Fix union(range, public_version) to fill local-variant punctures

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

@@ -109,28 +109,16 @@ def intersect(self, other: VersionConstraint) -> VersionConstraint:
         return other.intersect(self)
 
     def union(self, other: VersionConstraint) -> VersionConstraint:
-        from poetry.core.constraints.version.version_range import VersionRange
+        if not isinstance(other, Version):
+            # Delegate to the other operand's ``union`` so the broadening
+            # rules for local-tagged bounds are applied symmetrically
+            # whether the union is written as ``range.union(point)`` or
+            # ``point.union(range)``.
+            return other.union(self)
 
         if other.allows(self):
             return other
 
-        if isinstance(other, VersionRangeConstraint):
-            if self.allows(other.min):
-                return VersionRange(
-                    other.min,
-                    other.max,
-                    include_min=True,
-                    include_max=other.include_max,
-                )
-
-            if self.allows(other.max):
-                return VersionRange(
-                    other.min,
-                    other.max,
-                    include_min=other.include_min,
-                    include_max=True,
-                )
-
         return VersionUnion.of(self, other)
 
     def difference(self, other: VersionConstraint) -> Version | EmptyConstraint:

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

@@ -215,6 +215,9 @@ def intersect(self, other: VersionConstraint) -> VersionConstraint:
                 and not other.is_local()
                 and other.allows(self.min)
             ):
+                # Strictly speaking, next_patch() is not quite correct
+                # because you cannot specify the upper bound. It only
+                # works for versions with a precision of three or less.
                 upper = other.stable.next_patch()
                 return _range_or_empty(
                     min=self.min,
@@ -269,6 +272,42 @@ def union(self, other: VersionConstraint) -> VersionConstraint:
         from poetry.core.constraints.version.version import Version
 
         if isinstance(other, Version):
+            # If ``other`` is a public version that covers any local-tagged
+            # variants at our bounds (by PEP 440 release-equality), the
+            # union absorbs those local variants and we can broaden the
+            # bound(s).  Handle both bounds at once so e.g. a range that is
+            # bracketed by two local variants of ``other`` collapses to a
+            # single release-spanning range.
+            new_min: Version | None = self._min
+            new_include_min = self._include_min
+            new_max: Version | None = self._max
+            new_include_max = self._include_max
+            broadened = False
+            if not other.is_local():
+                if (
+                    self._min is not None
+                    and self._min.is_local()
+                    and other.allows(self._min)
+                ):
+                    new_min = other
+                    new_include_min = True
+                    broadened = True
+                if (
+                    self._max is not None
+                    and self._max.is_local()
+                    and other.allows(self._max)
+                ):
+                    # Strictly speaking, next_patch() is not quite correct
+                    # because you cannot specify the upper bound. It only
+                    # works for versions with a precision of three or less.
+                    new_max = other.stable.next_patch()
+                    new_include_max = False
+                    broadened = True
+            if broadened:
+                return _range_or_empty(
+                    new_min, new_max, new_include_min, new_include_max
+                )
+
             if self.allows(other):
                 return self
 

tests/constraints/version/test_version_range.py

@@ -812,6 +812,104 @@ def test_intersect_punctured_range_with_excluded_point_is_empty() -> None:
     assert excluded_point.intersect(punctured).is_empty()
 
 
+def test_union_upper_bound_local_with_public_extends_to_next_patch() -> None:
+    """``>=X,<X+local union ==X`` broadens the upper bound to
+    ``X.next_patch()`` (exclusive). ``==X`` matches every ``X+local``
+    variant by PEP 440 release-equality, so the union must cover them.
+    """
+    range_below = VersionRange(
+        Version.parse("0.21.0"),
+        Version.parse("0.21.0+cpu"),
+        include_min=True,
+        include_max=False,
+    )
+    public = Version.parse("0.21.0")
+    expected = VersionRange(
+        Version.parse("0.21.0"),
+        Version.parse("0.21.1"),
+        include_min=True,
+        include_max=False,
+    )
+    assert range_below.union(public) == expected
+    assert public.union(range_below) == expected
+
+
+def test_union_local_bounds_with_public_collapses_to_next_patch() -> None:
+    """``>=X+local1,<=X+local2 union ==X`` collapses to ``[X, X.next_patch())``.
+    Both bounds are local variants of the same public version ``X``.
+    Since ``==X`` matches all of them by PEP 440 release-equality, the
+    union must cover the entire public range up to ``X.next_patch()``.
+    """
+    range_locals = VersionRange(
+        Version.parse("0.21.0+cpu"),
+        Version.parse("0.21.0+gpu"),
+        include_min=True,
+        include_max=True,
+    )
+    public = Version.parse("0.21.0")
+    expected = VersionRange(
+        Version.parse("0.21.0"),
+        Version.parse("0.21.1"),
+        include_min=True,
+        include_max=False,
+    )
+    assert range_locals.union(public) == expected
+    assert public.union(range_locals) == expected
+
+
+def test_union_lower_bound_local_with_public_extends_to_public() -> None:
+    """``>X+local,<Y union ==X`` extends the lower bound down to ``X``
+    (inclusive). ``==X`` matches the literal point ``X`` and every
+    ``X+local`` variant, including the excluded ``X+local`` lower bound.
+    """
+    range_above = VersionRange(
+        Version.parse("0.21.0+cpu"),
+        Version.parse("0.22.0"),
+        include_min=False,
+        include_max=False,
+    )
+    public = Version.parse("0.21.0")
+    expected = VersionRange(
+        Version.parse("0.21.0"),
+        Version.parse("0.22.0"),
+        include_min=True,
+        include_max=False,
+    )
+    assert range_above.union(public) == expected
+    assert public.union(range_above) == expected
+
+
+def test_union_punctured_versionunion_with_public_collapses_puncture() -> None:
+    """End-to-end on a punctured ``VersionUnion``: ``==X`` fills the
+    interior puncture at ``X+local``, collapsing the two-range union
+    back to a single unpunctured range.
+    """
+    punctured = parse_constraint(">=0.21.0,!=0.21.0+cpu,<0.22.0")
+    public = parse_constraint("==0.21.0")
+    plain = parse_constraint(">=0.21.0,<0.22.0")
+    assert punctured.union(public) == plain
+    assert public.union(punctured) == plain
+
+
+def test_union_range_with_local_other_does_not_broaden() -> None:
+    """Negative control: a *local* ``==X+other`` matches only itself
+    literally, never sibling local-tagged versions. Unioning it with a
+    range that excludes a different ``X+local`` must preserve the
+    puncture rather than broaden.
+    """
+    range_below = VersionRange(
+        Version.parse("0.21.0"),
+        Version.parse("0.21.0+cpu"),
+        include_min=True,
+        include_max=False,
+    )
+    other_local = Version.parse("0.21.0+other")
+    result = range_below.union(other_local)
+    assert result.allows(Version.parse("0.21.0"))
+    assert result.allows(other_local)
+    assert not result.allows(Version.parse("0.21.0+cpu"))
+
+
 def test_parsed_strict_max_excludes_dev_releases_of_stable() -> None:
     """PEP 440: ``<V`` for stable V MUST NOT allow pre-/dev-releases of V.
     The parser canonicalizes to ``<V.dev0`` so ``allows`` reports correctly."""