the package description.
         if dep.name not in spec_deps:
-            spec_deps[dep.name] = dep.copy()
+            spec_deps[dep.name] = DependencySpec(dep.copy(), deptypes)
             changed = True
         # Constrain package information with spec info
         try:
-            changed |= spec_deps[dep.name].constrain(dep)
+            changed |= spec_deps[dep.name].spec.constrain(dep)
 
         except UnsatisfiableSpecError, e:
             e.message = "Invalid spec: '%s'. "
             e.message += "Package %s requires %s %s, but spec asked for %s"
-            e.message %= (spec_deps[dep.name], dep.name, e.constraint_type,
-                          e.required, e.provided)
+            e.message %= (spec_deps[dep.name].spec, dep.name,
+                          e.constraint_type, e.required, e.provided)
             raise e
 
         # Add merged spec to my deps and recurse
         dependency = spec_deps[dep.name]
-        if dep.name not in self.dependencies:
-            self._add_dependency(dependency)
+        if dep.name not in self._dependencies:
+            self._add_dependency(dependency.spec, dependency.deptypes)
 
-        changed |= dependency._normalize_helper(
+        changed |= dependency.spec._normalize_helper(
             visited, spec_deps, provider_index)
         return changed
 
@@ -1351,10 +1509,11 @@ class Spec(object):
             for dep_name in pkg.dependencies:
                 # Do we depend on dep_name?  If so pkg_dep is not None.
                 pkg_dep = self._evaluate_dependency_conditions(dep_name)
+                deptypes = pkg._deptypes[dep_name]
                 # If pkg_dep is a dependency, merge it.
                 if pkg_dep:
                     changed |= self._merge_dependency(
-                        pkg_dep, visited, spec_deps, provider_index)
+                        pkg_dep, deptypes, visited, spec_deps, provider_index)
             any_change |= changed
 
         return any_change
@@ -1385,11 +1544,13 @@ class Spec(object):
         # Ensure first that all packages & compilers in the DAG exist.
         self.validate_names()
         # Get all the dependencies into one DependencyMap
-        spec_deps = self.flat_dependencies(copy=False)
+        spec_deps = self.flat_dependencies_with_deptype(
+            copy=False, deptype_query=alldeps)
 
         # Initialize index of virtual dependency providers if
         # concretize didn't pass us one already
-        provider_index = ProviderIndex(spec_deps.values(), restrict=True)
+        provider_index = ProviderIndex(
+            [s.spec for s in spec_deps.values()], restrict=True)
 
         # traverse the package DAG and fill out dependencies according
         # to package files & their 'when' specs
@@ -1462,20 +1623,17 @@ class Spec(object):
                                                     other.variants[v])
 
         # TODO: Check out the logic here
-        if self.architecture is not None and other.architecture is not None:
-            if self.architecture.platform is not None and other.architecture.platform is not None:
-                if self.architecture.platform != other.architecture.platform:
-                    raise UnsatisfiableArchitectureSpecError(self.architecture,
-                                                             other.architecture)
-            if self.architecture.platform_os is not None and other.architecture.platform_os is not None:
-                if self.architecture.platform_os != other.architecture.platform_os:
-                    raise UnsatisfiableArchitectureSpecError(self.architecture,
-                                                             other.architecture)
-            if self.architecture.target is not None and other.architecture.target is not None:
-                if self.architecture.target != other.architecture.target:
-                    raise UnsatisfiableArchitectureSpecError(self.architecture,
-                                                             other.architecture)
-
+        sarch, oarch = self.architecture, other.architecture
+        if sarch is not None and oarch is not None:
+            if sarch.platform is not None and oarch.platform is not None:
+                if sarch.platform != oarch.platform:
+                    raise UnsatisfiableArchitectureSpecError(sarch, oarch)
+            if sarch.platform_os is not None and oarch.platform_os is not None:
+                if sarch.platform_os != oarch.platform_os:
+                    raise UnsatisfiableArchitectureSpecError(sarch, oarch)
+            if sarch.target is not None and oarch.target is not None:
+                if sarch.target != oarch.target:
+                    raise UnsatisfiableArchitectureSpecError(sarch, oarch)
 
         changed = False
         if self.compiler is not None and other.compiler is not None:
@@ -1490,15 +1648,16 @@ class Spec(object):
         changed |= self.compiler_flags.constrain(other.compiler_flags)
 
         old = str(self.architecture)
-        if self.architecture is None or other.architecture is None:
-            self.architecture = self.architecture or other.architecture
+        sarch, oarch = self.architecture, other.architecture
+        if sarch is None or other.architecture is None:
+            self.architecture = sarch or oarch
         else:
-            if self.architecture.platform is None or other.architecture.platform is None:
-                self.architecture.platform = self.architecture.platform or other.architecture.platform
-            if self.architecture.platform_os is None or other.architecture.platform_os is None:
-                self.architecture.platform_os = self.architecture.platform_os or other.architecture.platform_os
-            if self.architecture.target is None or other.architecture.target is None:
-                self.architecture.target = self.architecture.target or other.architecture.target
+            if sarch.platform is None or oarch.platform is None:
+                self.architecture.platform = sarch.platform or oarch.platform
+            if sarch.platform_os is None or oarch.platform_os is None:
+                sarch.platform_os = sarch.platform_os or oarch.platform_os
+            if sarch.target is None or oarch.target is None:
+                sarch.target = sarch.target or oarch.target
         changed |= (str(self.architecture) != old)
 
         if deps:
@@ -1510,7 +1669,7 @@ class Spec(object):
         """Apply constraints of other spec's dependencies to this spec."""
         other = self._autospec(other)
 
-        if not self.dependencies or not other.dependencies:
+        if not self._dependencies or not other._dependencies:
             return False
 
         # TODO: might want more detail than this, e.g. specific deps
@@ -1526,13 +1685,17 @@ class Spec(object):
 
         # Update with additional constraints from other spec
         for name in other.dep_difference(self):
-            self._add_dependency(other[name].copy())
+            dep_spec_copy = other.get_dependency(name)
+            dep_copy = dep_spec_copy.spec
+            deptypes = dep_spec_copy.deptypes
+            self._add_dependency(dep_copy.copy(), deptypes)
             changed = True
 
         return changed
 
     def common_dependencies(self, other):
         """Return names of dependencies that self an other have in common."""
+        # XXX(deptype): handle deptypes via deptype kwarg.
         common = set(
             s.name for s in self.traverse(root=False))
         common.intersection_update(
@@ -1625,15 +1788,25 @@ class Spec(object):
 
         # Architecture satisfaction is currently just string equality.
         # If not strict, None means unconstrained.
-        if self.architecture and other.architecture:
-            if ((self.architecture.platform and other.architecture.platform and self.architecture.platform != other.architecture.platform) or
-                (self.architecture.platform_os and other.architecture.platform_os and self.architecture.platform_os != other.architecture.platform_os) or
-                (self.architecture.target and other.architecture.target and self.architecture.target != other.architecture.target)):
+        sarch, oarch = self.architecture, other.architecture
+        if sarch and oarch:
+            if ((sarch.platform and
+                 oarch.platform and
+                 sarch.platform != oarch.platform) or
+
+                (sarch.platform_os and
+                 oarch.platform_os and
+                 sarch.platform_os != oarch.platform_os) or
+
+                (sarch.target and
+                 oarch.target and
+                 sarch.target != oarch.target)):
                 return False
-        elif strict and ((other.architecture and not self.architecture) or
-                         (other.architecture.platform and not self.architecture.platform) or
-                         (other.architecture.platform_os and not self.architecture.platform_os) or
-                         (other.architecture.target and not self.architecture.target)):
+
+        elif strict and ((oarch and not sarch) or
+                         (oarch.platform and not sarch.platform) or
+                         (oarch.platform_os and not sarch.platform_os) or
+                         (oarch.target and not sarch.target)):
             return False
 
         if not self.compiler_flags.satisfies(
@@ -1657,13 +1830,14 @@ class Spec(object):
         other = self._autospec(other)
 
         if strict:
-            if other.dependencies and not self.dependencies:
+            if other._dependencies and not self._dependencies:
                 return False
 
-            if not all(dep in self.dependencies for dep in other.dependencies):
+            if not all(dep in self._dependencies
+                       for dep in other._dependencies):
                 return False
 
-        elif not self.dependencies or not other.dependencies:
+        elif not self._dependencies or not other._dependencies:
             # if either spec doesn't restrict dependencies then both are
             # compatible.
             return True
@@ -1714,11 +1888,16 @@ class Spec(object):
         # We don't count dependencies as changes here
         changed = True
         if hasattr(self, 'name'):
-            changed = (self.name != other.name and self.versions != other.versions and \
-                       self.architecture != other.architecture and self.compiler != other.compiler and \
-                       self.variants != other.variants and self._normal != other._normal and \
-                       self.concrete != other.concrete and self.external != other.external and \
-                       self.external_module != other.external_module and self.compiler_flags != other.compiler_flags)
+            changed = (self.name != other.name and
+                       self.versions != other.versions and
+                       self.architecture != other.architecture and
+                       self.compiler != other.compiler and
+                       self.variants != other.variants and
+                       self._normal != other._normal and
+                       self.concrete != other.concrete and
+                       self.external != other.external and
+                       self.external_module != other.external_module and
+                       self.compiler_flags != other.compiler_flags)
 
         # Local node attributes get copied first.
         self.name = other.name
@@ -1726,8 +1905,8 @@ class Spec(object):
         self.architecture = other.architecture
         self.compiler = other.compiler.copy() if other.compiler else None
         if kwargs.get('cleardeps', True):
-            self.dependents = DependencyMap()
-            self.dependencies = DependencyMap()
+            self._dependents = DependencyMap()
+            self._dependencies = DependencyMap()
         self.compiler_flags = other.compiler_flags.copy()
         self.variants = other.variants.copy()
         self.variants.spec = self
@@ -1739,15 +1918,30 @@ class Spec(object):
         # If we copy dependencies, preserve DAG structure in the new spec
         if kwargs.get('deps', True):
             # This copies the deps from other using _dup(deps=False)
-            new_nodes = other.flat_dependencies()
+            # XXX(deptype): We can keep different instances of specs here iff
+            #               it is only a 'build' dependency (from its parent).
+            #               All other instances must be shared (due to symbol
+            #               and PATH contention). These should probably search
+            #               for any existing installation which can satisfy the
+            #               build and latch onto that because if 3 things need
+            #               the same build dependency and it is *not*
+            #               available, we only want to build it once.
+            new_nodes = other.flat_dependencies(deptype_query=alldeps)
             new_nodes[self.name] = self
 
-            # Hook everything up properly here by traversing.
-            for spec in other.traverse(cover='nodes'):
-                parent = new_nodes[spec.name]
-                for child in spec.dependencies:
-                    if child not in parent.dependencies:
-                        parent._add_dependency(new_nodes[child])
+            stack = [other]
+            while stack:
+                cur_spec = stack.pop(0)
+                new_spec = new_nodes[cur_spec.name]
+
+                for depspec in cur_spec._dependencies.values():
+                    stack.append(depspec.spec)
+
+                    # XXX(deptype): add any new deptypes that may have appeared
+                    #               here.
+                    if depspec.spec.name not in new_spec._dependencies:
+                        new_spec._add_dependency(
+                            new_nodes[depspec.spec.name], depspec.deptypes)
 
         # Since we preserved structure, we can copy _normal safely.
         self._normal = other._normal
@@ -1790,7 +1984,7 @@ class Spec(object):
         raise KeyError("No spec with name %s in %s" % (name, self))
 
     def __contains__(self, spec):
-        """True if this spec satisfis the provided spec, or if any dependency
+        """True if this spec satisfies the provided spec, or if any dependency
            does.  If the spec has no name, then we parse this one first.
         """
         spec = self._autospec(spec)
@@ -1814,13 +2008,13 @@ class Spec(object):
         if self.ne_node(other):
             return False
 
-        if len(self.dependencies) != len(other.dependencies):
+        if len(self._dependencies) != len(other._dependencies):
             return False
 
-        ssorted = [self.dependencies[name]
-                   for name in sorted(self.dependencies)]
-        osorted = [other.dependencies[name]
-                   for name in sorted(other.dependencies)]
+        ssorted = [self._dependencies[name].spec
+                   for name in sorted(self._dependencies)]
+        osorted = [other._dependencies[name].spec
+                   for name in sorted(other._dependencies)]
 
         for s, o in zip(ssorted, osorted):
             visited_s = id(s) in vs
@@ -1858,7 +2052,6 @@ class Spec(object):
                 self.compiler,
                 self.compiler_flags)
 
-
     def eq_node(self, other):
         """Equality with another spec, not including dependencies."""
         return self._cmp_node() == other._cmp_node()
@@ -1874,9 +2067,10 @@ class Spec(object):
           1. A tuple describing this node in the DAG.
           2. The hash of each of this node's dependencies' cmp_keys.
         """
+        dep_dict = self.dependencies_dict(deptype=('link', 'run'))
         return self._cmp_node() + (
-            tuple(hash(self.dependencies[name])
-                  for name in sorted(self.dependencies)),)
+            tuple(hash(dep_dict[name])
+                  for name in sorted(dep_dict)),)
 
     def colorized(self):
         return colorize_spec(self)
@@ -2053,41 +2247,39 @@ class Spec(object):
     def dep_string(self):
         return ''.join("^" + dep.format() for dep in self.sorted_deps())
 
-
     def __cmp__(self, other):
-        #Package name sort order is not configurable, always goes alphabetical
+        # Package name sort order is not configurable, always goes alphabetical
         if self.name != other.name:
             return cmp(self.name, other.name)
 
-        #Package version is second in compare order
+        # Package version is second in compare order
         pkgname = self.name
         if self.versions != other.versions:
-            return spack.pkgsort.version_compare(pkgname,
-                         self.versions, other.versions)
+            return spack.pkgsort.version_compare(
+                pkgname, self.versions, other.versions)
 
-        #Compiler is third
+        # Compiler is third
         if self.compiler != other.compiler:
-            return spack.pkgsort.compiler_compare(pkgname,
-                         self.compiler, other.compiler)
+            return spack.pkgsort.compiler_compare(
+                pkgname, self.compiler, other.compiler)
 
-        #Variants
+        # Variants
         if self.variants != other.variants:
-            return spack.pkgsort.variant_compare(pkgname,
-                         self.variants, other.variants)
+            return spack.pkgsort.variant_compare(
+                pkgname, self.variants, other.variants)
 
-        #Target
+        # Target
         if self.architecture != other.architecture:
-            return spack.pkgsort.architecture_compare(pkgname,
-                         self.architecture, other.architecture)
+            return spack.pkgsort.architecture_compare(
+                pkgname, self.architecture, other.architecture)
 
-        #Dependency is not configurable
-        if self.dependencies != other.dependencies:
-            return -1 if self.dependencies < other.dependencies else 1
+        # Dependency is not configurable
+        if self._dependencies != other._dependencies:
+            return -1 if self._dependencies < other._dependencies else 1
 
-        #Equal specs
+        # Equal specs
         return 0
 
-
     def __str__(self):
         return self.format() + self.dep_string()
 
@@ -2101,12 +2293,14 @@ class Spec(object):
         indent = kwargs.pop('indent', 0)
         fmt = kwargs.pop('format', '$_$@$%@+$+$=')
         prefix = kwargs.pop('prefix', None)
+        deptypes = kwargs.pop('deptypes', ('build', 'link'))
         check_kwargs(kwargs, self.tree)
 
         out = ""
         cur_id = 0
         ids = {}
-        for d, node in self.traverse(order='pre', cover=cover, depth=True):
+        for d, node in self.traverse(
+                order='pre', cover=cover, depth=True, deptypes=deptypes):
             if prefix is not None:
                 out += prefix(node)
             out += " " * indent
@@ -2160,8 +2354,8 @@ class SpecLexer(spack.parse.Lexer):
 # Lexer is always the same for every parser.
 _lexer = SpecLexer()
 
-class SpecParser(spack.parse.Parser):
 
+class SpecParser(spack.parse.Parser):
     def __init__(self):
         super(SpecParser, self).__init__(_lexer)
         self.previous = None
@@ -2196,10 +2390,13 @@ class SpecParser(spack.parse.Parser):
                         specs.append(self.spec(None))
                         self.previous = None
                     if self.accept(HASH):
-                        specs[-1]._add_dependency(self.spec_by_hash())
+                        dep = self.spec_by_hash()
                     else:
                         self.expect(ID)
-                        specs[-1]._add_dependency(self.spec(self.token.value))
+                        dep = self.spec(self.token.value)
+                    # XXX(deptype): default deptypes
+                    def_deptypes = ('build', 'link')
+                    specs[-1]._add_dependency(dep, def_deptypes)
 
                 else:
                     # Attempt to construct an anonymous spec, but check that
@@ -2211,8 +2408,8 @@ class SpecParser(spack.parse.Parser):
         except spack.parse.ParseError, e:
             raise SpecParseError(e)
 
-
-        # If the spec has an os or a target and no platform, give it the default platform
+        # If the spec has an os or a target and no platform, give it
+        # the default platform
         for spec in specs:
             for s in spec.traverse():
                 if s.architecture.os_string or s.architecture.target_string:
@@ -2263,8 +2460,8 @@ class SpecParser(spack.parse.Parser):
         spec.external = None
         spec.external_module = None
         spec.compiler_flags = FlagMap(spec)
-        spec.dependents = DependencyMap()
-        spec.dependencies = DependencyMap()
+        spec._dependents = DependencyMap()
+        spec._dependencies = DependencyMap()
         spec.namespace = spec_namespace
         spec._hash = None
 
diff --git a/lib/spack/spack/test/__init__.py b/lib/spack/spack/test/__init__.py
index fb91f24721..a849d5f350 100644
--- a/lib/spack/spack/test/__init__.py
+++ b/lib/spack/spack/test/__init__.py
@@ -32,15 +32,17 @@ from llnl.util.tty.colify import colify
 from spack.test.tally_plugin import Tally
 """Names of tests to be included in Spack's test suite"""
 
-test_names = ['architecture', 'versions', 'url_parse', 'url_substitution', 'packages', 'stage',
-              'spec_syntax', 'spec_semantics', 'spec_dag', 'concretize',
-              'multimethod', 'install', 'package_sanity', 'config',
-              'directory_layout', 'pattern', 'python_version', 'git_fetch',
-              'svn_fetch', 'hg_fetch', 'mirror', 'modules', 'url_extrapolate',
-              'cc', 'link_tree', 'spec_yaml', 'optional_deps',
-              'make_executable', 'configure_guess', 'lock', 'database',
-              'namespace_trie', 'yaml', 'sbang', 'environment', 'cmd.find',
-              'cmd.uninstall', 'cmd.test_install', 'cmd.test_compiler_cmd']
+test_names = [
+    'architecture', 'versions', 'url_parse', 'url_substitution', 'packages',
+    'stage', 'spec_syntax', 'spec_semantics', 'spec_dag', 'concretize',
+    'multimethod', 'install', 'package_sanity', 'config', 'directory_layout',
+    'pattern', 'python_version', 'git_fetch', 'svn_fetch', 'hg_fetch',
+    'mirror', 'modules', 'url_extrapolate', 'cc', 'link_tree', 'spec_yaml',
+    'optional_deps', 'make_executable', 'build_system_guess', 'lock',
+    'database', 'namespace_trie', 'yaml', 'sbang', 'environment', 'cmd.find',
+    'cmd.uninstall', 'cmd.test_install', 'cmd.test_compiler_cmd',
+    'cmd.module'
+]
 
 
 def list_tests():
diff --git a/lib/spack/spack/test/architecture.py b/lib/spack/spack/test/architecture.py
index ae3f08deed..09bdb021af 100644
--- a/lib/spack/spack/test/architecture.py
+++ b/lib/spack/spack/test/architecture.py
@@ -1,7 +1,31 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
 """ Test checks if the architecture class is created correctly and also that
     the functions are looking for the correct architecture name
 """
-import unittest
+import itertools
 import os
 import platform as py_platform
 import spack
@@ -14,9 +38,8 @@ from spack.platforms.darwin import Darwin
 
 from spack.test.mock_packages_test import *
 
-#class ArchitectureTest(unittest.TestCase):
-class ArchitectureTest(MockPackagesTest):
 
+class ArchitectureTest(MockPackagesTest):
     def setUp(self):
         super(ArchitectureTest, self).setUp()
         self.platform = spack.architecture.platform()
@@ -36,24 +59,22 @@ class ArchitectureTest(MockPackagesTest):
 
         self.assertEqual(arch, new_arch)
 
-        self.assertTrue( isinstance(arch, spack.architecture.Arch) )
-        self.assertTrue( isinstance(arch.platform, spack.architecture.Platform) )
-        self.assertTrue( isinstance(arch.platform_os,
-                                    spack.architecture.OperatingSystem) )
-        self.assertTrue( isinstance(arch.target,
-                                    spack.architecture.Target) )
-        self.assertTrue( isinstance(new_arch, spack.architecture.Arch) )
-        self.assertTrue( isinstance(new_arch.platform,
-                                    spack.architecture.Platform) )
-        self.assertTrue( isinstance(new_arch.platform_os,
-                                    spack.architecture.OperatingSystem) )
-        self.assertTrue( isinstance(new_arch.target,
-                                    spack.architecture.Target) )
-
+        self.assertTrue(isinstance(arch, spack.architecture.Arch))
+        self.assertTrue(isinstance(arch.platform, spack.architecture.Platform))
+        self.assertTrue(isinstance(arch.platform_os,
+                                   spack.architecture.OperatingSystem))
+        self.assertTrue(isinstance(arch.target,
+                                   spack.architecture.Target))
+        self.assertTrue(isinstance(new_arch, spack.architecture.Arch))
+        self.assertTrue(isinstance(new_arch.platform,
+                                   spack.architecture.Platform))
+        self.assertTrue(isinstance(new_arch.platform_os,
+                                   spack.architecture.OperatingSystem))
+        self.assertTrue(isinstance(new_arch.target,
+                                   spack.architecture.Target))
 
     def test_platform(self):
         output_platform_class = spack.architecture.platform()
-        my_arch_class = None
         if os.path.exists('/opt/cray/craype'):
             my_platform_class = CrayXc()
         elif os.path.exists('/bgsys'):
@@ -91,7 +112,7 @@ class ArchitectureTest(MockPackagesTest):
         default_os = self.platform.operating_system("default_os")
         default_target = self.platform.target("default_target")
 
-        default_spec = Spec("libelf") # default is no args
+        default_spec = Spec("libelf")  # default is no args
         default_spec.concretize()
         self.assertEqual(default_os, default_spec.architecture.platform_os)
         self.assertEqual(default_target, default_spec.architecture.target)
@@ -107,10 +128,11 @@ class ArchitectureTest(MockPackagesTest):
         combinations = itertools.product(os_list, target_list)
         results = []
         for arch in combinations:
-            o,t = arch
+            o, t = arch
             spec = Spec("libelf os=%s target=%s" % (o, t))
             spec.concretize()
-            results.append(spec.architecture.platform_os == self.platform.operating_system(o))
+            results.append(spec.architecture.platform_os ==
+                           self.platform.operating_system(o))
             results.append(spec.architecture.target == self.platform.target(t))
         res = all(results)
 
diff --git a/lib/spack/spack/test/configure_guess.py b/lib/spack/spack/test/build_system_guess.py
index bad3673e7a..e728a47cf4 100644
--- a/lib/spack/spack/test/configure_guess.py
+++ b/lib/spack/spack/test/build_system_guess.py
@@ -28,14 +28,14 @@ import tempfile
 import unittest
 
 from llnl.util.filesystem import *
-from spack.cmd.create import ConfigureGuesser
+from spack.cmd.create import BuildSystemGuesser
 from spack.stage import Stage
 from spack.test.mock_packages_test import *
 from spack.util.executable import which
 
 
 class InstallTest(unittest.TestCase):
-    """Tests the configure guesser in spack create"""
+    """Tests the build system guesser in spack create"""
 
     def setUp(self):
         self.tar = which('tar')
@@ -44,12 +44,10 @@ class InstallTest(unittest.TestCase):
         os.chdir(self.tmpdir)
         self.stage = None
 
-
     def tearDown(self):
         shutil.rmtree(self.tmpdir, ignore_errors=True)
         os.chdir(self.orig_dir)
 
-
     def check_archive(self, filename, system):
         mkdirp('archive')
         touch(join_path('archive', filename))
@@ -60,24 +58,24 @@ class InstallTest(unittest.TestCase):
         with Stage(url) as stage:
             stage.fetch()
 
-            guesser = ConfigureGuesser()
-            guesser(stage)
+            guesser = BuildSystemGuesser()
+            guesser(stage, url)
             self.assertEqual(system, guesser.build_system)
 
-
-    def test_python(self):
-        self.check_archive('setup.py', 'python')
-
-
     def test_autotools(self):
         self.check_archive('configure', 'autotools')
 
-
     def test_cmake(self):
         self.check_archive('CMakeLists.txt', 'cmake')
 
+    def test_scons(self):
+        self.check_archive('SConstruct', 'scons')
 
-    def test_unknown(self):
-        self.check_archive('foobar', 'unknown')
+    def test_python(self):
+        self.check_archive('setup.py', 'python')
 
+    def test_R(self):
+        self.check_archive('NAMESPACE', 'R')
 
+    def test_unknown(self):
+        self.check_archive('foobar', 'unknown')
diff --git a/lib/spack/spack/test/cmd/find.py b/lib/spack/spack/test/cmd/find.py
index 371e9650e0..fa82db7733 100644
--- a/lib/spack/spack/test/cmd/find.py
+++ b/lib/spack/spack/test/cmd/find.py
@@ -27,11 +27,7 @@
 import spack.cmd.find
 import unittest
 
-
-class Bunch(object):
-
-    def __init__(self, **kwargs):
-        self.__dict__.update(kwargs)
+from spack.util.pattern import Bunch
 
 
 class FindTest(unittest.TestCase):
diff --git a/lib/spack/spack/test/cmd/module.py b/lib/spack/spack/test/cmd/module.py
new file mode 100644
index 0000000000..36a4a73fe6
--- /dev/null
+++ b/lib/spack/spack/test/cmd/module.py
@@ -0,0 +1,83 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the LICENSE file for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+import argparse
+import os.path
+
+import spack.cmd.module as module
+import spack.modules as modules
+import spack.test.mock_database
+
+
+class TestModule(spack.test.mock_database.MockDatabase):
+
+    def _get_module_files(self, args):
+        return [
+            modules.module_types[args.module_type](spec).file_name for spec in args.specs  # NOQA: ignore=E501
+        ]
+
+    def test_module_common_operations(self):
+        parser = argparse.ArgumentParser()
+        module.setup_parser(parser)
+        # Try to remove a non existing module [tcl]
+        args = parser.parse_args(['rm', 'doesnotexist'])
+        self.assertRaises(SystemExit, module.module, parser, args)
+        # Remove existing modules [tcl]
+        args = parser.parse_args(['rm', '-y', 'mpileaks'])
+        module_files = self._get_module_files(args)
+        for item in module_files:
+            self.assertTrue(os.path.exists(item))
+        module.module(parser, args)
+        for item in module_files:
+            self.assertFalse(os.path.exists(item))
+        # Add them back [tcl]
+        args = parser.parse_args(['refresh', '-y', 'mpileaks'])
+        module.module(parser, args)
+        for item in module_files:
+            self.assertTrue(os.path.exists(item))
+        # TODO : test the --delete-tree option
+        # TODO : this requires having a separate directory for test modules
+        # Try to find a module with multiple matches
+        args = parser.parse_args(['find', 'mpileaks'])
+        self.assertRaises(SystemExit, module.module, parser, args)
+        # Try to find a module with no matches
+        args = parser.parse_args(['find', 'doesnotexist'])
+        self.assertRaises(SystemExit, module.module, parser, args)
+        # Try to find a module
+        args = parser.parse_args(['find', 'libelf'])
+        module.module(parser, args)
+        # Remove existing modules [dotkit]
+        args = parser.parse_args(['rm', '-y', '-m', 'dotkit', 'mpileaks'])
+        module_files = self._get_module_files(args)
+        for item in module_files:
+            self.assertTrue(os.path.exists(item))
+        module.module(parser, args)
+        for item in module_files:
+            self.assertFalse(os.path.exists(item))
+        # Add them back [dotkit]
+        args = parser.parse_args(['refresh', '-y', '-m', 'dotkit', 'mpileaks'])
+        module.module(parser, args)
+        for item in module_files:
+            self.assertTrue(os.path.exists(item))
+        # TODO : add tests for loads and find to check the prompt format
diff --git a/lib/spack/spack/test/cmd/test_install.py b/lib/spack/spack/test/cmd/test_install.py
index d17e013ed2..a94d3c8bba 100644
--- a/lib/spack/spack/test/cmd/test_install.py
+++ b/lib/spack/spack/test/cmd/test_install.py
@@ -58,16 +58,39 @@ test_install = __import__("spack.cmd.test-install", fromlist=['test_install'])
 
 class MockSpec(object):
     def __init__(self, name, version, hashStr=None):
-        self.dependencies = {}
+        self._dependencies = {}
         self.name = name
         self.version = version
         self.hash = hashStr if hashStr else hash((name, version))
 
+    def _deptype_norm(self, deptype):
+        if deptype is None:
+            return spack.alldeps
+        # Force deptype to be a tuple so that we can do set intersections.
+        if isinstance(deptype, str):
+            return (deptype,)
+        return deptype
+
+    def _find_deps(self, where, deptype):
+        deptype = self._deptype_norm(deptype)
+
+        return [dep.spec
+                for dep in where.values()
+                if deptype and any(d in deptype for d in dep.deptypes)]
+
+    def dependencies(self, deptype=None):
+        return self._find_deps(self._dependencies, deptype)
+
+    def dependents(self, deptype=None):
+        return self._find_deps(self._dependents, deptype)
+
     def traverse(self, order=None):
-        for _, spec in self.dependencies.items():
-            yield spec
+        for _, spec in self._dependencies.items():
+            yield spec.spec
         yield self
-        #allDeps = itertools.chain.from_iterable(i.traverse() for i in self.dependencies.itervalues())
+        #from_iterable = itertools.chain.from_iterable
+        #allDeps = from_iterable(i.traverse()
+        #                        for i in self.dependencies())
         #return set(itertools.chain([self], allDeps))
 
     def dag_hash(self):
@@ -104,7 +127,7 @@ def mock_fetch_log(path):
 
 specX = MockSpec('X', "1.2.0")
 specY = MockSpec('Y', "2.3.8")
-specX.dependencies['Y'] = specY
+specX._dependencies['Y'] = spack.DependencySpec(specY, spack.alldeps)
 pkgX = MockPackage(specX, 'logX')
 pkgY = MockPackage(specY, 'logY')
 
diff --git a/lib/spack/spack/test/concretize.py b/lib/spack/spack/test/concretize.py
index ce02b08bc3..ae3ceecfc8 100644
--- a/lib/spack/spack/test/concretize.py
+++ b/lib/spack/spack/test/concretize.py
@@ -197,32 +197,36 @@ class ConcretizeTest(MockPackagesTest):
     def test_virtual_is_fully_expanded_for_callpath(self):
         # force dependence on fake "zmpi" by asking for MPI 10.0
         spec = Spec('callpath ^mpi@10.0')
-        self.assertTrue('mpi' in spec.dependencies)
+        self.assertTrue('mpi' in spec._dependencies)
         self.assertFalse('fake' in spec)
 
         spec.concretize()
 
-        self.assertTrue('zmpi' in spec.dependencies)
-        self.assertTrue(all(not 'mpi' in d.dependencies for d in spec.traverse()))
+        self.assertTrue('zmpi' in spec._dependencies)
+        self.assertTrue(all('mpi' not in d._dependencies
+                            for d in spec.traverse()))
         self.assertTrue('zmpi' in spec)
         self.assertTrue('mpi' in spec)
 
-        self.assertTrue('fake' in spec.dependencies['zmpi'])
+        self.assertTrue('fake' in spec._dependencies['zmpi'].spec)
 
 
     def test_virtual_is_fully_expanded_for_mpileaks(self):
         spec = Spec('mpileaks ^mpi@10.0')
-        self.assertTrue('mpi' in spec.dependencies)
+        self.assertTrue('mpi' in spec._dependencies)
         self.assertFalse('fake' in spec)
 
         spec.concretize()
 
-        self.assertTrue('zmpi' in spec.dependencies)
-        self.assertTrue('callpath' in spec.dependencies)
-        self.assertTrue('zmpi' in spec.dependencies['callpath'].dependencies)
-        self.assertTrue('fake' in spec.dependencies['callpath'].dependencies['zmpi'].dependencies)
+        self.assertTrue('zmpi' in spec._dependencies)
+        self.assertTrue('callpath' in spec._dependencies)
+        self.assertTrue('zmpi' in spec._dependencies['callpath'].
+                                  spec._dependencies)
+        self.assertTrue('fake' in spec._dependencies['callpath'].
+                                  spec._dependencies['zmpi'].
+                                  spec._dependencies)
 
-        self.assertTrue(all(not 'mpi' in d.dependencies for d in spec.traverse()))
+        self.assertTrue(all(not 'mpi' in d._dependencies for d in spec.traverse()))
         self.assertTrue('zmpi' in spec)
         self.assertTrue('mpi' in spec)
 
diff --git a/lib/spack/spack/test/mock_packages_test.py b/lib/spack/spack/test/mock_packages_test.py
index c8b06cd7d7..9d96622a6e 100644
--- a/lib/spack/spack/test/mock_packages_test.py
+++ b/lib/spack/spack/test/mock_packages_test.py
@@ -191,8 +191,7 @@ class MockPackagesTest(unittest.TestCase):
         # restore later.
         self.saved_deps = {}
 
-
-    def set_pkg_dep(self, pkg_name, spec):
+    def set_pkg_dep(self, pkg_name, spec, deptypes=spack.alldeps):
         """Alters dependence information for a package.
 
         Adds a dependency on <spec> to pkg.
@@ -206,7 +205,9 @@ class MockPackagesTest(unittest.TestCase):
             self.saved_deps[pkg_name] = (pkg, pkg.dependencies.copy())
 
         # Change dep spec
-        pkg.dependencies[spec.name] = { Spec(pkg_name) : spec }
+        # XXX(deptype): handle deptypes.
+        pkg.dependencies[spec.name] = {Spec(pkg_name): spec}
+        pkg._deptypes[spec.name] = set(deptypes)
 
 
     def cleanmock(self):
@@ -216,6 +217,7 @@ class MockPackagesTest(unittest.TestCase):
         shutil.rmtree(self.temp_config, ignore_errors=True)
         spack.config.clear_config_caches()
 
+        # XXX(deptype): handle deptypes.
         # Restore dependency changes that happened during the test
         for pkg_name, (pkg, deps) in self.saved_deps.items():
             pkg.dependencies.clear()
diff --git a/lib/spack/spack/test/mock_repo.py b/lib/spack/spack/test/mock_repo.py
index a8098b8eec..386af282e7 100644
--- a/lib/spack/spack/test/mock_repo.py
+++ b/lib/spack/spack/test/mock_repo.py
@@ -103,6 +103,8 @@ class MockGitRepo(MockVCSRepo):
     def __init__(self):
         super(MockGitRepo, self).__init__('mock-git-stage', 'mock-git-repo')
 
+        self.url = 'file://' + self.path
+
         with working_dir(self.path):
             git('init')
 
@@ -140,8 +142,6 @@ class MockGitRepo(MockVCSRepo):
             self.r1      = self.rev_hash(self.branch)
             self.r1_file = self.branch_file
 
-            self.url = self.path
-
     def rev_hash(self, rev):
         return git('rev-parse', rev, output=str).strip()
 
diff --git a/lib/spack/spack/test/modules.py b/lib/spack/spack/test/modules.py
index 6d2e3705bd..135cd028e3 100644
--- a/lib/spack/spack/test/modules.py
+++ b/lib/spack/spack/test/modules.py
@@ -27,7 +27,6 @@ from contextlib import contextmanager
 
 import StringIO
 import spack.modules
-import unittest
 from spack.test.mock_packages_test import MockPackagesTest
 
 FILE_REGISTRY = collections.defaultdict(StringIO.StringIO)
@@ -266,7 +265,7 @@ class TclTests(MockPackagesTest):
 
     def test_blacklist(self):
         spack.modules.CONFIGURATION = configuration_blacklist
-        spec = spack.spec.Spec('mpileaks')
+        spec = spack.spec.Spec('mpileaks ^zmpi')
         content = self.get_modulefile_content(spec)
         self.assertEqual(len([x for x in content if 'is-loaded' in x]), 1)
         self.assertEqual(len([x for x in content if 'module load ' in x]), 1)
diff --git a/lib/spack/spack/test/spec_dag.py b/lib/spack/spack/test/spec_dag.py
index c56c70b1fe..972e79aa20 100644
--- a/lib/spack/spack/test/spec_dag.py
+++ b/lib/spack/spack/test/spec_dag.py
@@ -148,10 +148,12 @@ class SpecDagTest(MockPackagesTest):
         # Normalize then add conflicting constraints to the DAG (this is an
         # extremely unlikely scenario, but we test for it anyway)
         mpileaks.normalize()
-        mpileaks.dependencies['mpich'] = Spec('mpich@1.0')
-        mpileaks.dependencies['callpath'].dependencies['mpich'] = Spec('mpich@2.0')
+        mpileaks._dependencies['mpich'].spec = Spec('mpich@1.0')
+        mpileaks._dependencies['callpath']. \
+            spec._dependencies['mpich'].spec = Spec('mpich@2.0')
 
-        self.assertRaises(spack.spec.InconsistentSpecError, mpileaks.flatten)
+        self.assertRaises(spack.spec.InconsistentSpecError,
+                lambda: mpileaks.flat_dependencies(copy=False))
 
 
     def test_normalize_twice(self):
@@ -197,15 +199,17 @@ class SpecDagTest(MockPackagesTest):
 
     def check_links(self, spec_to_check):
         for spec in spec_to_check.traverse():
-            for dependent in spec.dependents.values():
+            for dependent in spec.dependents():
                 self.assertTrue(
-                    spec.name in dependent.dependencies,
-                    "%s not in dependencies of %s" % (spec.name, dependent.name))
+                    spec.name in dependent.dependencies_dict(),
+                    "%s not in dependencies of %s" %
+                        (spec.name, dependent.name))
 
-            for dependency in spec.dependencies.values():
+            for dependency in spec.dependencies():
                 self.assertTrue(
-                    spec.name in dependency.dependents,
-                    "%s not in dependents of %s" % (spec.name, dependency.name))
+                    spec.name in dependency.dependents_dict(),
+                    "%s not in dependents of %s" %
+                        (spec.name, dependency.name))
 
 
     def test_dependents_and_dependencies_are_correct(self):
@@ -442,3 +446,69 @@ class SpecDagTest(MockPackagesTest):
         orig_ids = set(id(s) for s in orig.traverse())
         copy_ids = set(id(s) for s in copy.traverse())
         self.assertFalse(orig_ids.intersection(copy_ids))
+
+    """
+    Here is the graph with deptypes labeled (assume all packages have a 'dt'
+    prefix). Arrows are marked with the deptypes ('b' for 'build', 'l' for
+    'link', 'r' for 'run').
+
+        use -bl-> top
+
+        top -b->  build1
+        top -bl-> link1
+        top -r->  run1
+
+        build1 -b->  build2
+        build1 -bl-> link2
+        build1 -r->  run2
+
+        link1 -bl-> link3
+
+        run1 -bl-> link5
+        run1 -r->  run3
+
+        link3 -b->  build2
+        link3 -bl-> link4
+
+        run3 -b-> build3
+    """
+    def test_deptype_traversal(self):
+        dag = Spec('dtuse')
+        dag.normalize()
+
+        names = ['dtuse', 'dttop', 'dtlink1', 'dtlink3', 'dtlink4',
+                 'dtrun1', 'dtlink5', 'dtrun3']
+
+        traversal = dag.traverse()
+        self.assertEqual([x.name for x in traversal], names)
+
+    def test_deptype_traversal_with_builddeps(self):
+        dag = Spec('dttop')
+        dag.normalize()
+
+        names = ['dttop', 'dtbuild1', 'dtlink2', 'dtrun2', 'dtlink1',
+                 'dtlink3', 'dtlink4', 'dtrun1', 'dtlink5', 'dtrun3']
+
+        traversal = dag.traverse()
+        self.assertEqual([x.name for x in traversal], names)
+
+    def test_deptype_traversal_full(self):
+        dag = Spec('dttop')
+        dag.normalize()
+
+        names = ['dttop', 'dtbuild1', 'dtbuild2', 'dtlink2', 'dtrun2',
+                 'dtlink1', 'dtlink3', 'dtlink4', 'dtrun1', 'dtlink5',
+                 'dtrun3', 'dtbuild3']
+
+        traversal = dag.traverse(deptype_query=spack.alldeps)
+        self.assertEqual([x.name for x in traversal], names)
+
+    def test_deptype_traversal_pythonpath(self):
+        dag = Spec('dttop')
+        dag.normalize()
+
+        names = ['dttop', 'dtbuild1', 'dtrun2', 'dtlink1', 'dtrun1',
+                 'dtrun3']
+
+        traversal = dag.traverse(deptype=spack.nolink, deptype_query='run')
+        self.assertEqual([x.name for x in traversal], names)
diff --git a/lib/spack/spack/test/stage.py b/lib/spack/spack/test/stage.py
index 6d8c3ac67c..d3e3bf1383 100644
--- a/lib/spack/spack/test/stage.py
+++ b/lib/spack/spack/test/stage.py
@@ -35,8 +35,8 @@ from llnl.util.filesystem import *
 from spack.stage import Stage
 from spack.util.executable import which
 
-test_files_dir = join_path(spack.stage_path, '.test')
-test_tmp_path  = join_path(test_files_dir, 'tmp')
+test_files_dir = os.path.realpath(join_path(spack.stage_path, '.test'))
+test_tmp_path  = os.path.realpath(join_path(test_files_dir, 'tmp'))
 
 archive_dir      = 'test-files'
 archive_name     = archive_dir + '.tar.gz'
diff --git a/lib/spack/spack/util/pattern.py b/lib/spack/spack/util/pattern.py
index 6d4bcb1039..bc5e9d2ffe 100644
--- a/lib/spack/spack/util/pattern.py
+++ b/lib/spack/spack/util/pattern.py
@@ -28,42 +28,50 @@ import functools
 
 
 def composite(interface=None, method_list=None, container=list):
-    """
-    Returns a class decorator that patches a class adding all the methods it needs to be a composite for a given
-    interface.
+    """Returns a class decorator that patches a class adding all the methods
+    it needs to be a composite for a given interface.
 
-    :param interface: class exposing the interface to which the composite object must conform. Only non-private and
-    non-special methods will be taken into account
+    :param interface: class exposing the interface to which the composite
+    object must conform. Only non-private and non-special methods will be
+    taken into account
 
     :param method_list: names of methods that should be part of the composite
 
-    :param container: container for the composite object (default = list). Must fulfill the MutableSequence contract.
-    The composite class will expose the container API to manage object composition
+    :param container: container for the composite object (default = list).
+    Must fulfill the MutableSequence contract. The composite class will expose
+    the container API to manage object composition
 
     :return: class decorator
     """
-    # Check if container fulfills the MutableSequence contract and raise an exception if it doesn't
-    # The patched class returned by the decorator will inherit from the container class to expose the
-    # interface needed to manage objects composition
+    # Check if container fulfills the MutableSequence contract and raise an
+    # exception if it doesn't. The patched class returned by the decorator will
+    # inherit from the container class to expose the interface needed to manage
+    # objects composition
     if not issubclass(container, collections.MutableSequence):
         raise TypeError("Container must fulfill the MutableSequence contract")
 
-    # Check if at least one of the 'interface' or the 'method_list' arguments are defined
+    # Check if at least one of the 'interface' or the 'method_list' arguments
+    # are defined
     if interface is None and method_list is None:
-        raise TypeError("Either 'interface' or 'method_list' must be defined on a call to composite")
+        raise TypeError("Either 'interface' or 'method_list' must be defined on a call to composite")  # NOQA : ignore=E501
 
     def cls_decorator(cls):
-        # Retrieve the base class of the composite. Inspect its methods and decide which ones will be overridden
+        # Retrieve the base class of the composite. Inspect its methods and
+        # decide which ones will be overridden
         def no_special_no_private(x):
             return inspect.ismethod(x) and not x.__name__.startswith('_')
 
-        # Patch the behavior of each of the methods in the previous list. This is done associating an instance of the
-        # descriptor below to any method that needs to be patched.
+        # Patch the behavior of each of the methods in the previous list.
+        # This is done associating an instance of the descriptor below to
+        # any method that needs to be patched.
         class IterateOver(object):
+            """Decorator used to patch methods in a composite.
+
+            It iterates over all the items in the instance containing the
+            associated attribute and calls for each of them an attribute
+            with the same name
             """
-            Decorator used to patch methods in a composite. It iterates over all the items in the instance containing the
-            associated attribute and calls for each of them an attribute with the same name
-            """
+
             def __init__(self, name, func=None):
                 self.name = name
                 self.func = func
@@ -72,8 +80,9 @@ def composite(interface=None, method_list=None, container=list):
                 def getter(*args, **kwargs):
                     for item in instance:
                         getattr(item, self.name)(*args, **kwargs)
-                # If we are using this descriptor to wrap a method from an interface, then we must conditionally
-                # use the `functools.wraps` decorator to set the appropriate fields.
+                # If we are using this descriptor to wrap a method from an
+                # interface, then we must conditionally use the
+                # `functools.wraps` decorator to set the appropriate fields
                 if self.func is not None:
                     getter = functools.wraps(self.func)(getter)
                 return getter
@@ -81,7 +90,8 @@ def composite(interface=None, method_list=None, container=list):
         dictionary_for_type_call = {}
         # Construct a dictionary with the methods explicitly passed as name
         if method_list is not None:
-            # python@2.7: method_list_dict = {name: IterateOver(name) for name in method_list}
+            # python@2.7: method_list_dict = {name: IterateOver(name) for name
+            # in method_list}
             method_list_dict = {}
             for name in method_list:
                 method_list_dict[name] = IterateOver(name)
@@ -89,28 +99,40 @@ def composite(interface=None, method_list=None, container=list):
         # Construct a dictionary with the methods inspected from the interface
         if interface is not None:
             ##########
-            # python@2.7: interface_methods = {name: method for name, method in inspect.getmembers(interface, predicate=no_special_no_private)}
+            # python@2.7: interface_methods = {name: method for name, method in
+            # inspect.getmembers(interface, predicate=no_special_no_private)}
             interface_methods = {}
-            for name, method in inspect.getmembers(interface, predicate=no_special_no_private):
+            for name, method in inspect.getmembers(interface, predicate=no_special_no_private):  # NOQA: ignore=E501
                 interface_methods[name] = method
             ##########
-            # python@2.7: interface_methods_dict = {name: IterateOver(name, method) for name, method in interface_methods.iteritems()}
+            # python@2.7: interface_methods_dict = {name: IterateOver(name,
+            # method) for name, method in interface_methods.iteritems()}
             interface_methods_dict = {}
             for name, method in interface_methods.iteritems():
                 interface_methods_dict[name] = IterateOver(name, method)
             ##########
             dictionary_for_type_call.update(interface_methods_dict)
-        # Get the methods that are defined in the scope of the composite class and override any previous definition
+        # Get the methods that are defined in the scope of the composite
+        # class and override any previous definition
         ##########
-        # python@2.7: cls_method = {name: method for name, method in inspect.getmembers(cls, predicate=inspect.ismethod)}
+        # python@2.7: cls_method = {name: method for name, method in
+        # inspect.getmembers(cls, predicate=inspect.ismethod)}
         cls_method = {}
-        for name, method in inspect.getmembers(cls, predicate=inspect.ismethod):
+        for name, method in inspect.getmembers(cls, predicate=inspect.ismethod):  # NOQA: ignore=E501
             cls_method[name] = method
         ##########
         dictionary_for_type_call.update(cls_method)
         # Generate the new class on the fly and return it
         # FIXME : inherit from interface if we start to use ABC classes?
-        wrapper_class = type(cls.__name__, (cls, container), dictionary_for_type_call)
+        wrapper_class = type(cls.__name__, (cls, container),
+                             dictionary_for_type_call)
         return wrapper_class
 
     return cls_decorator
+
+
+class Bunch(object):
+    """Carries a bunch of named attributes (from Alex Martelli bunch)"""
+
+    def __init__(self, **kwargs):
+        self.__dict__.update(kwargs)