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bpo-31855: unittest.mock.mock_open() results now respects the argument of read([size]) #11521

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Merged
merged 4 commits into from
May 7, 2019
Merged

bpo-31855: unittest.mock.mock_open() results now respects the argument of read([size]) #11521

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fe5c357
unittest.mock.mock_open() results now respects the argument of read([…
Jan 11, 2019
ee7d67a
Add test for successive reads
May 6, 2019
59b08e6
Remove code duplication
May 6, 2019
b48ed55
Update Misc/NEWS.d/next/Library/2019-01-11-17-09-15.bpo-31855.PlhfsX.rst
tirkarthi May 6, 2019
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39 changes: 14 additions & 25 deletions Lib/unittest/mock.py
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
__version__ = '1.0'


import io
import inspect
import pprint
import sys
Expand Down Expand Up @@ -2346,25 +2347,12 @@ def __init__(self, spec, spec_set=False, parent=None,

file_spec = None

def _iterate_read_data(read_data):
# Helper for mock_open:
# Retrieve lines from read_data via a generator so that separate calls to
# readline, read, and readlines are properly interleaved
sep = b'\n' if isinstance(read_data, bytes) else '\n'
data_as_list = [l + sep for l in read_data.split(sep)]

if data_as_list[-1] == sep:
# If the last line ended in a newline, the list comprehension will have an
# extra entry that's just a newline. Remove this.
data_as_list = data_as_list[:-1]
else:
# If there wasn't an extra newline by itself, then the file being
# emulated doesn't have a newline to end the last line remove the
# newline that our naive format() added
data_as_list[-1] = data_as_list[-1][:-1]

for line in data_as_list:
yield line
def _to_stream(read_data):
if isinstance(read_data, bytes):
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Code LGTM. I am slightly concerned if there might be any problems with backport where in Python 2 bytes is like an alias for str. So, even with BytesIO it would still be string as shown below and work as expected. Maybe I am just overthinking this.

It would be helpful if @cjw296 and @voidspace can review this since this is a good bug to be fixed. Thanks @remilapeyre .

$ python2
Python 2.7.6 (default, Sep  9 2014, 15:04:36)
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> isinstance('a', bytes)
True
>>> isinstance(b'a', str)
True
>>> import io
>>> io.BytesIO('a').readline()
'a'
>>> type(io.BytesIO('a').readline())
<type 'str'>

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Don't worry, we can make this work in the backport :-)

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@tirkarthi wouldn't it still be correct? The test would be useless be the mock would still work right?

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yes, in Python 2 str and bytes are the same. I will just keep on the CI once the backport lands in mock repo.

return io.BytesIO(read_data)
else:
return io.StringIO(read_data)


def mock_open(mock=None, read_data=''):
Expand All @@ -2379,20 +2367,23 @@ def mock_open(mock=None, read_data=''):
`read_data` is a string for the `read`, `readline` and `readlines` of the
file handle to return. This is an empty string by default.
"""
_read_data = _to_stream(read_data)
_state = [_read_data, None]

def _readlines_side_effect(*args, **kwargs):
if handle.readlines.return_value is not None:
return handle.readlines.return_value
return list(_state[0])
return _state[0].readlines(*args, **kwargs)

def _read_side_effect(*args, **kwargs):
if handle.read.return_value is not None:
return handle.read.return_value
return type(read_data)().join(_state[0])
return _state[0].read(*args, **kwargs)

def _readline_side_effect():
def _readline_side_effect(*args, **kwargs):
yield from _iter_side_effect()
while True:
yield type(read_data)()
yield _state[0].readline(*args, **kwargs)

def _iter_side_effect():
if handle.readline.return_value is not None:
Expand All @@ -2412,8 +2403,6 @@ def _iter_side_effect():
handle = MagicMock(spec=file_spec)
handle.__enter__.return_value = handle

_state = [_iterate_read_data(read_data), None]

handle.write.return_value = None
handle.read.return_value = None
handle.readline.return_value = None
Expand All @@ -2426,7 +2415,7 @@ def _iter_side_effect():
handle.__iter__.side_effect = _iter_side_effect

def reset_data(*args, **kwargs):
_state[0] = _iterate_read_data(read_data)
_state[0] = _to_stream(read_data)
if handle.readline.side_effect == _state[1]:
# Only reset the side effect if the user hasn't overridden it.
_state[1] = _readline_side_effect()
Expand Down
7 changes: 6 additions & 1 deletion Lib/unittest/test/testmock/testwith.py
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Original file line number Diff line number Diff line change
Expand Up @@ -286,7 +286,12 @@ def test_mock_open_read_with_argument(self):
# for mocks returned by mock_open
some_data = 'foo\nbar\nbaz'
mock = mock_open(read_data=some_data)
self.assertEqual(mock().read(10), some_data)
self.assertEqual(mock().read(10), some_data[:10])
self.assertEqual(mock().read(10), some_data[:10])

f = mock()
self.assertEqual(f.read(10), some_data[:10])
self.assertEqual(f.read(10), some_data[10:])


def test_interleaved_reads(self):
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2019-01-11-17-09-15.bpo-31855.PlhfsX.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
:func:`unittest.mock.mock_open` results now respects the argument of read([size]).
Patch contributed by Rémi Lapeyre.