bpo-46388: Test NotImplemented code path for functools.total_ordering (…

…GH-30616)

Lib/test/test_functools.py

@@ -1049,6 +1049,73 @@ def test_no_operations_defined(self):
             class A:
                 pass
 
+    def test_notimplemented(self):
+        # Verify NotImplemented results are correctly handled
+        @functools.total_ordering
+        class ImplementsLessThan:
+            def __init__(self, value):
+                self.value = value
+            def __eq__(self, other):
+                if isinstance(other, ImplementsLessThan):
+                    return self.value == other.value
+                return False
+            def __lt__(self, other):
+                if isinstance(other, ImplementsLessThan):
+                    return self.value < other.value
+                return NotImplemented
+
+        @functools.total_ordering
+        class ImplementsLessThanEqualTo:
+            def __init__(self, value):
+                self.value = value
+            def __eq__(self, other):
+                if isinstance(other, ImplementsLessThanEqualTo):
+                    return self.value == other.value
+                return False
+            def __le__(self, other):
+                if isinstance(other, ImplementsLessThanEqualTo):
+                    return self.value <= other.value
+                return NotImplemented
+
+        @functools.total_ordering
+        class ImplementsGreaterThan:
+            def __init__(self, value):
+                self.value = value
+            def __eq__(self, other):
+                if isinstance(other, ImplementsGreaterThan):
+                    return self.value == other.value
+                return False
+            def __gt__(self, other):
+                if isinstance(other, ImplementsGreaterThan):
+                    return self.value > other.value
+                return NotImplemented
+
+        @functools.total_ordering
+        class ImplementsGreaterThanEqualTo:
+            def __init__(self, value):
+                self.value = value
+            def __eq__(self, other):
+                if isinstance(other, ImplementsGreaterThanEqualTo):
+                    return self.value == other.value
+                return False
+            def __ge__(self, other):
+                if isinstance(other, ImplementsGreaterThanEqualTo):
+                    return self.value >= other.value
+                return NotImplemented
+
+        self.assertIs(ImplementsLessThan(1).__le__(1), NotImplemented)
+        self.assertIs(ImplementsLessThan(1).__gt__(1), NotImplemented)
+        self.assertIs(ImplementsLessThan(1).__ge__(1), NotImplemented)
+        self.assertIs(ImplementsLessThanEqualTo(1).__lt__(1), NotImplemented)
+        self.assertIs(ImplementsLessThanEqualTo(1).__gt__(1), NotImplemented)
+        self.assertIs(ImplementsLessThanEqualTo(1).__ge__(1), NotImplemented)
+        self.assertIs(ImplementsGreaterThan(1).__lt__(1), NotImplemented)
+        self.assertIs(ImplementsGreaterThan(1).__gt__(1), NotImplemented)
+        self.assertIs(ImplementsGreaterThan(1).__ge__(1), NotImplemented)
+        self.assertIs(ImplementsGreaterThanEqualTo(1).__lt__(1), NotImplemented)
+        self.assertIs(ImplementsGreaterThanEqualTo(1).__le__(1), NotImplemented)
+        self.assertIs(ImplementsGreaterThanEqualTo(1).__gt__(1), NotImplemented)
+
     def test_type_error_when_not_implemented(self):
         # bug 10042; ensure stack overflow does not occur
         # when decorated types return NotImplemented