Feature: Allow lmod configuration to set core specs (#16517)

Packages built with lmod core_compiler are placed in `Core`.

Other packages may belong in `Core`. For example, python may be built with a proprietary compiler for performance, but belong on the `Core` directory.

With this PR, lmod config can include a `core_specs` list. Any package that satisfies a spec in that list is placed in `Core`, regardless of its compiler or dependencies.

lib/spack/docs/module_file_support.rst

@@ -538,6 +538,8 @@ most likely via the ``+blas`` variant specification.
          lmod:
            core_compilers:
              - 'gcc@4.8'
+           core_specs:
+             - 'python'
            hierarchy:
              - 'mpi'
              - 'lapack'
@@ -547,6 +549,15 @@ most likely via the ``+blas`` variant specification.
      implementations of ``mpi`` and ``lapack``, and let LMod switch safely from one to the
      other.
 
+     All packages built with a compiler in ``core_compilers`` and all
+     packages that satisfy a spec in ``core_specs`` will be put in the
+     ``Core`` hierarchy of the lua modules.
+
+.. warning::
+  Consistency of Core packages
+   The user is responsible for maintining consistency among core packages, as ``core_specs``
+   bypasses the hierarchy that allows LMod to safely switch between coherent software stacks.
+
 .. warning::
   Deep hierarchies and ``lmod spider``
    For hierarchies that are deeper than three layers ``lmod spider`` may have some issues.

lib/spack/spack/modules/lmod.py

@@ -110,6 +110,11 @@ def core_compilers(self):
             raise CoreCompilersNotFoundError(msg)
         return value
 
+    @property
+    def core_specs(self):
+        """Returns the list of "Core" specs"""
+        return configuration().get('core_specs', [])
+
     @property
     def hierarchy_tokens(self):
         """Returns the list of tokens that are part of the modulefile
@@ -140,6 +145,11 @@ def requires(self):
         to the actual provider. 'compiler' is always present among the
         requirements.
         """
+        # If it's a core_spec, lie and say it requires a core compiler
+        if any(self.spec.satisfies(core_spec)
+               for core_spec in self.core_specs):
+            return {'compiler': self.core_compilers[0]}
+
         # Keep track of the requirements that this package has in terms
         # of virtual packages that participate in the hierarchical structure
         requirements = {'compiler': self.spec.compiler}

lib/spack/spack/schema/modules.py

@@ -16,7 +16,7 @@
 #:
 #: THIS NEEDS TO BE UPDATED FOR EVERY NEW KEYWORD THAT
 #: IS ADDED IMMEDIATELY BELOW THE MODULE TYPE ATTRIBUTE
-spec_regex = r'(?!hierarchy|verbose|hash_length|whitelist|' \
+spec_regex = r'(?!hierarchy|core_specs|verbose|hash_length|whitelist|' \
              r'blacklist|naming_scheme|core_compilers|all)(^\w[\w-]*)'
 
 #: Matches an anonymous spec, i.e. a spec without a root name
@@ -145,7 +145,8 @@
                         'type': 'object',
                         'properties': {
                             'core_compilers': array_of_strings,
-                            'hierarchy': array_of_strings
+                            'hierarchy': array_of_strings,
+                            'core_specs': array_of_strings,
                         },
                     }  # Specific lmod extensions
                 ]

lib/spack/spack/test/data/modules/lmod/complex_hierarchy.yaml

@@ -6,6 +6,9 @@ lmod:
   core_compilers:
     - 'clang@3.3'
 
+  core_specs:
+    - 'mpich@3.0.1'
+
   hierarchy:
     - lapack
     - blas

lib/spack/spack/test/modules/lmod.py

@@ -27,6 +27,7 @@ def compiler(request):
 
 @pytest.fixture(params=[
     ('mpich@3.0.4', ('mpi',)),
+    ('mpich@3.0.1', []),
     ('openblas@0.2.15', ('blas',)),
     ('openblas-with-lapack@0.2.15', ('blas', 'lapack'))
 ])
@@ -54,7 +55,8 @@ def test_file_layout(
         # Check that the compiler part of the path has no hash and that it
         # is transformed to r"Core" if the compiler is listed among core
         # compilers
-        if compiler == 'clang@3.3':
+        # Check that specs listed as core_specs are transformed to "Core"
+        if compiler == 'clang@3.3' or spec_string == 'mpich@3.0.1':
             assert 'Core' in layout.available_path_parts
         else:
             assert compiler.replace('@', '/') in layout.available_path_parts