Set module variables for all packages before running setup_dependent_package (#44327)

When a package is running `setup_dependent_package` on a parent, ensure
that module variables like `spack_cc` are available. This was often
true prior to this commit, but externals were an exception.

---------

Co-authored-by: John Parent <john.parent@kitware.com>

lib/spack/spack/build_environment.py

@@ -1003,7 +1003,6 @@ def set_all_package_py_globals(self):
         """Set the globals in modules of package.py files."""
         for dspec, flag in chain(self.external, self.nonexternal):
             pkg = dspec.package
-
             if self.should_set_package_py_globals & flag:
                 if self.context == Context.BUILD and self.needs_build_context & flag:
                     set_package_py_globals(pkg, context=Context.BUILD)
@@ -1011,6 +1010,12 @@ def set_all_package_py_globals(self):
                     # This includes runtime dependencies, also runtime deps of direct build deps.
                     set_package_py_globals(pkg, context=Context.RUN)
 
+        # Looping over the set of packages a second time
+        # ensures all globals are loaded into the module space prior to
+        # any package setup. This guarantees package setup methods have
+        # access to expected module level definitions such as "spack_cc"
+        for dspec, flag in chain(self.external, self.nonexternal):
+            pkg = dspec.package
             for spec in dspec.dependents():
                 # Note: some specs have dependents that are unreachable from the root, so avoid
                 # setting globals for those.

lib/spack/spack/test/build_environment.py

@@ -513,6 +513,30 @@ def test_setting_dtags_based_on_config(config_setting, expected_flag, config, mo
         assert dtags_to_add.value == expected_flag
 
 
+def test_module_globals_available_at_setup_dependent_time(
+    monkeypatch, mutable_config, mock_packages, working_env
+):
+    """Spack built package externaltest depends on an external package
+    externaltool. Externaltool's setup_dependent_package needs to be able to
+    access globals on the dependent"""
+
+    def setup_dependent_package(module, dependent_spec):
+        # Make sure set_package_py_globals was already called on
+        # dependents
+        # ninja is always set by the setup context and is not None
+        dependent_module = dependent_spec.package.module
+        assert hasattr(dependent_module, "ninja")
+        assert dependent_module.ninja is not None
+        dependent_spec.package.test_attr = True
+
+    externaltool = spack.spec.Spec("externaltest").concretized()
+    monkeypatch.setattr(
+        externaltool["externaltool"].package, "setup_dependent_package", setup_dependent_package
+    )
+    spack.build_environment.setup_package(externaltool.package, False)
+    assert externaltool.package.test_attr
+
+
 def test_build_jobs_sequential_is_sequential():
     assert (
         determine_number_of_jobs(