Issue #21750: mock_open.read_data can now be read from each instance, as it

could in Python 3.3.

4 files changed, 64 insertions, 17 deletions

diff --git a/NEWS b/NEWS
index 90897a2..f3f0086 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,9 @@
+Library
+-------
+
+- Issue #21750: mock_open.read_data can now be read from each instance, as it
+  could in Python 3.3.
+
 - Issue #18622: unittest.mock.mock_open().reset_mock would recurse infinitely.
   Patch from Nicola Palumbo and Laurent De Buyst.
 
diff --git a/mock/mock.py b/mock/mock.py
index cd90dea..12016d4 100644
--- a/mock/mock.py
+++ b/mock/mock.py
@@ -2453,6 +2453,7 @@ def _iterate_read_data(read_data):
     for line in data_as_list:
         yield line
 
+
 def mock_open(mock=None, read_data=''):
     """
     A helper function to create a mock to replace the use of `open`. It works
@@ -2495,21 +2496,42 @@ def mock_open(mock=None, read_data=''):
     if mock is None:
         mock = MagicMock(name='open', spec=open)
 
-    handle = MagicMock(spec=file_spec)
-    handle.__enter__.return_value = handle
-
-    _data = _iterate_read_data(read_data)
-
-    handle.write.return_value = None
-    handle.read.return_value = None
-    handle.readline.return_value = None
-    handle.readlines.return_value = None
-
-    handle.read.side_effect = _read_side_effect
-    handle.readline.side_effect = _readline_side_effect()
-    handle.readlines.side_effect = _readlines_side_effect
-
-    mock.return_value = handle
+    def make_handle(*args, **kwargs):
+        # Arg checking is handled by __call__
+        def _readlines_side_effect(*args, **kwargs):
+            if handle.readlines.return_value is not None:
+                return handle.readlines.return_value
+            return list(_data)
+
+        def _read_side_effect(*args, **kwargs):
+            if handle.read.return_value is not None:
+                return handle.read.return_value
+            return ''.join(_data)
+
+        def _readline_side_effect():
+            if handle.readline.return_value is not None:
+                while True:
+                    yield handle.readline.return_value
+            for line in _data:
+                yield line
+
+        handle = MagicMock(spec=file_spec)
+        handle.__enter__.return_value = handle
+
+        _data = _iterate_read_data(read_data)
+
+        handle.write.return_value = None
+        handle.read.return_value = None
+        handle.readline.return_value = None
+        handle.readlines.return_value = None
+
+        handle.read.side_effect = _read_side_effect
+        handle.readline.side_effect = _readline_side_effect()
+        handle.readlines.side_effect = _readlines_side_effect
+        _check_and_set_parent(mock, handle, None, '()')
+        return handle
+
+    mock.side_effect = make_handle
     return mock
 
 
diff --git a/mock/tests/testmock.py b/mock/tests/testmock.py
index 4be8779..88f94f3 100644
--- a/mock/tests/testmock.py
+++ b/mock/tests/testmock.py
@@ -1436,6 +1436,11 @@ class MockTest(unittest.TestCase):
             self.assertEqual(m.mock_calls, [call.__int__(), call.__float__()])
             self.assertEqual(m.method_calls, [])
 
+    def test_mock_open_reuse_issue_21750(self):
+        mocked_open = mock.mock_open(read_data='data')
+        f1 = mocked_open('a-name')
+        f2 = mocked_open('another-name')
+        self.assertEqual(f1.read(), f2.read())
 
     def test_mock_parents(self):
         for Klass in Mock, MagicMock:
diff --git a/mock/tests/testwith.py b/mock/tests/testwith.py
index 25d706f..11e97bb 100644
--- a/mock/tests/testwith.py
+++ b/mock/tests/testwith.py
@@ -146,7 +146,6 @@ class TestMockOpen(unittest.TestCase):
 
     def test_mock_open_context_manager(self):
         mock = mock_open()
-        handle = mock.return_value
         with patch('%s.open' % __name__, mock, create=True):
             with open('foo') as f:
                 f.read()
@@ -154,8 +153,23 @@ class TestMockOpen(unittest.TestCase):
         expected_calls = [call('foo'), call().__enter__(), call().read(),
                           call().__exit__(None, None, None)]
         self.assertEqual(mock.mock_calls, expected_calls)
-        self.assertIs(f, handle)
+        # mock_open.return_value is no longer static, because
+        # readline support requires that it mutate state
 
+    def test_mock_open_context_manager_multiple_times(self):
+        mock = mock_open()
+        with patch('%s.open' % __name__, mock, create=True):
+            with open('foo') as f:
+                f.read()
+            with open('bar') as f:
+                f.read()
+
+        expected_calls = [
+            call('foo'), call().__enter__(), call().read(),
+            call().__exit__(None, None, None),
+            call('bar'), call().__enter__(), call().read(),
+            call().__exit__(None, None, None)]
+        self.assertEqual(mock.mock_calls, expected_calls)
 
     def test_explicit_mock(self):
         mock = MagicMock()