new directive: conflicts() (#3125)

* Add conflicts(<spec>) directive
* openblas: added conflicts for intel@16 refs #3119
* added brief docs and unit tests

4 files changed, 99 insertions, 1 deletions

diff --git a/lib/spack/docs/packaging_guide.rst b/lib/spack/docs/packaging_guide.rst
index 1a64c7db4a..18541179b2 100644
--- a/lib/spack/docs/packaging_guide.rst
+++ b/lib/spack/docs/packaging_guide.rst
@@ -1560,6 +1560,28 @@ Python's ``setup_dependent_environment`` method also sets up some
 other variables, creates a directory, and sets up the ``PYTHONPATH``
 so that dependent packages can find their dependencies at build time.
 
+.. _packaging_conflicts:
+
+---------
+Conflicts
+---------
+
+Sometimes packages have known bugs, or limitations, that would prevent them
+to build e.g. against other dependencies or with certain compilers. Spack
+makes it possible to express such constraints with the ``conflicts`` directive.
+
+Adding the following to a package:
+
+.. code-block:: python
+
+    conflicts('%intel', when='@1.2')
+
+we express the fact that the current package *cannot be built* with the Intel
+compiler when we are trying to install version "1.2". The ``when`` argument can
+be omitted, in which case the conflict will always be active.
+Conflicts are always evaluated after the concretization step has been performed,
+and if any match is found a detailed error message is shown to the user.
+
 .. _packaging_extensions:
 
 ----------
diff --git a/lib/spack/spack/directives.py b/lib/spack/spack/directives.py
index db280cb5fd..e2219d1f49 100644
--- a/lib/spack/spack/directives.py
+++ b/lib/spack/spack/directives.py
@@ -263,6 +263,33 @@ def _depends_on(pkg, spec, when=None, type=None):
         conditions[when_spec] = dep_spec
 
 
+@directive('conflicts')
+def conflicts(conflict_spec, when=None):
+    """Allows a package to define a conflict, i.e. a concretized configuration
+    that is known to be non-valid.
+
+    For example a package that is known not to be buildable with intel
+    compilers can declare:
+
+    conflicts('%intel')
+
+    To express the same constraint only when the 'foo' variant is activated:
+
+    conflicts('%intel', when='+foo')
+
+    :param conflict_spec: constraint defining the known conflict
+    :param when: optional constraint that triggers the conflict
+    """
+    def _execute(pkg):
+        # If when is not specified the conflict always holds
+        condition = pkg.name if when is None else when
+        when_spec = parse_anonymous_spec(condition, pkg.name)
+
+        when_spec_list = pkg.conflicts.setdefault(conflict_spec, [])
+        when_spec_list.append(when_spec)
+    return _execute
+
+
 @directive(('dependencies', 'dependency_types'))
 def depends_on(spec, when=None, type=None):
     """Creates a dict of deps with specs defining when they apply.
diff --git a/lib/spack/spack/spec.py b/lib/spack/spack/spec.py
index 095b04f837..b6089c7849 100644
--- a/lib/spack/spack/spec.py
+++ b/lib/spack/spack/spec.py
@@ -1707,6 +1707,18 @@ class Spec(object):
         # Mark everything in the spec as concrete, as well.
         self._mark_concrete()
 
+        # Now that the spec is concrete we should check if
+        # there are declared conflicts
+        matches = []
+        for x in self.traverse():
+            for conflict_spec, when_list in x.package.conflicts.items():
+                if x.satisfies(conflict_spec):
+                    for when_spec in when_list:
+                        if x.satisfies(when_spec):
+                            matches.append((x, conflict_spec, when_spec))
+        if matches:
+            raise ConflictsInSpecError(self, matches)
+
     def _mark_concrete(self, value=True):
         """Mark this spec and its dependencies as concrete.
 
@@ -3336,3 +3348,15 @@ class RedundantSpecError(SpecError):
             "Attempting to add %s to spec %s which is already concrete."
             " This is likely the result of adding to a spec specified by hash."
             % (addition, spec))
+
+
+class ConflictsInSpecError(SpecError, RuntimeError):
+    def __init__(self, spec, matches):
+        message = 'Conflicts in concretized spec "{0}"\n'.format(
+            spec.short_spec
+        )
+        long_message = 'List of matching conflicts:\n\n'
+        match_fmt = '{0}. "{1}" conflicts with "{2}" in spec "{3}"\n'
+        for idx, (s, c, w) in enumerate(matches):
+            long_message += match_fmt.format(idx + 1, c, w, s)
+        super(ConflictsInSpecError, self).__init__(message, long_message)
diff --git a/lib/spack/spack/test/concretize.py b/lib/spack/spack/test/concretize.py
index f4021a89ee..3b383584ce 100644
--- a/lib/spack/spack/test/concretize.py
+++ b/lib/spack/spack/test/concretize.py
@@ -26,7 +26,7 @@ import pytest
 import spack
 import spack.architecture
 from spack.concretize import find_spec
-from spack.spec import Spec, CompilerSpec
+from spack.spec import Spec, CompilerSpec, ConflictsInSpecError, SpecError
 from spack.version import ver
 
 
@@ -82,6 +82,10 @@ def check_concretize(abstract_spec):
         'mpileaks ^mpi', 'mpileaks ^mpi@:1.1', 'mpileaks ^mpi@2:',
         'mpileaks ^mpi@2.1', 'mpileaks ^mpi@2.2', 'mpileaks ^mpi@2.2',
         'mpileaks ^mpi@:1', 'mpileaks ^mpi@1.2:2'
+        # conflict not triggered
+        'conflict',
+        'conflict%clang~foo',
+        'conflict-parent%gcc'
     ]
 )
 def spec(request):
@@ -89,6 +93,19 @@ def spec(request):
     return request.param
 
 
+@pytest.fixture(
+    params=[
+        'conflict%clang',
+        'conflict%clang+foo',
+        'conflict-parent%clang',
+        'conflict-parent@0.9^conflict~foo'
+    ]
+)
+def conflict_spec(request):
+    """Spec to be concretized"""
+    return request.param
+
+
 @pytest.mark.usefixtures('config', 'builtin_mock')
 class TestConcretize(object):
     def test_concretize(self, spec):
@@ -372,3 +389,11 @@ class TestConcretize(object):
         s.concretize()
         assert s['mpileaks'].satisfies('%clang')
         assert s['dyninst'].satisfies('%gcc')
+
+    def test_conflicts_in_spec(self, conflict_spec):
+        # Check that an exception is raised an caught by the appropriate
+        # exception types.
+        for exc_type in (ConflictsInSpecError, RuntimeError, SpecError):
+            s = Spec(conflict_spec)
+            with pytest.raises(exc_type):
+                s.concretize()