Fix a bug when a required provider is requested for multiple virtuals (#42088)

3 files changed, 39 insertions, 3 deletions

diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index bc9a3e2fd7..7df2e0ff8a 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -1747,9 +1747,10 @@ class SpackSolverSetup:
             rules = self._rules_from_requirements(
                 virtual_str, requirements, kind=RequirementKind.VIRTUAL
             )
-            self.emit_facts_from_requirement_rules(rules)
-            self.trigger_rules()
-            self.effect_rules()
+            if rules:
+                self.emit_facts_from_requirement_rules(rules)
+                self.trigger_rules()
+                self.effect_rules()
 
     def emit_facts_from_requirement_rules(self, rules: List[RequirementRule]):
         """Generate facts to enforce requirements.
diff --git a/lib/spack/spack/solver/concretize.lp b/lib/spack/spack/solver/concretize.lp
index c56f2bcc66..c8d96eed9c 100644
--- a/lib/spack/spack/solver/concretize.lp
+++ b/lib/spack/spack/solver/concretize.lp
@@ -698,6 +698,18 @@ requirement_group_satisfied(node(ID, Package), X) :-
   activate_requirement(node(ID, Package), X),
   requirement_group(Package, X).
 
+% When we have a required provider, we need to ensure that the provider/2 facts respect
+% the requirement. This is particularly important for packages that could provide multiple
+% virtuals independently
+required_provider(Provider, Virtual)
+  :- requirement_group_member(ConditionID, Virtual, RequirementID),
+     condition_holds(ConditionID, _),
+     virtual(Virtual),
+     pkg_fact(Virtual, condition_effect(ConditionID, EffectID)),
+     imposed_constraint(EffectID, "node", Provider).
+
+:- provider(node(Y, Package), node(X, Virtual)), required_provider(Provider, Virtual), Package != Provider.
+
 % TODO: the following two choice rules allow the solver to add compiler
 % flags if their only source is from a requirement. This is overly-specific
 % and should use a more-generic approach like in https://github.com/spack/spack/pull/37180
diff --git a/lib/spack/spack/test/concretize_requirements.py b/lib/spack/spack/test/concretize_requirements.py
index 7b8f825eae..3a6b2b75c4 100644
--- a/lib/spack/spack/test/concretize_requirements.py
+++ b/lib/spack/spack/test/concretize_requirements.py
@@ -1012,3 +1012,26 @@ def test_default_requirements_semantic_with_mv_variants(
 
     for constraint in not_expected:
         assert not s.satisfies(constraint), constraint
+
+
+@pytest.mark.regression("42084")
+def test_requiring_package_on_multiple_virtuals(concretize_scope, mock_packages):
+    update_packages_config(
+        """
+    packages:
+      all:
+        providers:
+          scalapack: [netlib-scalapack]
+      blas:
+        require: intel-parallel-studio
+      lapack:
+        require: intel-parallel-studio
+      scalapack:
+        require: intel-parallel-studio
+    """
+    )
+    s = Spec("dla-future").concretized()
+
+    assert s["blas"].name == "intel-parallel-studio"
+    assert s["lapack"].name == "intel-parallel-studio"
+    assert s["scalapack"].name == "intel-parallel-studio"