package: make possible_dependencies consider deptypes

- `PackageBase.possible_dependencies` now:
  - accepts a deptype param that controls dependency types traversed
  - returns a dict mapping possible depnames to their immediate possible
    dependencies (this lets you build a graph easily)

- Add tests for PackageBaes

3 files changed, 93 insertions, 16 deletions

diff --git a/lib/spack/spack/dependency.py b/lib/spack/spack/dependency.py
index b8fb1771de..3e427196b5 100644
--- a/lib/spack/spack/dependency.py
+++ b/lib/spack/spack/dependency.py
@@ -34,17 +34,14 @@ def canonical_deptype(deptype):
             raise ValueError('Invalid dependency type: %s' % deptype)
         return (deptype,)
 
-    elif isinstance(deptype, (tuple, list)):
+    elif isinstance(deptype, (tuple, list, set)):
         bad = [d for d in deptype if d not in all_deptypes]
         if bad:
             raise ValueError(
                 'Invalid dependency types: %s' % ','.join(str(t) for t in bad))
         return tuple(sorted(deptype))
 
-    elif deptype is None:
-        raise ValueError('Invalid dependency type: None')
-
-    return deptype
+    raise ValueError('Invalid dependency type: %s' % repr(deptype))
 
 
 class Dependency(object):
diff --git a/lib/spack/spack/package.py b/lib/spack/spack/package.py
index 99dfa0be1c..226e0d1643 100644
--- a/lib/spack/spack/package.py
+++ b/lib/spack/spack/package.py
@@ -35,6 +35,7 @@ import spack.paths
 import spack.store
 import spack.compilers
 import spack.directives
+import spack.dependency
 import spack.directory_layout
 import spack.error
 import spack.fetch_strategy as fs
@@ -530,39 +531,66 @@ class PackageBase(with_metaclass(PackageMeta, PackageViewMixin, object)):
 
     @classmethod
     def possible_dependencies(
-            cls, transitive=True, expand_virtuals=True, visited=None):
-        """Return set of possible transitive dependencies of this package.
-
-        Note: the set returned *includes* the package itself.
+            cls, transitive=True, expand_virtuals=True, deptype='all',
+            visited=None):
+        """Return dict of possible dependencies of this package.
 
         Args:
             transitive (bool): return all transitive dependencies if True,
                 only direct dependencies if False.
             expand_virtuals (bool): expand virtual dependencies into all
                 possible implementations.
+            deptype (str or tuple): dependency types to consider
             visited (set): set of names of dependencies visited so far.
+
+        Returns:
+            (dict): dictionary mapping dependency names to *their*
+                immediate dependencies
+
+        Each item in the returned dictionary maps a (potentially
+        transitive) dependency of this package to its possible
+        *immediate* dependencies. If ``expand_virtuals`` is ``False``,
+        virtual package names wil be inserted as keys mapped to empty
+        sets of dependencies.  Virtuals, if not expanded, are treated as
+        though they have no immediate dependencies
+
+        Note: the returned dict *includes* the package itself.
+
         """
+        deptype = spack.dependency.canonical_deptype(deptype)
+
         if visited is None:
-            visited = set([cls.name])
+            visited = {cls.name: set()}
 
-        for i, name in enumerate(cls.dependencies):
+        for name, conditions in cls.dependencies.items():
+            # check whether this dependency could be of the type asked for
+            types = [dep.type for cond, dep in conditions.items()]
+            types = set.union(*types)
+            if not any(d in types for d in deptype):
+                continue
+
+            # expand virtuals if enabled, otherwise just stop at virtuals
             if spack.repo.path.is_virtual(name):
                 if expand_virtuals:
                     providers = spack.repo.path.providers_for(name)
                     dep_names = [spec.name for spec in providers]
                 else:
-                    visited.add(name)
+                    visited.setdefault(name, set())
                     continue
             else:
                 dep_names = [name]
 
+            # add the dependency names to the visited dict
+            visited.setdefault(cls.name, set()).update(set(dep_names))
+
+            # recursively traverse dependencies
             for dep_name in dep_names:
                 if dep_name not in visited:
-                    visited.add(dep_name)
+                    visited.setdefault(dep_name, set())
                     if transitive:
-                        pkg = spack.repo.get(dep_name)
-                        pkg.possible_dependencies(
-                            transitive, expand_virtuals, visited)
+                        dep_cls = spack.repo.path.get_pkg_class(dep_name)
+                        dep_cls.possible_dependencies(
+                            transitive, expand_virtuals, deptype, visited)
 
         return visited
 
diff --git a/lib/spack/spack/test/package_class.py b/lib/spack/spack/test/package_class.py
new file mode 100644
index 0000000000..7ae5c64ec7
--- /dev/null
+++ b/lib/spack/spack/test/package_class.py
@@ -0,0 +1,52 @@
+# Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+"""Test class methods on Package objects.
+
+This doesn't include methods on package *instances* (like do_install(),
+etc.).  Only methods like ``possible_dependencies()`` that deal with the
+static DSL metadata for packages.
+"""
+
+import spack.repo
+
+
+def test_possible_dependencies(mock_packages):
+    mpileaks = spack.repo.get('mpileaks')
+    mpi_names = [spec.name for spec in spack.repo.path.providers_for('mpi')]
+
+    assert mpileaks.possible_dependencies() == {
+        'callpath': set(['dyninst'] + mpi_names),
+        'dyninst': set(['libdwarf', 'libelf']),
+        'fake': set(),
+        'libdwarf': set(['libelf']),
+        'libelf': set(),
+        'mpich': set(),
+        'mpich2': set(),
+        'mpileaks': set(['callpath'] + mpi_names),
+        'multi-provider-mpi': set(),
+        'zmpi': set(['fake']),
+    }
+
+
+def test_possible_dependencies_with_deptypes(mock_packages):
+    dtbuild1 = spack.repo.get('dtbuild1')
+
+    assert dtbuild1.possible_dependencies(deptype=('link', 'run')) == {
+        'dtbuild1': set(['dtrun2', 'dtlink2']),
+        'dtlink2': set(),
+        'dtrun2': set(),
+    }
+
+    assert dtbuild1.possible_dependencies(deptype=('build')) == {
+        'dtbuild1': set(['dtbuild2', 'dtlink2']),
+        'dtbuild2': set(),
+        'dtlink2': set(),
+    }
+
+    assert dtbuild1.possible_dependencies(deptype=('link')) == {
+        'dtbuild1': set(['dtlink2']),
+        'dtlink2': set(),
+    }