fix != version constraint incorrectly excluding pre/post/dev releases

Author: dimbleby

src/poetry/core/constraints/version/version_union.py

@@ -100,14 +100,7 @@ def has_upper_bound(self) -> bool:
 
     def allows(self, version: Version) -> bool:
         if self.excludes_single_version:
-            # when excluded version is local, special handling is required
-            # to ensure that a constraint (!=2.0+deadbeef) will allow the
-            # provided version (2.0)
-
-            excluded = self._excluded_single_version
-
-            if excluded.is_local():
-                return excluded != version
+            return not self._excluded_single_version.allows(version)
 
         return any(constraint.allows(version) for constraint in self._ranges)
 

tests/constraints/version/test_version_range.py

@@ -430,6 +430,14 @@ def test_union(
             ("2.0.1", "!=2.0"),
             ("2.0.1", "!=2.0.0"),
             ("2.0", "!=2.0+deadbeef"),
+            # != must not inherit exclusive ordered comparison rules from < and >
+            # (pre-releases, post-releases, dev-releases of the specified
+            # version are not equal to it)
+            ("2.0.dev1", "!=2"),
+            ("2.0a1", "!=2"),
+            ("2.0b1", "!=2"),
+            ("2.0rc1", "!=2"),
+            ("2.0.post1", "!=2"),
             # Test the in-equality operation with a prefix
             ("2.0", "!=3.*"),
             ("2.1", "!=2.0.*"),
@@ -581,25 +589,10 @@ def test_specifiers(version: str, spec: str, expected: bool) -> None:
     https://github.com/pypa/packaging/blob/8b86d85797b9f26d98ecfbe0271ce4dc9495d98c/tests/test_specifiers.py#L469
     """
     constraint = parse_constraint(spec)
-
     v = Version.parse(version)
 
-    if expected:
-        # Test that the plain string form works
-        # assert version in spec
-        assert constraint.allows(v)
-
-        # Test that the version instance form works
-        # assert version in spec
-        assert constraint.allows(v)
-    else:
-        # Test that the plain string form works
-        # assert version not in spec
-        assert not constraint.allows(v)
-
-        # Test that the version instance form works
-        # assert version not in spec
-        assert not constraint.allows(v)
+    allowed = constraint.allows(v)
+    assert allowed is expected
 
 
 @pytest.mark.parametrize(