bpo-44185: Added close() to mock_open __exit__ (#26902)

Backports: 3f7c0810f6158a7ff37be432f8d7f9511427489f
Signed-off-by: Chris Withers <chris@simplistix.co.uk>

NEWS.d/2021-06-24-20-45-03.bpo-44185.ZHb8yJ.rst

@@ -0,0 +1,3 @@
+:func:`unittest.mock.mock_open` will call the :func:`close` method of the file
+handle mock when it is exiting from the context manager.
+Patch by Samet Yaslan.

mock/mock.py

@@ -2994,6 +2994,9 @@ def _next_side_effect():
             return handle.readline.return_value
         return next(_state[0])
 
+    def _exit_side_effect(exctype, excinst, exctb):
+        handle.close()
+
     global file_spec
     if file_spec is None:
         import _io
@@ -3020,6 +3023,7 @@ def _next_side_effect():
     handle.readlines.side_effect = _readlines_side_effect
     handle.__iter__.side_effect = _iter_side_effect
     handle.__next__.side_effect = _next_side_effect
+    handle.__exit__.side_effect = _exit_side_effect
 
     def reset_data(*args, **kwargs):
         _state[0] = _to_stream(read_data)

mock/tests/testwith.py

@@ -158,7 +158,7 @@ def test_mock_open_context_manager(self):
                 f.read()
 
         expected_calls = [call('foo'), call().__enter__(), call().read(),
-                          call().__exit__(None, None, None)]
+                          call().__exit__(None, None, None), call().close()]
         self.assertEqual(mock.mock_calls, expected_calls)
         self.assertIs(f, handle)
 
@@ -172,9 +172,9 @@ def test_mock_open_context_manager_multiple_times(self):
 
         expected_calls = [
             call('foo'), call().__enter__(), call().read(),
-            call().__exit__(None, None, None),
+            call().__exit__(None, None, None), call().close(),
             call('bar'), call().__enter__(), call().read(),
-            call().__exit__(None, None, None)]
+            call().__exit__(None, None, None), call().close()]
         self.assertEqual(mock.mock_calls, expected_calls)
 
     def test_explicit_mock(self):