Fix equality comparison of WriteConcern objects. (#378)

pymongo/write_concern.py

@@ -113,10 +113,14 @@ class WriteConcern(object):
             ", ".join("%s=%s" % kvt for kvt in self.__document.items()),))
 
     def __eq__(self, other):
-        return self.__document == other.document
+        if isinstance(other, WriteConcern):
+            return self.__document == other.document
+        return NotImplemented
 
     def __ne__(self, other):
-        return self.__document != other.document
+        if isinstance(other, WriteConcern):
+            return self.__document != other.document
+        return NotImplemented
 
 
 DEFAULT_WRITE_CONCERN = WriteConcern()

test/test_write_concern.py

@@ -0,0 +1,67 @@
+# Copyright 2018-present MongoDB, Inc.
+#
+# 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.
+
+"""Run the unit tests for WriteConcern."""
+
+import collections
+import unittest
+
+from pymongo.write_concern import WriteConcern
+
+
+class TestWriteConcern(unittest.TestCase):
+
+    def test_equality(self):
+        concern = WriteConcern(j=True, wtimeout=3000)
+        self.assertEqual(concern, WriteConcern(j=True, wtimeout=3000))
+        self.assertNotEqual(concern, WriteConcern())
+
+    def test_equality_to_none(self):
+        concern = WriteConcern()
+        self.assertNotEqual(concern, None)
+        # Explicitly use the != operator.
+        self.assertTrue(concern != None)  # noqa
+
+    def test_equality_compatible_type(self):
+
+        class _FakeWriteConcern(object):
+
+            def __init__(self, **document):
+                self.document = document
+
+            def __eq__(self, other):
+                try:
+                    return self.document == other.document
+                except AttributeError:
+                    return NotImplemented
+
+            def __ne__(self, other):
+                try:
+                    return self.document != other.document
+                except AttributeError:
+                    return NotImplemented
+
+        self.assertEqual(WriteConcern(j=True), _FakeWriteConcern(j=True))
+        self.assertEqual(_FakeWriteConcern(j=True), WriteConcern(j=True))
+        self.assertEqual(WriteConcern(j=True), _FakeWriteConcern(j=True))
+        self.assertEqual(WriteConcern(wtimeout=42), _FakeWriteConcern(wtimeout=42))
+        self.assertNotEqual(WriteConcern(wtimeout=42), _FakeWriteConcern(wtimeout=2000))
+
+    def test_equality_incompatible_type(self):
+        _fake_type = collections.namedtuple('NotAWriteConcern', ['document'])
+        self.assertNotEqual(WriteConcern(j=True), _fake_type({'j': True}))
+
+
+if __name__ == '__main__':
+    unittest.main()