add test file for conditional dependencies

Signed-off-by: Gregory Becker <becker33@llnl.gov>

lib/spack/spack/test/concretization/conditional_dependencies.py

@@ -0,0 +1,67 @@
+# Copyright Spack Project Developers. See COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+import pytest
+
+import spack.concretize
+import spack.config
+import spack.spec
+
+
+@pytest.mark.parametrize("holds,mpi", [(True, "zmpi"), (True, "mpich"), (False, "mpich")])
+def test_conditional_deps(holds, mpi, config, mock_packages):
+    sigil = "+" if holds else "~"
+    request = f"hdf5{sigil}mpi ^[when='^mpi' virtuals=mpi]{mpi}"
+    concrete = spack.concretize.concretize_one(request)
+
+    assert (mpi in concrete) == holds
+    assert ("mpi" in concrete) == holds
+
+
+@pytest.mark.parametrize("c", [True, False])
+@pytest.mark.parametrize("cxx", [True, False])
+@pytest.mark.parametrize("fortran", [True, False])
+def test_conditional_compilers(c, cxx, fortran, mutable_config, mock_packages):
+    # Configure two gcc compilers that could be concretized to
+    # We will confirm concretization matches the less preferred one
+    extra_attributes_block = {
+        "compilers": {"c": "/path/to/gcc", "cxx": "/path/to/g++", "fortran": "/path/to/fortran"}
+    }
+    spack.config.CONFIG.set(
+        "packages:gcc:externals::",
+        [
+            {
+                "spec": "gcc@12.3.1 languages=c,c++,fortran",
+                "prefix": "/path",
+                "extra_attributes": extra_attributes_block,
+            },
+            {
+                "spec": "gcc@10.3.1 languages=c,c++,fortran",
+                "prefix": "/path",
+                "extra_attributes": extra_attributes_block,
+            },
+        ],
+    )
+
+    # Abstract spec parametrized to depend/not on c/cxx/fortran
+    # and with conditional dependencies for each on the less preferred gcc
+    abstract = spack.spec.Spec("conditional-languages")
+    abstract.constrain(f"c={c}")
+    abstract.constrain(f"cxx={cxx}")
+    abstract.constrain(f"fortran={fortran}")
+
+    preferred_gcc = spack.concretize.concretize_one(abstract)
+    abstract.constrain(
+        "^[when='%c' virtuals=c]gcc@10.3.1 "
+        "^[when='%cxx' virtuals=cxx]gcc@10.3.1 "
+        "^[when='%fortran' virtuals=fortran]gcc@10.3.1"
+    )
+    concrete = spack.concretize.concretize_one(abstract)
+
+    # We should get the dependency we specified for each language we enabled
+    assert concrete.satisfies("%[virtuals=c]gcc@10.3.1") == c
+    assert concrete.satisfies("%[virtuals=cxx]gcc@10.3.1") == cxx
+    assert concrete.satisfies("%[virtuals=fortran]gcc@10.3.1") == fortran
+
+    # The only time the two concrete specs are the same is if we don't use gcc at all
+    assert (concrete == preferred_gcc) == (not any((c, cxx, fortran)))