unittest.mock.call does not chain __getitem__ to another _Call object

[blhsing]

BPO	37972
Nosy	@cjw296, @voidspace, @mariocj89, @tirkarthi, @blhsing
PRs	bpo-37972: unittest.mock._Call now passes on __getitem__ to the __getattr__ chaining so that call() can be subscriptable #15565 [3.8] bpo-37972: unittest.mock._Call now passes on __getitem__ to the __getattr__ chaining so that call() can be subscriptable (GH-15565) #15965

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

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GitHub fields:

assignee = None
closed_at = <Date 2019-10-10.14:40:24.310>
created_at = <Date 2019-08-28.20:33:01.517>
labels = ['3.8', 'type-bug', 'library', '3.9']
title = 'unittest.mock.call does not chain __getitem__ to another _Call object'
updated_at = <Date 2020-01-29.16:25:00.824>
user = 'https://github.com/blhsing'

bugs.python.org fields:

activity = <Date 2020-01-29.16:25:00.824>
actor = 'cjw296'
assignee = 'none'
closed = True
closed_date = <Date 2019-10-10.14:40:24.310>
closer = 'xtreak'
components = ['Library (Lib)']
creation = <Date 2019-08-28.20:33:01.517>
creator = 'blhsing'
dependencies = []
files = []
hgrepos = []
issue_num = 37972
keywords = ['patch']
message_count = 8.0
messages = ['350688', '351830', '351846', '351877', '351903', '352102', '354383', '360973']
nosy_count = 6.0
nosy_names = ['cjw296', 'michael.foord', 'python-dev', 'mariocj89', 'xtreak', 'blhsing']
pr_nums = ['15565', '15965']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue37972'
versions = ['Python 3.8', 'Python 3.9']

[blhsing]

As reported on StackOverflow:
https://stackoverflow.com/questions/57636747/how-to-perform-assert-has-calls-for-a-getitem-call

The following code would output: [call(), call().foo(), call().foo().__getitem__('bar')]

from unittest.mock import MagicMock, call
mm = MagicMock()
mm().foo()['bar']
print(mm.mock_calls)

but trying to use that list with mm.assert_has_calls([call(), call().foo(), call().foo().__getitem__('bar')]) would result in:

TypeError: tuple indices must be integers or slices, not str

[tirkarthi]

If we go ahead with this then we should also support other dunder methods of tuple like __setitem__ and so on.

[blhsing]

Agreed. I've submitted a new commit with the call chaining behavior now generalized for all dunder methods by delegating the resolution of all attributes not directly in the _Call object's __dict__ keys to the getattr method.

[blhsing]

Correction. I've now done this by delegating the resolution of attributes belonging to the tuple class to _Call.__getattr__ instead. Passed all build tests.

[python-dev]

New changeset 72c3599 by Michael Foord (blhsing) in branch 'master':
bpo-37972: unittest.mock._Call now passes on __getitem__ to the __getattr__ chaining so that call() can be subscriptable (GH-15565)
72c3599

[python-dev]

New changeset db0d8a5 by Michael Foord (Miss Islington (bot)) in branch '3.8':
bpo-37972: unittest.mock._Call now passes on __getitem__ to the __getattr__ chaining so that call() can be subscriptable (GH-15565) (GH-15965)
db0d8a5

[tirkarthi]

Closing as fixed since PRs were merged. Thanks Ben.

[cjw296]

New changeset db5e86a by Chris Withers in branch 'master':
Get mock coverage back to 100% (GH-18228)
db5e86a