Fix Marker non-version-to-version comparison throwing InvalidVersion

src/packaging/markers.py

@@ -15,6 +15,7 @@
 from ._tokenizer import ParserSyntaxError
 from .specifiers import InvalidSpecifier, Specifier
 from .utils import canonicalize_name
+from .version import InvalidVersion, Version
 
 __all__ = [
     "EvaluateContext",
@@ -179,12 +180,20 @@ def _format_marker(
 
 def _eval_op(lhs: str, op: Op, rhs: str | AbstractSet[str]) -> bool:
     if isinstance(rhs, str):
+        # PEP 508 - Environment Markers
+        # https://peps.python.org/pep-0508/#environment-markers
+        # > The <version_cmp> operators use the PEP 440 version comparison rules
+        # > when those are defined (that is when both sides have a valid version
+        # > specifier). If there is no defined PEP 440 behaviour and the operator
+        # > exists in Python, then the operator falls back to the Python behaviour.
+        # > Otherwise an error should be raised.
         try:
             spec = Specifier("".join([op.serialize(), rhs]))
-        except InvalidSpecifier:
+            lhs_ver = Version(lhs)
+        except (InvalidSpecifier, InvalidVersion):
             pass
         else:
-            return spec.contains(lhs, prereleases=True)
+            return spec.contains(lhs_ver, prereleases=True)
 
     oper: Operator | None = _operators.get(op.serialize())
     if oper is None:

tests/test_markers.py

@@ -314,6 +314,23 @@ def test_environment_with_extra_none(self):
                 {"extra": "different__punctuation_is_EQUAL"},
                 True,
             ),
+            # extra name that is also a valid version - version comparison applies
+            # if both sides are valid versions
+            ("extra == 'v8'", {"extra": "quux"}, False),
+            ("extra == 'v8'", {"extra": "v8"}, True),
+            # LHS and RHS are valid versions, so equality uses normalized version
+            ("extra == 'v8-dev'", {"extra": "v8-dev.0"}, True),
+            # LHS and RHS are not valid versions, so equality is str comparison
+            ("extra == 'v8-foo'", {"extra": "v8-foo.0"}, False),
+            #
+            # When using order comparisons, fallback to str when one or both are
+            # not valid versions can have counter-intuitive results.
+            #
+            # The gentoo value is not a valid version, lexicographic str
+            # comparison applies. This is True because '6' >= '2'.
+            ("platform_release >= '20'", {"platform_release": "6.7.0-gentoo"}, True),
+            # Whereas this is False because the gentoo value IS a valid version
+            ("platform_release >= '20'", {"platform_release": "6.7.0+gentoo"}, False),
         ],
     )
     def test_evaluates(self, marker_string, environment, expected):