fix extendee_spec for transitive dependencies on potential extendees (#48025)

* fix extendee_spec for transitive dependencies on potential extendees

* regression test

* resolve conditional extensions on direct deps

* remove outdated comment

Co-authored-by: Harmen Stoppels <me@harmenstoppels.nl>

---------

Co-authored-by: Harmen Stoppels <me@harmenstoppels.nl>

lib/spack/spack/directives.py

@@ -462,8 +462,7 @@ def _execute_extends(pkg):
         if dep_spec.name == "python" and not pkg.name == "python-venv":
             _depends_on(pkg, spack.spec.Spec("python-venv"), when=when, type=("build", "run"))
 
-        # TODO: the values of the extendees dictionary are not used. Remove in next refactor.
-        pkg.extendees[dep_spec.name] = (dep_spec, None)
+        pkg.extendees[dep_spec.name] = (dep_spec, when_spec)
 
     return _execute_extends
 

lib/spack/spack/package_base.py

@@ -1288,12 +1288,13 @@ def extendee_spec(self):
         if not self.extendees:
             return None
 
-        deps = []
-
         # If the extendee is in the spec's deps already, return that.
-        for dep in self.spec.traverse(deptype=("link", "run")):
-            if dep.name in self.extendees:
-                deps.append(dep)
+        deps = [
+            dep
+            for dep in self.spec.dependencies(deptype=("link", "run"))
+            for d, when in self.extendees.values()
+            if dep.satisfies(d) and self.spec.satisfies(when)
+        ]
 
         if deps:
             assert len(deps) == 1

lib/spack/spack/test/directives.py

@@ -67,6 +67,20 @@ def test_extends_spec(config, mock_packages):
     assert extender.package.extends(extendee)
 
 
+@pytest.mark.regression("48024")
+def test_conditionally_extends_transitive_dep(config, mock_packages):
+    spec = spack.spec.Spec("conditionally-extends-transitive-dep").concretized()
+
+    assert not spec.package.extendee_spec
+
+
+@pytest.mark.regression("48025")
+def test_conditionally_extends_direct_dep(config, mock_packages):
+    spec = spack.spec.Spec("conditionally-extends-direct-dep").concretized()
+
+    assert not spec.package.extendee_spec
+
+
 @pytest.mark.regression("34368")
 def test_error_on_anonymous_dependency(config, mock_packages):
     pkg = spack.repo.PATH.get_pkg_class("pkg-a")