improve detection of Any marker union

Author: dimbleby

src/poetry/core/version/markers.py

@@ -558,7 +558,7 @@ def of(cls, *markers: BaseMarker) -> MarkerTypes:
                 continue
 
             if isinstance(marker, SingleMarker) and marker.name == "python_version":
-                intersected = False
+                included = False
                 for i, mark in enumerate(markers):
                     if (
                         not isinstance(mark, SingleMarker)
@@ -567,16 +567,18 @@ def of(cls, *markers: BaseMarker) -> MarkerTypes:
                     ):
                         continue
 
-                    intersection = mark.constraint.union(marker.constraint)
-                    if intersection == mark.constraint:
-                        intersected = True
+                    union = mark.constraint.union(marker.constraint)
+                    if union == mark.constraint:
+                        included = True
                         break
-                    elif intersection == marker.constraint:
+                    elif union == marker.constraint:
                         markers[i] = marker
-                        intersected = True
+                        included = True
                         break
+                    elif union.is_any():
+                        return AnyMarker()
 
-                if intersected:
+                if included:
                     continue
 
             markers.append(marker)

tests/version/test_markers.py

@@ -162,16 +162,13 @@ def test_single_marker_not_in_python_intersection():
 def test_single_marker_union():
     m = parse_marker('sys_platform == "darwin"')
 
-    intersection = m.union(parse_marker('implementation_name == "cpython"'))
-    assert (
-        str(intersection)
-        == 'sys_platform == "darwin" or implementation_name == "cpython"'
-    )
+    union = m.union(parse_marker('implementation_name == "cpython"'))
+    assert str(union) == 'sys_platform == "darwin" or implementation_name == "cpython"'
 
     m = parse_marker('python_version >= "3.4"')
 
-    intersection = m.union(parse_marker('python_version < "3.6"'))
-    assert str(intersection) == 'python_version >= "3.4" or python_version < "3.6"'
+    union = m.union(parse_marker('python_version < "3.6"'))
+    assert union.is_any()
 
 
 def test_single_marker_union_compacts_constraints():