Refactor AsyncMock setup logic in create_autospec

[tirkarthi]

BPO	37047
Nosy	@cjw296, @voidspace, @asvetlov, @1st1, @lisroach, @mariocj89, @tirkarthi
PRs	bpo-37047: Refactor AsyncMock setup logic for autospeccing #13574

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2019-05-27.12:56:57.361>
created_at = <Date 2019-05-25.19:38:44.818>
labels = ['3.8', 'type-bug', 'library']
title = 'Refactor AsyncMock setup logic in create_autospec'
updated_at = <Date 2019-05-27.12:56:57.360>
user = 'https://github.com/tirkarthi'

bugs.python.org fields:

activity = <Date 2019-05-27.12:56:57.360>
actor = 'yselivanov'
assignee = 'none'
closed = True
closed_date = <Date 2019-05-27.12:56:57.361>
closer = 'yselivanov'
components = ['Library (Lib)']
creation = <Date 2019-05-25.19:38:44.818>
creator = 'xtreak'
dependencies = []
files = []
hgrepos = []
issue_num = 37047
keywords = ['patch']
message_count = 2.0
messages = ['343504', '343620']
nosy_count = 7.0
nosy_names = ['cjw296', 'michael.foord', 'asvetlov', 'yselivanov', 'lisroach', 'mariocj89', 'xtreak']
pr_nums = ['13574']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue37047'
versions = ['Python 3.8']

[tirkarthi]

• In create_autospec there is some logic to detect if the function is an async function this could be refactored out as a private function.

• create_autospec has initialization code for async mock. For synchronous functions this is done with _setup_func and is called during setting signature. AsyncMock needs different setup logic code to setup the functions but the code can be refactored out of create_autospec into _setup_async_func.

• In create_autospec awaited attribute is not set for AsyncMock during setup [0] and hence this causes AttributeError when the coroutine is awaited. awaited attribute can be also initialized.

import asyncio
from unittest.mock import create_autospec

async def foo(): pass

spec = create_autospec(foo)
awaitable = spec()

async def main(): await awaitable

asyncio.run(main())

Traceback (most recent call last):
  File "/tmp/spam.py", line 13, in <module>
    asyncio.run(main())
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/asyncio/runners.py", line 43, in run
    return loop.run_until_complete(main)
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/asyncio/base_events.py", line 614, in run_until_complete
    return future.result()
  File "/tmp/spam.py", line 11, in main
    await awaitable
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/unittest/mock.py", line 2045, in _mock_call
    return await proxy()
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/unittest/mock.py", line 2043, in proxy
    await self.awaited._notify()
  File "/Users/karthikeyansingaravelan/stuff/python/cpython/Lib/unittest/mock.py", line 596, in __getattr__
    raise AttributeError("Mock object has no attribute %r" % name)
AttributeError: Mock object has no attribute 'awaited'

• In the setup logic to create attributes like assert_not_awaited uses the pattern setattr(mock, a, f) at [1] . But due to late binding 'a' in the function f has the last value of the loop 'assert_not_awaited' and hence calling other helpers also calls assert_not_awaited. This could be resolved by using a partial function that binds the attribute value early in the loop and respective function would be used in getattr.

>>> spec.assert_awaited_once_with(1) # Due to late binding assert_not_awaited is always called
TypeError: assert_not_awaited() takes 1 positional argument but 2 were given

• assert_not_awaited has the error message indicating it should be awaited once [2] . This can be changed to indicate something like "Expected mock to not have been awaited".

>>> spec.assert_not_awaited()
AssertionError: Expected mock to have been awaited once. Awaited 1 times.

• mock docs have list of magic methods implemented where __aenter__, __aexit__, __aiter__ and __anext__ could be documented with versionadded directive. [3]

I have a PR with the above changes that I will post shortly for review.

[0]

cpython/Lib/unittest/mock.py

Line 2506 in 7114c65

mock._is_coroutine = asyncio.coroutines._is_coroutine

[1]

cpython/Lib/unittest/mock.py

Line 2518 in 7114c65

def f(*args, **kwargs):

[2]

cpython/Lib/unittest/mock.py

Line 2154 in 7114c65

msg = (f"Expected {self._mock_name or 'mock'} to have been awaited once."

[3] https://docs.python.org/3.8/library/unittest.mock.html#mocking-magic-methods

[1st1]

New changeset ff6b2e6 by Yury Selivanov (Xtreak) in branch 'master':
bpo-37047: Refactor AsyncMock setup logic for autospeccing (GH-13574)
ff6b2e6