fix: ensure enums are incomparable w other enum types (#248)

Fixes #247.

proto/enums.py

@@ -108,7 +108,45 @@ def __new__(mcls, name, bases, attrs):
 class Enum(enum.IntEnum, metaclass=ProtoEnumMeta):
     """A enum object that also builds a protobuf enum descriptor."""
 
-    pass
+    def _comparable(self, other):
+        # Avoid 'isinstance' to prevent other IntEnums from matching
+        return type(other) in (type(self), int)
+
+    def __eq__(self, other):
+        if not self._comparable(other):
+            return NotImplemented
+
+        return self.value == int(other)
+
+    def __ne__(self, other):
+        if not self._comparable(other):
+            return NotImplemented
+
+        return self.value != int(other)
+
+    def __lt__(self, other):
+        if not self._comparable(other):
+            return NotImplemented
+
+        return self.value < int(other)
+
+    def __le__(self, other):
+        if not self._comparable(other):
+            return NotImplemented
+
+        return self.value <= int(other)
+
+    def __ge__(self, other):
+        if not self._comparable(other):
+            return NotImplemented
+
+        return self.value >= int(other)
+
+    def __gt__(self, other):
+        if not self._comparable(other):
+            return NotImplemented
+
+        return self.value > int(other)
 
 
 class _EnumInfo:

tests/enums_test.py

@@ -0,0 +1,28 @@
+# Copyright (C) 2021  Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import proto
+
+__protobuf__ = proto.module(package="test.proto", manifest={"Enums",},)
+
+
+class OneEnum(proto.Enum):
+    UNSPECIFIED = 0
+    SOME_VALUE = 1
+
+
+class OtherEnum(proto.Enum):
+    UNSPECIFIED = 0
+    APPLE = 1
+    BANANA = 2

tests/test_enum_total_ordering.py

@@ -0,0 +1,87 @@
+# Copyright 2021, Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+import enums_test
+
+
+def test_total_ordering_w_same_enum_type():
+    to_compare = enums_test.OneEnum.SOME_VALUE
+
+    for item in enums_test.OneEnum:
+        if item.value < to_compare.value:
+            assert not to_compare == item
+            assert to_compare != item
+            assert not to_compare < item
+            assert not to_compare <= item
+            assert to_compare > item
+            assert to_compare >= item
+        elif item.value > to_compare.value:
+            assert not to_compare == item
+            assert to_compare != item
+            assert to_compare < item
+            assert to_compare <= item
+            assert not to_compare > item
+            assert not to_compare >= item
+        else:  # item.value == to_compare.value:
+            assert to_compare == item
+            assert not to_compare != item
+            assert not to_compare < item
+            assert to_compare <= item
+            assert not to_compare > item
+            assert to_compare >= item
+
+
+def test_total_ordering_w_other_enum_type():
+    to_compare = enums_test.OneEnum.SOME_VALUE
+
+    for item in enums_test.OtherEnum:
+        assert not to_compare == item
+        assert to_compare.SOME_VALUE != item
+        with pytest.raises(TypeError):
+            assert not to_compare < item
+        with pytest.raises(TypeError):
+            assert not to_compare <= item
+        with pytest.raises(TypeError):
+            assert not to_compare > item
+        with pytest.raises(TypeError):
+            assert not to_compare >= item
+
+
+@pytest.mark.parametrize("int_val", range(-1, 3))
+def test_total_ordering_w_int(int_val):
+    to_compare = enums_test.OneEnum.SOME_VALUE
+
+    if int_val < to_compare.value:
+        assert not to_compare == int_val
+        assert to_compare != int_val
+        assert not to_compare < int_val
+        assert not to_compare <= int_val
+        assert to_compare > int_val
+        assert to_compare >= int_val
+    elif int_val > to_compare.value:
+        assert not to_compare == int_val
+        assert to_compare != int_val
+        assert to_compare < int_val
+        assert to_compare <= int_val
+        assert not to_compare > int_val
+        assert not to_compare >= int_val
+    else:  # int_val == to_compare.value:
+        assert to_compare == int_val
+        assert not to_compare != int_val
+        assert not to_compare < int_val
+        assert to_compare <= int_val
+        assert not to_compare > int_val
+        assert to_compare >= int_val