solver setup: extract virtual dependencies from reusable specs (#32434)

* extract virtual dependencies from reusable specs
* bugfix to avoid establishing new node for virtual

lib/spack/spack/solver/asp.py

@@ -1463,6 +1463,12 @@ class Body(object):
                         if concrete_build_deps or dtype != "build":
                             clauses.append(fn.depends_on(spec.name, dep.name, dtype))
 
+                            # Ensure Spack will not coconcretize this with another provider
+                            # for the same virtual
+                            for virtual in dep.package.virtuals_provided:
+                                clauses.append(fn.virtual_node(virtual.name))
+                                clauses.append(fn.provider(dep.name, virtual.name))
+
                     # imposing hash constraints for all but pure build deps of
                     # already-installed concrete specs.
                     if concrete_build_deps or dspec.deptypes != ("build",):

lib/spack/spack/test/concretize.py

@@ -1706,6 +1706,28 @@ def test_best_effort_coconcretize_preferences(self, specs, expected_spec, occura
                 counter += 1
         assert counter == occurances, concrete_specs
 
+    def test_coconcretize_reuse_and_virtuals(self):
+        import spack.solver.asp
+
+        if spack.config.get("config:concretizer") == "original":
+            pytest.skip("Original concretizer cannot reuse")
+
+        reusable_specs = []
+        for s in ["mpileaks ^mpich", "zmpi"]:
+            reusable_specs.extend(spack.spec.Spec(s).concretized().traverse(root=True))
+
+        root_specs = [spack.spec.Spec("mpileaks"), spack.spec.Spec("zmpi")]
+
+        import spack.solver.asp
+
+        with spack.config.override("concretizer:reuse", True):
+            solver = spack.solver.asp.Solver()
+            setup = spack.solver.asp.SpackSolverSetup()
+            result, _, _ = solver.driver.solve(setup, root_specs, reuse=reusable_specs)
+
+        for spec in result.specs:
+            assert "zmpi" in spec
+
     @pytest.mark.regression("30864")
     def test_misleading_error_message_on_version(self, mutable_database):
         # For this bug to be triggered we need a reusable dependency