Rework compiler configuration and simplify config.py logic.

- `spack compiler` subcommands now take an optional --scope argument.

- no more `remove_from_config` in `config.py` -- `update` just
  overwrites b/c it's easier to just call `get_config`, modify YAML
  structures directly, and then call `update`.

- Implemented `spack compiler remove`.

4 files changed, 124 insertions, 73 deletions

diff --git a/lib/spack/spack/cmd/compiler.py b/lib/spack/spack/cmd/compiler.py
index af1a22c9dd..a3860abf76 100644
--- a/lib/spack/spack/cmd/compiler.py
+++ b/lib/spack/spack/cmd/compiler.py
@@ -22,6 +22,7 @@
 # along with this program; if not, write to the Free Software Foundation,
 # Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ##############################################################################
+import sys
 import argparse
 
 import llnl.util.tty as tty
@@ -41,17 +42,26 @@ def setup_parser(subparser):
     sp = subparser.add_subparsers(
         metavar='SUBCOMMAND', dest='compiler_command')
 
-    update_parser = sp.add_parser(
-        'add', help='Add compilers to the Spack configuration.')
-    update_parser.add_argument('add_paths', nargs=argparse.REMAINDER)
+    add_parser = sp.add_parser('add', help='Add compilers to the Spack configuration.')
+    add_parser.add_argument('add_paths', nargs=argparse.REMAINDER)
+    add_parser.add_argument('--scope', choices=spack.config.config_scopes,
+                            help="Configuration scope to modify.")
 
-    remove_parser = sp.add_parser('remove', help='remove compiler')
-    remove_parser.add_argument('path')
+    remove_parser = sp.add_parser('remove', help='Remove compiler by spec.')
+    remove_parser.add_argument(
+        '-a', '--all', action='store_true', help='Remove ALL compilers that match spec.')
+    remove_parser.add_argument('compiler_spec')
+    remove_parser.add_argument('--scope', choices=spack.config.config_scopes,
+                               help="Configuration scope to modify.")
 
-    list_parser   = sp.add_parser('list', help='list available compilers')
+    list_parser = sp.add_parser('list', help='list available compilers')
+    list_parser.add_argument('--scope', choices=spack.config.config_scopes,
+                             help="Configuration scope to read from.")
 
-    info_parser   = sp.add_parser('info', help='Show compiler paths.')
+    info_parser = sp.add_parser('info', help='Show compiler paths.')
     info_parser.add_argument('compiler_spec')
+    info_parser.add_argument('--scope', choices=spack.config.config_scopes,
+                             help="Configuration scope to read from.")
 
 
 def compiler_add(args):
@@ -62,13 +72,13 @@ def compiler_add(args):
         paths = get_path('PATH')
 
     compilers = [c for c in spack.compilers.find_compilers(*args.add_paths)
-                 if c.spec not in spack.compilers.all_compilers()]
+                 if c.spec not in spack.compilers.all_compilers(scope=args.scope)]
 
     if compilers:
-        spack.compilers.add_compilers_to_config('user', compilers)
+        spack.compilers.add_compilers_to_config(compilers, scope=args.scope)
         n = len(compilers)
         s = 's' if n > 1 else ''
-        filename = spack.config.get_config_filename('user', 'compilers')
+        filename = spack.config.get_config_filename(args.scope, 'compilers')
         tty.msg("Added %d new compiler%s to %s" % (n, s, filename))
         colify(reversed(sorted(c.spec for c in compilers)), indent=4)
     else:
@@ -76,13 +86,26 @@ def compiler_add(args):
 
 
 def compiler_remove(args):
-    pass
+    cspec = CompilerSpec(args.compiler_spec)
+    compilers = spack.compilers.compilers_for_spec(cspec, scope=args.scope)
+
+    if not compilers:
+        tty.die("No compilers match spec %s." % cspec)
+    elif not args.all and len(compilers) > 1:
+        tty.error("Multiple compilers match spec %s. Choose one:" % cspec)
+        colify(reversed(sorted([c.spec for c in compilers])), indent=4)
+        tty.msg("Or, you can use `spack compiler remove -a` to remove all of them.")
+        sys.exit(1)
+
+    for compiler in compilers:
+        spack.compilers.remove_compiler_from_config(compiler.spec, scope=args.scope)
+        tty.msg("Removed compiler %s." % compiler.spec)
 
 
 def compiler_info(args):
     """Print info about all compilers matching a spec."""
     cspec = CompilerSpec(args.compiler_spec)
-    compilers = spack.compilers.compilers_for_spec(cspec)
+    compilers = spack.compilers.compilers_for_spec(cspec, scope=args.scope)
 
     if not compilers:
         tty.error("No compilers match spec %s." % cspec)
@@ -97,7 +120,7 @@ def compiler_info(args):
 
 def compiler_list(args):
     tty.msg("Available compilers")
-    index = index_by(spack.compilers.all_compilers(), 'name')
+    index = index_by(spack.compilers.all_compilers(scope=args.scope), 'name')
     for i, (name, compilers) in enumerate(index.items()):
         if i >= 1: print
 
diff --git a/lib/spack/spack/cmd/compilers.py b/lib/spack/spack/cmd/compilers.py
index c485a910eb..7e09016f2d 100644
--- a/lib/spack/spack/cmd/compilers.py
+++ b/lib/spack/spack/cmd/compilers.py
@@ -26,9 +26,14 @@ import llnl.util.tty as tty
 from llnl.util.tty.colify import colify
 from llnl.util.lang import index_by
 
+import spack
 from spack.cmd.compiler import compiler_list
 
 description = "List available compilers. Same as 'spack compiler list'."
 
+def setup_parser(subparser):
+    subparser.add_argument('--scope', choices=spack.config.config_scopes,
+                           help="Configuration scope to read/modify.")
+
 def compilers(parser, args):
     compiler_list(args)
diff --git a/lib/spack/spack/compilers/__init__.py b/lib/spack/spack/compilers/__init__.py
index a1b6d978df..67dfaa3ac9 100644
--- a/lib/spack/spack/compilers/__init__.py
+++ b/lib/spack/spack/compilers/__init__.py
@@ -49,10 +49,10 @@ _required_instance_vars = ['cc', 'cxx', 'f77', 'fc']
 _default_order = ['gcc', 'intel', 'pgi', 'clang', 'xlc']
 
 def _auto_compiler_spec(function):
-    def converter(cspec_like):
+    def converter(cspec_like, *args, **kwargs):
         if not isinstance(cspec_like, spack.spec.CompilerSpec):
             cspec_like = spack.spec.CompilerSpec(cspec_like)
-        return function(cspec_like)
+        return function(cspec_like, *args, **kwargs)
     return converter
 
 
@@ -65,39 +65,87 @@ def _to_dict(compiler):
     }
 
 
-def get_compiler_config(arch=None):
+def get_compiler_config(arch=None, scope=None):
     """Return the compiler configuration for the specified architecture.
-
-       If the compiler configuration designates some compilers for
-       'all' architectures, those are merged into the result, as well.
-
     """
     # If any configuration file has compilers, just stick with the
     # ones already configured.
-    config = spack.config.get_config('compilers')
+    config = spack.config.get_config('compilers', scope=scope)
 
+    my_arch = spack.architecture.sys_type()
     if arch is None:
-        arch = spack.architecture.sys_type()
+        arch = my_arch
 
-    if arch not in config:
+    if arch in config:
+        return config[arch]
+
+    # Only for the current arch in *highest* scope: automatically try to
+    # find compilers if none are configured yet.
+    if arch == my_arch and scope == 'user':
         config[arch] = {}
         compilers = find_compilers(*get_path('PATH'))
         for compiler in compilers:
             config[arch].update(_to_dict(compiler))
-        spack.config.update_config('compilers', config)
+        spack.config.update_config('compilers', config, scope=scope)
+        return config[arch]
 
-    # Merge 'all' compilers with arch-specific ones.
-    merged_config = config.get('all', {})
-    merged_config = spack.config._merge_yaml(merged_config, config[arch])
+    return {}
+
+
+def add_compilers_to_config(compilers, arch=None, scope=None):
+    """Add compilers to the config for the specified architecture.
+
+    Arguments:
+      - compilers: a list of Compiler objects.
+      - arch:      arch to add compilers for.
+      - scope:     configuration scope to modify.
+    """
+    if arch is None:
+        arch = spack.architecture.sys_type()
+
+    compiler_config = get_compiler_config(arch, scope)
+    for compiler in compilers:
+        compiler_config[str(compiler.spec)] = dict(
+            (c, getattr(compiler, c, "None"))
+            for c in _required_instance_vars)
 
-    return merged_config
+    update = { arch : compiler_config }
+    spack.config.update_config('compilers', update, scope)
 
 
-def all_compilers(arch=None):
+@_auto_compiler_spec
+def remove_compiler_from_config(compiler_spec, arch=None, scope=None):
+    """Remove compilers from the config, by spec.
+
+    Arguments:
+      - compiler_specs: a list of CompilerSpec objects.
+      - arch:           arch to add compilers for.
+      - scope:          configuration scope to modify.
+    """
+    if arch is None:
+        arch = spack.architecture.sys_type()
+
+    compiler_config = get_compiler_config(arch, scope)
+    del compiler_config[str(compiler_spec)]
+    update = { arch : compiler_config }
+
+    spack.config.update_config('compilers', update, scope)
+
+
+def all_compilers(arch=None, scope=None):
     """Return a set of specs for all the compiler versions currently
        available to build with.  These are instances of CompilerSpec.
     """
-    return [spack.spec.CompilerSpec(s) for s in get_compiler_config(arch)]
+    # Get compilers for this architecture.
+    arch_config = get_compiler_config(arch, scope)
+
+    # Merge 'all' compilers with arch-specific ones.
+    # Arch-specific compilers have higher precedence.
+    merged_config = get_compiler_config('all', scope=scope)
+    merged_config = spack.config._merge_yaml(merged_config, arch_config)
+
+    # Return compiler specs for the result.
+    return [spack.spec.CompilerSpec(s) for s in merged_config]
 
 
 _cached_default_compiler = None
@@ -165,18 +213,18 @@ def supported(compiler_spec):
 
 
 @_auto_compiler_spec
-def find(compiler_spec):
+def find(compiler_spec, arch=None, scope=None):
     """Return specs of available compilers that match the supplied
        compiler spec.  Return an list if nothing found."""
-    return [c for c in all_compilers() if c.satisfies(compiler_spec)]
+    return [c for c in all_compilers(arch, scope) if c.satisfies(compiler_spec)]
 
 
 @_auto_compiler_spec
-def compilers_for_spec(compiler_spec):
+def compilers_for_spec(compiler_spec, arch=None, scope=None):
     """This gets all compilers that satisfy the supplied CompilerSpec.
        Returns an empty list if none are found.
     """
-    config = get_compiler_config()
+    config = get_compiler_config(arch, scope)
 
     def get_compiler(cspec):
         items = config[str(cspec)]
@@ -195,7 +243,7 @@ def compilers_for_spec(compiler_spec):
 
         return cls(cspec, *compiler_paths)
 
-    matches = find(compiler_spec)
+    matches = find(compiler_spec, arch, scope)
     return [get_compiler(cspec) for cspec in matches]
 
 
diff --git a/lib/spack/spack/config.py b/lib/spack/spack/config.py
index 9e3b44085f..d266d2e23f 100644
--- a/lib/spack/spack/config.py
+++ b/lib/spack/spack/config.py
@@ -311,7 +311,7 @@ def substitute_spack_prefix(path):
     return path.replace('$spack', spack.prefix)
 
 
-def get_config(section):
+def get_config(section, scope=None):
     """Get configuration settings for a section.
 
        Strips off the top-level section name from the YAML dict.
@@ -319,7 +319,12 @@ def get_config(section):
     validate_section(section)
     merged_section = {}
 
-    for scope in config_scopes.values():
+    if scope is None:
+        scopes = config_scopes.values()
+    else:
+        scopes = [validate_scope(scope)]
+
+    for scope in scopes:
         # read potentially cached data from the scope.
         data = scope.get_section(section)
         if not data or not section in data:
@@ -362,52 +367,22 @@ def get_config_filename(scope, section):
 def update_config(section, update_data, scope=None):
     """Update the configuration file for a particular scope.
 
-       Merges contents of update_data into the scope's data for the
-       specified section, then writes out the config file.
+       Overwrites contents of a section in a scope with update_data,
+       then writes out the config file.
 
-       update_data shoudl contain only the section's data, with the
-       top-level name stripped off.  This can be a list, dict, or any
+       update_data should have the top-level section name stripped off
+       (it will be re-added).  Data itself can be a list, dict, or any
        other yaml-ish structure.
 
     """
     # read in the config to ensure we've got current data
     get_config(section)
 
-    validate_section(section)     # validate section name
+    validate_section(section)       # validate section name
     scope = validate_scope(scope)   # get ConfigScope object from string.
 
     # read only the requested section's data.
-    data = scope.get_section(section)
-    data = _merge_yaml(data, { section : update_data })
-    scope.write_section(section)
-
-
-def remove_from_config(section, key_to_rm, scope=None):
-    """Remove a configuration key and write updated configuration to disk.
-
-       Return True if something was removed, False otherwise.
-
-    """
-    # ensure configs are current by reading in.
-    get_config(section)
-
-    # check args and get the objects we need.
-    scope = validate_scope(scope)
-    data = scope.get_section(section)
-    filename = scope.get_section_filename(section)
-
-    # do some checks
-    if not data:
-        return False
-
-    if not section in data:
-        raise ConfigFileError("Invalid configuration file: '%s'" % filename)
-
-    if key_to_rm not in section[section]:
-        return False
-
-    # remove the key from the section's configuration
-    del data[section][key_to_rm]
+    scope.sections[section] = { section : update_data }
     scope.write_section(section)