unittest.patch confuses modules with base modules

[twolodzko]

BPO	42535
Nosy	@tirkarthi, @twolodzko, @akulakov

^{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 = None
created_at = <Date 2020-12-02.11:14:10.667>
labels = ['3.7', 'type-bug', 'library']
title = 'unittest.patch confuses modules with base modules'
updated_at = <Date 2021-07-17.14:15:49.350>
user = 'https://github.com/twolodzko'

bugs.python.org fields:

activity = <Date 2021-07-17.14:15:49.350>
actor = 'andrei.avk'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-12-02.11:14:10.667>
creator = 'twolodzko'
dependencies = []
files = []
hgrepos = []
issue_num = 42535
keywords = []
message_count = 2.0
messages = ['382303', '397723']
nosy_count = 3.0
nosy_names = ['xtreak', 'twolodzko', 'andrei.avk']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42535'
versions = ['Python 3.7']

[twolodzko]

Nonetheless having several attempts, I wasn't able to create reproducible example for this bug, but I will try describing it in detail.

I have a package with multiple modules. One of the paths is like mymodule.nestedmodule.io, among other functions, this module contains functions foo() and bar(), where bar() does call foo(). The module does not import base python's io module. I have a unit test that patches:

with path('mymodule.nestedmodule.io.foo'):
    bar()

The problem is, when running the test I get the following error: AttributeError: <module 'io' from '/usr/local/lib/python3.7/io.py'> does not have the attribute 'foo'. The problem is solved when I rename io to myio and correct all the paths to use the new name.

[akulakov]

I've tested this in both 3.7.7 and 3.9.1 and could not reproduce.