perf: return least complex marker when building intersection

src/poetry/core/version/markers.py

@@ -744,7 +744,7 @@ def exclude(self, marker_name: str) -> BaseMarker:
             if not marker.is_empty():
                 new_markers.append(marker)
 
-        return self.of(*new_markers)
+        return intersection(*new_markers)
 
     def only(self, *marker_names: str) -> BaseMarker:
         return self.of(*(m.only(*marker_names) for m in self._markers))
@@ -920,7 +920,7 @@ def exclude(self, marker_name: str) -> BaseMarker:
             # All markers were the excluded marker.
             return AnyMarker()
 
-        return self.of(*new_markers)
+        return union(*new_markers)
 
     def only(self, *marker_names: str) -> BaseMarker:
         return self.of(*(m.only(*marker_names) for m in self._markers))
@@ -1076,11 +1076,28 @@ def dnf(marker: BaseMarker) -> BaseMarker:
 
 
 def intersection(*markers: BaseMarker) -> BaseMarker:
-    return dnf(MultiMarker(*markers))
+    # Sometimes normalization makes it more complicated instead of simple
+    # -> choose candidate with the least complexity
+    unnormalized: BaseMarker = MultiMarker(*markers)
+    while (
+        isinstance(unnormalized, (MultiMarker, MarkerUnion))
+        and len(unnormalized.markers) == 1
+    ):
+        unnormalized = unnormalized.markers[0]
+
+    disjunction = dnf(unnormalized)
+    if not isinstance(disjunction, MarkerUnion):
+        return disjunction
+
+    conjunction = cnf(disjunction)
+    if not isinstance(conjunction, MultiMarker):
+        return conjunction
+
+    return min(disjunction, conjunction, unnormalized, key=lambda x: x.complexity)
 
 
 def union(*markers: BaseMarker) -> BaseMarker:
-    # Sometimes normalization makes it more complicate instead of simple
+    # Sometimes normalization makes it more complicated instead of simple
     # -> choose candidate with the least complexity
     unnormalized: BaseMarker = MarkerUnion(*markers)
     while (

tests/version/test_markers.py

@@ -940,9 +940,8 @@ def test_marker_union_intersect_single_marker() -> None:
 
     intersection = m.intersect(parse_marker('implementation_name == "cpython"'))
     assert (
-        str(intersection)
-        == 'sys_platform == "darwin" and implementation_name == "cpython" '
-        'or python_version < "3.4" and implementation_name == "cpython"'
+        str(intersection) == '(sys_platform == "darwin" or python_version < "3.4")'
+        ' and implementation_name == "cpython"'
     )
 
 
@@ -968,11 +967,8 @@ def test_marker_union_intersect_marker_union() -> None:
         parse_marker('implementation_name == "cpython" or os_name == "Windows"')
     )
     assert (
-        str(intersection)
-        == 'sys_platform == "darwin" and implementation_name == "cpython" '
-        'or sys_platform == "darwin" and os_name == "Windows" or '
-        'python_version < "3.4" and implementation_name == "cpython" or '
-        'python_version < "3.4" and os_name == "Windows"'
+        str(intersection) == '(sys_platform == "darwin" or python_version < "3.4") and '
+        '(implementation_name == "cpython" or os_name == "Windows")'
     )
 
 
@@ -1000,18 +996,16 @@ def test_marker_union_intersect_multi_marker() -> None:
 
     # Intersection isn't _quite_ symmetrical.
     expected1 = (
-        'sys_platform == "darwin" and implementation_name == "cpython" and os_name =='
-        ' "Windows" or python_version < "3.4" and implementation_name == "cpython" and'
-        ' os_name == "Windows"'
+        '(sys_platform == "darwin" or python_version < "3.4")'
+        ' and implementation_name == "cpython" and os_name == "Windows"'
     )
 
     intersection = m1.intersect(m2)
     assert str(intersection) == expected1
 
     expected2 = (
-        'implementation_name == "cpython" and os_name == "Windows" and sys_platform'
-        ' == "darwin" or implementation_name == "cpython" and os_name == "Windows"'
-        ' and python_version < "3.4"'
+        'implementation_name == "cpython" and os_name == "Windows"'
+        ' and (sys_platform == "darwin" or python_version < "3.4")'
     )
 
     intersection = m2.intersect(m1)
@@ -1357,6 +1351,18 @@ def test_without_extras(marker: str, expected: str) -> None:
             "extra",
             'python_version >= "3.6"',
         ),
+        (
+            (
+                'python_version >= "2.7" and (python_version < "2.8"'
+                ' or python_version >= "3.7") and python_version < "3.8"'
+                ' and extra == "foo"'
+            ),
+            "extra",
+            (
+                'python_version >= "2.7" and python_version < "2.8"'
+                ' or python_version >= "3.7" and python_version < "3.8"'
+            ),
+        ),
     ],
 )
 def test_exclude(marker: str, excluded: str, expected: str) -> None: