performance fix for simplified marker simplifications

src/poetry/core/version/markers.py

@@ -420,7 +420,18 @@ def of(cls, *markers: BaseMarker) -> BaseMarker:
                             intersected = True
                             break
 
+                    # If we have a MarkerUnion then we can look for the simplifications
+                    # implemented in intersect_simplify().
+                    elif isinstance(mark, MarkerUnion):
+                        intersection = mark.intersect_simplify(marker)
+                        if intersection is not None:
+                            new_markers[i] = intersection
+                            intersected = True
+                            break
+
                 if intersected:
+                    # flatten again because intersect_simplify may return a multi
+                    new_markers = _flatten_markers(new_markers, MultiMarker)
                     continue
 
                 new_markers.append(marker)
@@ -451,6 +462,9 @@ def union_simplify(self, other: BaseMarker) -> BaseMarker | None:
 
             - union between two multimarkers where one is contained by the other is just
               the larger of the two
+
+            - union between two multimarkers where there are some common markers
+              and the union of unique markers is a single marker
         """
         if other in self._markers:
             return other
@@ -465,6 +479,22 @@ def union_simplify(self, other: BaseMarker) -> BaseMarker | None:
             if their_markers.issubset(our_markers):
                 return other
 
+            shared_markers = our_markers.intersection(their_markers)
+            if not shared_markers:
+                return None
+
+            unique_markers = our_markers - their_markers
+            other_unique_markers = their_markers - our_markers
+            unique_union = MultiMarker(*unique_markers).union(
+                MultiMarker(*other_unique_markers)
+            )
+            if isinstance(unique_union, (SingleMarker, AnyMarker)):
+                # Use list instead of set for deterministic order.
+                common_markers = [
+                    marker for marker in self.markers if marker in shared_markers
+                ]
+                return unique_union.intersect(MultiMarker(*common_markers))
+
         return None
 
     def validate(self, environment: dict[str, Any] | None) -> bool:
@@ -596,6 +626,50 @@ def intersect(self, other: BaseMarker) -> BaseMarker:
     def union(self, other: BaseMarker) -> BaseMarker:
         return union(self, other)
 
+    def intersect_simplify(self, other: BaseMarker) -> BaseMarker | None:
+        """
+        Finds a couple of easy simplifications for intersection on MarkerUnions:
+
+            - intersection with any marker that appears as part of the union is just
+              that marker
+
+            - intersection between two markerunions where one is contained by the other
+              is just the smaller of the two
+
+            - intersection between two markerunions where there are some common markers
+              and the intersection of unique markers is not a single marker
+        """
+        if other in self._markers:
+            return other
+
+        if isinstance(other, MarkerUnion):
+            our_markers = set(self.markers)
+            their_markers = set(other.markers)
+
+            if our_markers.issubset(their_markers):
+                return self
+
+            if their_markers.issubset(our_markers):
+                return other
+
+            shared_markers = our_markers.intersection(their_markers)
+            if not shared_markers:
+                return None
+
+            unique_markers = our_markers - their_markers
+            other_unique_markers = their_markers - our_markers
+            unique_intersection = MarkerUnion(*unique_markers).intersect(
+                MarkerUnion(*other_unique_markers)
+            )
+            if isinstance(unique_intersection, (SingleMarker, EmptyMarker)):
+                # Use list instead of set for deterministic order.
+                common_markers = [
+                    marker for marker in self.markers if marker in shared_markers
+                ]
+                return unique_intersection.union(MarkerUnion(*common_markers))
+
+        return None
+
     def validate(self, environment: dict[str, Any] | None) -> bool:
         return any(m.validate(environment) for m in self._markers)
 

tests/packages/utils/test_utils.py

@@ -25,8 +25,8 @@
             {
                 "python_version": [
                     [("<", "3.6")],
-                    [("<", "3.3")],
                     [("<", "3.6"), (">=", "3.3")],
+                    [("<", "3.3")],
                 ],
                 "sys_platform": [
                     [("==", "win32")],

tests/version/test_markers.py

@@ -13,7 +13,9 @@
 from poetry.core.version.markers import SingleMarker
 from poetry.core.version.markers import cnf
 from poetry.core.version.markers import dnf
+from poetry.core.version.markers import intersection
 from poetry.core.version.markers import parse_marker
+from poetry.core.version.markers import union
 
 
 if TYPE_CHECKING:
@@ -1285,11 +1287,6 @@ def test_union_should_drop_markers_if_their_complement_is_present(
                 ),
             ),
             MultiMarker(
-                MarkerUnion(
-                    SingleMarker("sys_platform", "!=win32"),
-                    SingleMarker("python_version", "<3.8"),
-                    SingleMarker("python_version", ">=3.9"),
-                ),
                 MarkerUnion(
                     SingleMarker("python_version", "<3.8"),
                     SingleMarker("python_version", ">=3.9"),
@@ -1556,6 +1553,68 @@ def test_empty_marker_is_found_in_complex_parse() -> None:
     assert marker.is_empty()
 
 
+def test_complex_union() -> None:
+    # real world example on the way to get mutually exclusive markers
+    # for numpy(>=1.21.2) of https://pypi.org/project/opencv-python/4.6.0.66/
+    markers = [
+        parse_marker(m)
+        for m in [
+            (
+                'python_version < "3.7" and python_version >= "3.6"'
+                ' and platform_system == "Darwin" and platform_machine == "arm64"'
+            ),
+            (
+                'python_version >= "3.10" or python_version >= "3.9"'
+                ' and platform_system == "Darwin" and platform_machine == "arm64"'
+            ),
+            (
+                'python_version >= "3.8" and platform_system == "Darwin"'
+                ' and platform_machine == "arm64" and python_version < "3.9"'
+            ),
+            (
+                'python_version >= "3.7" and platform_system == "Darwin"'
+                ' and platform_machine == "arm64" and python_version < "3.8"'
+            ),
+        ]
+    ]
+    assert (
+        str(union(*markers))
+        == 'platform_system == "Darwin" and platform_machine == "arm64"'
+        ' and python_version >= "3.6" or python_version >= "3.10"'
+    )
+
+
+def test_complex_intersection() -> None:
+    # inverse of real world example on the way to get mutually exclusive markers
+    # for numpy(>=1.21.2) of https://pypi.org/project/opencv-python/4.6.0.66/
+    markers = [
+        parse_marker(m).invert()
+        for m in [
+            (
+                'python_version < "3.7" and python_version >= "3.6"'
+                ' and platform_system == "Darwin" and platform_machine == "arm64"'
+            ),
+            (
+                'python_version >= "3.10" or python_version >= "3.9"'
+                ' and platform_system == "Darwin" and platform_machine == "arm64"'
+            ),
+            (
+                'python_version >= "3.8" and platform_system == "Darwin"'
+                ' and platform_machine == "arm64" and python_version < "3.9"'
+            ),
+            (
+                'python_version >= "3.7" and platform_system == "Darwin"'
+                ' and platform_machine == "arm64" and python_version < "3.8"'
+            ),
+        ]
+    ]
+    assert (
+        str(dnf(intersection(*markers).invert()))
+        == 'platform_system == "Darwin" and platform_machine == "arm64"'
+        ' and python_version >= "3.6" or python_version >= "3.10"'
+    )
+
+
 @pytest.mark.parametrize(
     "python_version, python_full_version, "
     "expected_intersection_version, expected_union_version",