perf: cache results of cnf, dnf and _merge_single_markers

In order to cache `cnf` and `dnf`, we can no longer consider composite markers and constraints with the same sub elements but a different order to be equal
because order is relevant when building an intersection or union.
Neglecting order leads to different results if the result of an "equal" marker with a different order has already been cached.
This can even result in a RecursionError, as the test suite demonstrates.

src/poetry/core/constraints/generic/constraint.py

@@ -114,9 +114,9 @@ def intersect(self, other: BaseConstraint) -> BaseConstraint:
         return other.intersect(self)
 
     def union(self, other: BaseConstraint) -> BaseConstraint:
-        if isinstance(other, Constraint):
-            from poetry.core.constraints.generic.union_constraint import UnionConstraint
+        from poetry.core.constraints.generic.union_constraint import UnionConstraint
 
+        if isinstance(other, Constraint):
             if other == self:
                 return self
 
@@ -131,6 +131,10 @@ def union(self, other: BaseConstraint) -> BaseConstraint:
 
             return AnyConstraint()
 
+        # to preserve order (functionally not necessary)
+        if isinstance(other, UnionConstraint):
+            return UnionConstraint(self).union(other)
+
         return other.union(self)
 
     def is_any(self) -> bool:

src/poetry/core/constraints/generic/multi_constraint.py

@@ -125,7 +125,7 @@ def __eq__(self, other: object) -> bool:
         if not isinstance(other, MultiConstraint):
             return False
 
-        return set(self._constraints) == set(other._constraints)
+        return self._constraints == other._constraints
 
     def __hash__(self) -> int:
         h = hash("multi")

src/poetry/core/constraints/generic/union_constraint.py

@@ -134,13 +134,19 @@ def union(self, other: BaseConstraint) -> BaseConstraint:
             our_new_constraints: list[BaseConstraint] = []
             their_new_constraints: list[BaseConstraint] = []
             merged_new_constraints: list[BaseConstraint] = []
-            for our_constraint in self._constraints:
-                for their_constraint in other.constraints:
+            for their_constraint in other.constraints:
+                for our_constraint in self._constraints:
                     union = our_constraint.union(their_constraint)
                     if union.is_any():
                         return AnyConstraint()
                     if isinstance(union, Constraint):
-                        if union not in merged_new_constraints:
+                        if union == our_constraint:
+                            if union not in our_new_constraints:
+                                our_new_constraints.append(union)
+                        elif union == their_constraint:
+                            if union not in their_new_constraints:
+                                their_new_constraints.append(their_constraint)
+                        elif union not in merged_new_constraints:
                             merged_new_constraints.append(union)
                     else:
                         if our_constraint not in our_new_constraints:
@@ -169,7 +175,7 @@ def __eq__(self, other: object) -> bool:
         if not isinstance(other, UnionConstraint):
             return False
 
-        return set(self._constraints) == set(other._constraints)
+        return self._constraints == other._constraints
 
     def __hash__(self) -> int:
         h = hash("union")

src/poetry/core/version/markers.py

@@ -411,6 +411,15 @@ def invert(self) -> BaseMarker:
 
         return parse_marker(f"{self._name} {operator} '{self._value}'")
 
+    def __eq__(self, other: object) -> bool:
+        if not isinstance(other, SingleMarker):
+            return NotImplemented
+
+        return str(self) == str(other)
+
+    def __hash__(self) -> int:
+        return hash(str(self))
+
     def __str__(self) -> str:
         return f'{self._name} {self._operator} "{self._value}"'
 
@@ -643,7 +652,7 @@ def __eq__(self, other: object) -> bool:
         if not isinstance(other, MultiMarker):
             return False
 
-        return set(self._markers) == set(other.markers)
+        return self._markers == other.markers
 
     def __hash__(self) -> int:
         h = hash("multi")
@@ -823,7 +832,7 @@ def __eq__(self, other: object) -> bool:
         if not isinstance(other, MarkerUnion):
             return False
 
-        return set(self._markers) == set(other.markers)
+        return self._markers == other.markers
 
     def __hash__(self) -> int:
         h = hash("union")
@@ -896,6 +905,7 @@ def _compact_markers(
     return union(*sub_markers)
 
 
+@functools.lru_cache(maxsize=None)
 def cnf(marker: BaseMarker) -> BaseMarker:
     """Transforms the marker into CNF (conjunctive normal form)."""
     if isinstance(marker, MarkerUnion):
@@ -913,6 +923,7 @@ def cnf(marker: BaseMarker) -> BaseMarker:
     return marker
 
 
+@functools.lru_cache(maxsize=None)
 def dnf(marker: BaseMarker) -> BaseMarker:
     """Transforms the marker into DNF (disjunctive normal form)."""
     if isinstance(marker, MultiMarker):
@@ -955,6 +966,7 @@ def union(*markers: BaseMarker) -> BaseMarker:
     return min(disjunction, conjunction, unnormalized, key=lambda x: x.complexity)
 
 
+@functools.lru_cache(maxsize=None)
 def _merge_single_markers(
     marker1: SingleMarkerLike[SingleMarkerConstraint],
     marker2: SingleMarkerLike[SingleMarkerConstraint],

tests/constraints/generic/test_constraint.py

@@ -159,7 +159,10 @@ def test_invert(constraint: BaseConstraint, inverted: BaseConstraint) -> None:
         (
             Constraint("win32", "!="),
             Constraint("linux", "!="),
-            MultiConstraint(Constraint("win32", "!="), Constraint("linux", "!=")),
+            (
+                MultiConstraint(Constraint("win32", "!="), Constraint("linux", "!=")),
+                MultiConstraint(Constraint("linux", "!="), Constraint("win32", "!=")),
+            ),
         ),
         (
             Constraint("win32", "!="),
@@ -222,21 +225,30 @@ def test_invert(constraint: BaseConstraint, inverted: BaseConstraint) -> None:
         (
             MultiConstraint(Constraint("win32", "!="), Constraint("linux", "!=")),
             MultiConstraint(Constraint("win32", "!="), Constraint("darwin", "!=")),
-            MultiConstraint(
-                Constraint("win32", "!="),
-                Constraint("linux", "!="),
-                Constraint("darwin", "!="),
+            (
+                MultiConstraint(
+                    Constraint("win32", "!="),
+                    Constraint("linux", "!="),
+                    Constraint("darwin", "!="),
+                ),
+                MultiConstraint(
+                    Constraint("win32", "!="),
+                    Constraint("darwin", "!="),
+                    Constraint("linux", "!="),
+                ),
             ),
         ),
     ],
 )
 def test_intersect(
     constraint1: BaseConstraint,
     constraint2: BaseConstraint,
-    expected: BaseConstraint,
+    expected: BaseConstraint | tuple[BaseConstraint, BaseConstraint],
 ) -> None:
-    assert constraint1.intersect(constraint2) == expected
-    assert constraint2.intersect(constraint1) == expected
+    if not isinstance(expected, tuple):
+        expected = (expected, expected)
+    assert constraint1.intersect(constraint2) == expected[0]
+    assert constraint2.intersect(constraint1) == expected[1]
 
 
 @pytest.mark.parametrize(
@@ -295,7 +307,10 @@ def test_intersect(
         (
             Constraint("win32"),
             Constraint("linux"),
-            UnionConstraint(Constraint("win32"), Constraint("linux")),
+            (
+                UnionConstraint(Constraint("win32"), Constraint("linux")),
+                UnionConstraint(Constraint("linux"), Constraint("win32")),
+            ),
         ),
         (
             Constraint("win32"),
@@ -324,8 +339,13 @@ def test_intersect(
         (
             Constraint("win32"),
             UnionConstraint(Constraint("linux"), Constraint("linux2")),
-            UnionConstraint(
-                Constraint("win32"), Constraint("linux"), Constraint("linux2")
+            (
+                UnionConstraint(
+                    Constraint("win32"), Constraint("linux"), Constraint("linux2")
+                ),
+                UnionConstraint(
+                    Constraint("linux"), Constraint("linux2"), Constraint("win32")
+                ),
             ),
         ),
         (
@@ -366,8 +386,13 @@ def test_intersect(
         (
             UnionConstraint(Constraint("win32"), Constraint("linux")),
             UnionConstraint(Constraint("win32"), Constraint("darwin")),
-            UnionConstraint(
-                Constraint("win32"), Constraint("linux"), Constraint("darwin")
+            (
+                UnionConstraint(
+                    Constraint("win32"), Constraint("linux"), Constraint("darwin")
+                ),
+                UnionConstraint(
+                    Constraint("win32"), Constraint("darwin"), Constraint("linux")
+                ),
             ),
         ),
         (
@@ -377,11 +402,19 @@ def test_intersect(
             UnionConstraint(
                 Constraint("win32"), Constraint("cygwin"), Constraint("darwin")
             ),
-            UnionConstraint(
-                Constraint("win32"),
-                Constraint("linux"),
-                Constraint("darwin"),
-                Constraint("cygwin"),
+            (
+                UnionConstraint(
+                    Constraint("win32"),
+                    Constraint("linux"),
+                    Constraint("darwin"),
+                    Constraint("cygwin"),
+                ),
+                UnionConstraint(
+                    Constraint("win32"),
+                    Constraint("cygwin"),
+                    Constraint("darwin"),
+                    Constraint("linux"),
+                ),
             ),
         ),
         (
@@ -412,10 +445,12 @@ def test_intersect(
 def test_union(
     constraint1: BaseConstraint,
     constraint2: BaseConstraint,
-    expected: BaseConstraint,
+    expected: BaseConstraint | tuple[BaseConstraint, BaseConstraint],
 ) -> None:
-    assert constraint1.union(constraint2) == expected
-    assert constraint2.union(constraint1) == expected
+    if not isinstance(expected, tuple):
+        expected = (expected, expected)
+    assert constraint1.union(constraint2) == expected[0]
+    assert constraint2.union(constraint1) == expected[1]
 
 
 def test_difference() -> None:

tests/version/test_markers.py

@@ -1312,8 +1312,8 @@ def test_union_should_drop_markers_if_their_complement_is_present(
                 ),
                 MarkerUnion(
                     SingleMarker("python_version", "<3.7"),
-                    SingleMarker("sys_platform", "!=linux"),
                     SingleMarker("python_version", ">=3.9"),
+                    SingleMarker("sys_platform", "!=linux"),
                 ),
             ),
         ),