provider index: removed import from + refactored a few parts (#15570)

Removed provider_index use of 'import from' and refactored a few routines to a further subclassing of _IndexBase for implementing user defined bindings of provider specs.

2 files changed, 179 insertions, 130 deletions

diff --git a/lib/spack/spack/provider_index.py b/lib/spack/spack/provider_index.py
index 9bf4af8911..326f6aa8f1 100644
--- a/lib/spack/spack/provider_index.py
+++ b/lib/spack/spack/provider_index.py
@@ -2,54 +2,147 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
+"""Classes and functions to manage providers of virtual dependencies"""
+import itertools
 
-"""
-The ``virtual`` module contains utility classes for virtual dependencies.
-"""
-
-from itertools import product as iproduct
-from six import iteritems
-from pprint import pformat
-
+import six
 import spack.error
 import spack.util.spack_json as sjson
 
 
-class ProviderIndex(object):
-    """This is a dict of dicts used for finding providers of particular
-       virtual dependencies. The dict of dicts looks like:
+def _cross_provider_maps(lmap, rmap):
+    """Return a dictionary that combines constraint requests from both input.
 
-       { vpkg name :
-           { full vpkg spec : set(packages providing spec) } }
+    Args:
+        lmap: main provider map
+        rmap: provider map with additional constraints
+    """
+    # TODO: this is pretty darned nasty, and inefficient, but there
+    # TODO: are not that many vdeps in most specs.
+    result = {}
+    for lspec, rspec in itertools.product(lmap, rmap):
+        try:
+            constrained = lspec.constrained(rspec)
+        except spack.error.UnsatisfiableSpecError:
+            continue
+
+        # lp and rp are left and right provider specs.
+        for lp_spec, rp_spec in itertools.product(lmap[lspec], rmap[rspec]):
+            if lp_spec.name == rp_spec.name:
+                try:
+                    const = lp_spec.constrained(rp_spec, deps=False)
+                    result.setdefault(constrained, set()).add(const)
+                except spack.error.UnsatisfiableSpecError:
+                    continue
+    return result
+
+
+class _IndexBase(object):
+    #: This is a dict of dicts used for finding providers of particular
+    #: virtual dependencies. The dict of dicts looks like:
+    #:
+    #:    { vpkg name :
+    #:        { full vpkg spec : set(packages providing spec) } }
+    #:
+    #: Callers can use this to first find which packages provide a vpkg,
+    #: then find a matching full spec.  e.g., in this scenario:
+    #:
+    #:    { 'mpi' :
+    #:        { mpi@:1.1 : set([mpich]),
+    #:          mpi@:2.3 : set([mpich2@1.9:]) } }
+    #:
+    #: Calling providers_for(spec) will find specs that provide a
+    #: matching implementation of MPI. Derived class need to construct
+    #: this attribute according to the semantics above.
+    providers = None
+
+    def providers_for(self, virtual_spec):
+        """Return a list of specs of all packages that provide virtual
+        packages with the supplied spec.
+
+        Args:
+            virtual_spec: virtual spec to be provided
+        """
+        result = set()
+        # Allow string names to be passed as input, as well as specs
+        if isinstance(virtual_spec, six.string_types):
+            virtual_spec = spack.spec.Spec(virtual_spec)
 
-       Callers can use this to first find which packages provide a vpkg,
-       then find a matching full spec.  e.g., in this scenario:
+        # Add all the providers that satisfy the vpkg spec.
+        if virtual_spec.name in self.providers:
+            for p_spec, spec_set in self.providers[virtual_spec.name].items():
+                if p_spec.satisfies(virtual_spec, deps=False):
+                    result.update(spec_set)
 
-       { 'mpi' :
-           { mpi@:1.1 : set([mpich]),
-             mpi@:2.3 : set([mpich2@1.9:]) } }
+        # Return providers in order. Defensively copy.
+        return sorted(s.copy() for s in result)
 
-       Calling providers_for(spec) will find specs that provide a
-       matching implementation of MPI.
+    def __contains__(self, name):
+        return name in self.providers
 
-    """
+    def satisfies(self, other):
+        """Determine if the providers of virtual specs are compatible.
 
-    def __init__(self, specs=None, restrict=False):
-        """Create a new ProviderIndex.
+        Args:
+            other: another provider index
+
+        Returns:
+            True if the providers are compatible, False otherwise.
+        """
+        common = set(self.providers) & set(other.providers)
+        if not common:
+            return True
+
+        # This ensures that some provider in other COULD satisfy the
+        # vpkg constraints on self.
+        result = {}
+        for name in common:
+            crossed = _cross_provider_maps(
+                self.providers[name], other.providers[name]
+            )
+            if crossed:
+                result[name] = crossed
+
+        return all(c in result for c in common)
+
+    def __eq__(self, other):
+        return self.providers == other.providers
 
-        Optional arguments:
+    def _transform(self, transform_fun, out_mapping_type=dict):
+        """Transform this provider index dictionary and return it.
+
+        Args:
+            transform_fun: transform_fun takes a (vpkg, pset) mapping and runs
+                it on each pair in nested dicts.
+            out_mapping_type: type to be used internally on the
+                transformed (vpkg, pset)
+
+        Returns:
+            Transformed mapping
+        """
+        return _transform(self.providers, transform_fun, out_mapping_type)
+
+    def __str__(self):
+        return str(self.providers)
 
-        specs
-            List (or sequence) of specs.  If provided, will call
-            `update` on this ProviderIndex with each spec in the list.
+    def __repr__(self):
+        return repr(self.providers)
 
-        restrict
-            "restricts" values to the verbatim input specs; do not
-            pre-apply package's constraints.
 
-            TODO: rename this.  It is intended to keep things as broad
-            as possible without overly restricting results, so it is
-            not the best name.
+class ProviderIndex(_IndexBase):
+    def __init__(self, specs=None, restrict=False):
+        """Provider index based on a single mapping of providers.
+
+        Args:
+            specs (list of specs): if provided, will call update on each
+                single spec to initialize this provider index.
+
+            restrict: "restricts" values to the verbatim input specs; do not
+                pre-apply package's constraints.
+
+        TODO: rename this.  It is intended to keep things as broad
+        TODO: as possible without overly restricting results, so it is
+        TODO: not the best name.
         """
         if specs is None:
             specs = []
@@ -67,6 +160,11 @@ class ProviderIndex(object):
             self.update(spec)
 
     def update(self, spec):
+        """Update the provider index with additional virtual specs.
+
+        Args:
+            spec: spec potentially providing additional virtual specs
+        """
         if not isinstance(spec, spack.spec.Spec):
             spec = spack.spec.Spec(spec)
 
@@ -74,10 +172,10 @@ class ProviderIndex(object):
             # Empty specs do not have a package
             return
 
-        assert(not spec.virtual)
+        assert not spec.virtual, "cannot update an index using a virtual spec"
 
         pkg_provided = spec.package_class.provided
-        for provided_spec, provider_specs in iteritems(pkg_provided):
+        for provided_spec, provider_specs in six.iteritems(pkg_provided):
             for provider_spec in provider_specs:
                 # TODO: fix this comment.
                 # We want satisfaction other than flags
@@ -110,94 +208,24 @@ class ProviderIndex(object):
                         constrained.constrain(provider_spec)
                         provider_map[provided_spec].add(constrained)
 
-    def providers_for(self, *vpkg_specs):
-        """Gives specs of all packages that provide virtual packages
-           with the supplied specs."""
-        providers = set()
-        for vspec in vpkg_specs:
-            # Allow string names to be passed as input, as well as specs
-            if type(vspec) == str:
-                vspec = spack.spec.Spec(vspec)
-
-            # Add all the providers that satisfy the vpkg spec.
-            if vspec.name in self.providers:
-                for p_spec, spec_set in self.providers[vspec.name].items():
-                    if p_spec.satisfies(vspec, deps=False):
-                        providers.update(spec_set)
-
-        # Return providers in order. Defensively copy.
-        return sorted(s.copy() for s in providers)
-
-    # TODO: this is pretty darned nasty, and inefficient, but there
-    # are not that many vdeps in most specs.
-    def _cross_provider_maps(self, lmap, rmap):
-        result = {}
-        for lspec, rspec in iproduct(lmap, rmap):
-            try:
-                constrained = lspec.constrained(rspec)
-            except spack.error.UnsatisfiableSpecError:
-                continue
-
-            # lp and rp are left and right provider specs.
-            for lp_spec, rp_spec in iproduct(lmap[lspec], rmap[rspec]):
-                if lp_spec.name == rp_spec.name:
-                    try:
-                        const = lp_spec.constrained(rp_spec, deps=False)
-                        result.setdefault(constrained, set()).add(const)
-                    except spack.error.UnsatisfiableSpecError:
-                        continue
-        return result
-
-    def __contains__(self, name):
-        """Whether a particular vpkg name is in the index."""
-        return name in self.providers
-
-    def satisfies(self, other):
-        """Check that providers of virtual specs are compatible."""
-        common = set(self.providers) & set(other.providers)
-        if not common:
-            return True
-
-        # This ensures that some provider in other COULD satisfy the
-        # vpkg constraints on self.
-        result = {}
-        for name in common:
-            crossed = self._cross_provider_maps(self.providers[name],
-                                                other.providers[name])
-            if crossed:
-                result[name] = crossed
-
-        return all(c in result for c in common)
-
     def to_json(self, stream=None):
+        """Dump a JSON representation of this object.
+
+        Args:
+            stream: stream where to dump
+        """
         provider_list = self._transform(
             lambda vpkg, pset: [
                 vpkg.to_node_dict(), [p.to_node_dict() for p in pset]], list)
 
         sjson.dump({'provider_index': {'providers': provider_list}}, stream)
 
-    @staticmethod
-    def from_json(stream):
-        data = sjson.load(stream)
-
-        if not isinstance(data, dict):
-            raise ProviderIndexError("JSON ProviderIndex data was not a dict.")
-
-        if 'provider_index' not in data:
-            raise ProviderIndexError(
-                "YAML ProviderIndex does not start with 'provider_index'")
-
-        index = ProviderIndex()
-        providers = data['provider_index']['providers']
-        index.providers = _transform(
-            providers,
-            lambda vpkg, plist: (
-                spack.spec.Spec.from_node_dict(vpkg),
-                set(spack.spec.Spec.from_node_dict(p) for p in plist)))
-        return index
-
     def merge(self, other):
-        """Merge `other` ProviderIndex into this one."""
+        """Merge another provider index into this one.
+
+        Args:
+            other (ProviderIndex): provider index to be merged
+        """
         other = other.copy()   # defensive copy.
 
         for pkg in other.providers:
@@ -236,40 +264,61 @@ class ProviderIndex(object):
             del self.providers[pkg]
 
     def copy(self):
-        """Deep copy of this ProviderIndex."""
+        """Return a deep copy of this index."""
         clone = ProviderIndex()
         clone.providers = self._transform(
             lambda vpkg, pset: (vpkg, set((p.copy() for p in pset))))
         return clone
 
-    def __eq__(self, other):
-        return self.providers == other.providers
+    @staticmethod
+    def from_json(stream):
+        """Construct a provider index from its JSON representation.
 
-    def _transform(self, transform_fun, out_mapping_type=dict):
-        return _transform(self.providers, transform_fun, out_mapping_type)
+        Args:
+            stream: stream where to read from the JSON data
+        """
+        data = sjson.load(stream)
 
-    def __str__(self):
-        return pformat(
-            _transform(self.providers,
-                       lambda k, v: (k, list(v))))
+        if not isinstance(data, dict):
+            raise ProviderIndexError("JSON ProviderIndex data was not a dict.")
+
+        if 'provider_index' not in data:
+            raise ProviderIndexError(
+                "YAML ProviderIndex does not start with 'provider_index'")
+
+        index = ProviderIndex()
+        providers = data['provider_index']['providers']
+        index.providers = _transform(
+            providers,
+            lambda vpkg, plist: (
+                spack.spec.Spec.from_node_dict(vpkg),
+                set(spack.spec.Spec.from_node_dict(p) for p in plist)))
+        return index
 
 
 def _transform(providers, transform_fun, out_mapping_type=dict):
     """Syntactic sugar for transforming a providers dict.
 
-    transform_fun takes a (vpkg, pset) mapping and runs it on each
-    pair in nested dicts.
+    Args:
+        providers: provider dictionary
+        transform_fun: transform_fun takes a (vpkg, pset) mapping and runs
+            it on each pair in nested dicts.
+        out_mapping_type: type to be used internally on the
+            transformed (vpkg, pset)
 
+    Returns:
+        Transformed mapping
     """
     def mapiter(mappings):
         if isinstance(mappings, dict):
-            return iteritems(mappings)
+            return six.iteritems(mappings)
         else:
             return iter(mappings)
 
     return dict(
-        (name, out_mapping_type([
-            transform_fun(vpkg, pset) for vpkg, pset in mapiter(mappings)]))
+        (name, out_mapping_type(
+            [transform_fun(vpkg, pset) for vpkg, pset in mapiter(mappings)]
+        ))
         for name, mappings in providers.items())
 
 
diff --git a/lib/spack/spack/test/spec_dag.py b/lib/spack/spack/test/spec_dag.py
index 419a39968e..25917f9424 100644
--- a/lib/spack/spack/test/spec_dag.py
+++ b/lib/spack/spack/test/spec_dag.py
@@ -189,7 +189,7 @@ def test_conditional_dep_with_user_constraints():
         assert ('y@3' in spec)
 
 
-@pytest.mark.usefixtures('mutable_mock_repo')
+@pytest.mark.usefixtures('mutable_mock_repo', 'config')
 class TestSpecDag(object):
 
     def test_conflicting_package_constraints(self, set_dependency):