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
This commit is contained in:
Damien Nadé 2019-05-23 12:03:25 +02:00 committed by Miss Islington (bot)
parent 51aa35e9e1
commit 394119afc6
4 changed files with 36 additions and 0 deletions

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@ -2680,6 +2680,11 @@ def mock_open(mock=None, read_data=''):
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 @@ def mock_open(mock=None, read_data=''):
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)

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@ -1702,6 +1702,19 @@ class MockTest(unittest.TestCase):
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'))

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@ -230,7 +230,22 @@ class TestMockOpen(unittest.TestCase):
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

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@ -0,0 +1,2 @@
Add support for calling :func:`next` with the mock resulting from
:func:`unittest.mock.mock_open`