Fix assumption v.concrete => isinstance(v, Version) (#26537)

* Add test
* Only extend with Git version when using Version
* xfail v.concrete test

lib/spack/spack/spec.py

@@ -4754,8 +4754,12 @@ def do_parse(self):
         # Generate lookups for git-commit-based versions
         for spec in specs:
             # Cannot do lookups for versions in anonymous specs
-            # Only allow concrete versions using git for now
-            if spec.name and spec.versions.concrete and spec.version.is_commit:
+            # Only allow Version objects to use git for now
+            # Note: VersionRange(x, x) is currently concrete, hence isinstance(...).
+            if (
+                spec.name and spec.versions.concrete and
+                isinstance(spec.version, vn.Version) and spec.version.is_commit
+            ):
                 pkg = spec.package
                 if hasattr(pkg, 'git'):
                     spec.version.generate_commit_lookup(pkg)

lib/spack/spack/test/versions.py

@@ -628,3 +628,20 @@ def test_version_wrong_idx_type():
     v = Version('1.1')
     with pytest.raises(TypeError):
         v['0:']
+
+
+@pytest.mark.regression('26482')
+def test_version_list_with_range_included_in_concrete_version_interpreted_as_range():
+    # Note: this test only tests whether we can construct a version list of a range
+    # and a version, where the range is contained in the version when it is interpreted
+    # as a range. That is: Version('3.1') interpreted as VersionRange('3.1', '3.1').
+    # Cleary it *shouldn't* be interpreted that way, but that is how Spack currently
+    # behaves, and this test only ensures that creating a VersionList of this type
+    # does not throw like reported in the linked Github issue.
+    VersionList([Version('3.1'), VersionRange('3.1.1', '3.1.2')])
+
+
+@pytest.mark.xfail
+def test_version_list_with_range_and_concrete_version_is_not_concrete():
+    v = VersionList([Version('3.1'), VersionRange('3.1.1', '3.1.2')])
+    assert v.concrete