bpo-37008: make mock_open handle able to honor next() (GH-13492)
I've reported the issue on https://bugs.python.org/issue37008 and now I'm trying to bring a solution to this minor issue.
I think it could be trivially backported to 3.7 branch.
https://bugs.python.org/issue37008
diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 654462c..b14bf01 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -2680,6 +2680,11 @@
for line in _state[0]:
yield line
+ def _next_side_effect():
+ if handle.readline.return_value is not None:
+ return handle.readline.return_value
+ return next(_state[0])
+
global file_spec
if file_spec is None:
import _io
@@ -2701,6 +2706,7 @@
handle.readline.side_effect = _state[1]
handle.readlines.side_effect = _readlines_side_effect
handle.__iter__.side_effect = _iter_side_effect
+ handle.__next__.side_effect = _next_side_effect
def reset_data(*args, **kwargs):
_state[0] = _to_stream(read_data)
diff --git a/Lib/unittest/test/testmock/testmock.py b/Lib/unittest/test/testmock/testmock.py
index 307b8b7..0f30bcc 100644
--- a/Lib/unittest/test/testmock/testmock.py
+++ b/Lib/unittest/test/testmock/testmock.py
@@ -1702,6 +1702,19 @@
self.assertEqual(lines[1], 'Norwegian Blue')
self.assertEqual(list(f1), [])
+ def test_mock_open_using_next(self):
+ mocked_open = mock.mock_open(read_data='1st line\n2nd line\n3rd line')
+ f1 = mocked_open('a-name')
+ line1 = next(f1)
+ line2 = f1.__next__()
+ lines = [line for line in f1]
+ self.assertEqual(line1, '1st line\n')
+ self.assertEqual(line2, '2nd line\n')
+ self.assertEqual(lines[0], '3rd line')
+ self.assertEqual(list(f1), [])
+ with self.assertRaises(StopIteration):
+ next(f1)
+
def test_mock_open_write(self):
# Test exception in file writing write()
mock_namedtemp = mock.mock_open(mock.MagicMock(name='JLV'))
diff --git a/Lib/unittest/test/testmock/testwith.py b/Lib/unittest/test/testmock/testwith.py
index 5172c22..42ebf38 100644
--- a/Lib/unittest/test/testmock/testwith.py
+++ b/Lib/unittest/test/testmock/testwith.py
@@ -230,7 +230,22 @@
self.assertEqual(lines[1], 'bar\n')
self.assertEqual(lines[2], 'baz\n')
self.assertEqual(h.readline(), '')
+ with self.assertRaises(StopIteration):
+ next(h)
+ def test_next_data(self):
+ # Check that next will correctly return the next available
+ # line and plays well with the dunder_iter part.
+ mock = mock_open(read_data='foo\nbar\nbaz\n')
+ with patch('%s.open' % __name__, mock, create=True):
+ h = open('bar')
+ line1 = next(h)
+ line2 = next(h)
+ lines = [l for l in h]
+ self.assertEqual(line1, 'foo\n')
+ self.assertEqual(line2, 'bar\n')
+ self.assertEqual(lines[0], 'baz\n')
+ self.assertEqual(h.readline(), '')
def test_readlines_data(self):
# Test that emulating a file that ends in a newline character works
diff --git a/Misc/NEWS.d/next/Library/2019-05-22-15-26-08.bpo-37008.WPbv31.rst b/Misc/NEWS.d/next/Library/2019-05-22-15-26-08.bpo-37008.WPbv31.rst
new file mode 100644
index 0000000..42747ae
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-05-22-15-26-08.bpo-37008.WPbv31.rst
@@ -0,0 +1,2 @@
+Add support for calling :func:`next` with the mock resulting from
+:func:`unittest.mock.mock_open`