unittest: _top_level_dir is incorrectly persisted between calls to different load_test methods

[bitdancer]

BPO	15010
Nosy	@bitdancer, @voidspace, @ZackerySpytz
PRs	gh-59215: unittest: _top_level_dir is incorrectly persisted #15242
Files	restore_top_level_dir.patch restore_top_level_dir_to_previous_value.patch

^{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 2012-06-06.01:20:42.735>
labels = ['type-bug', 'library', '3.9', '3.10', '3.11']
title = 'unittest: _top_level_dir is incorrectly persisted between calls to different load_test methods'
updated_at = <Date 2021-11-27.11:54:46.946>
user = 'https://github.com/bitdancer'

bugs.python.org fields:

activity = <Date 2021-11-27.11:54:46.946>
actor = 'iritkatriel'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2012-06-06.01:20:42.735>
creator = 'r.david.murray'
dependencies = []
files = ['26442', '26458']
hgrepos = []
issue_num = 15010
keywords = ['patch']
message_count = 5.0
messages = ['162387', '165887', '165954', '165966', '348649']
nosy_count = 4.0
nosy_names = ['r.david.murray', 'michael.foord', 'igorsobreira', 'ZackerySpytz']
pr_nums = ['15242']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue15010'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

Linked PRs

• [3.12] gh-59215: unittest: restore _top_level_dir at end of discovery (GH-15242) #117508
• [3.11] gh-59215: unittest: restore _top_level_dir at end of discovery (GH-15242) #117509

[bitdancer]

During the execution of the load tests protocol, the loader instance will set its _top_level_dir attribute, and this will persist if the loader is passed on to another load_tests method. If that method does not specify a top_level_dir in a discovery call, the wrong top_level_dir may be used, and loading will fail.

You can reproduce this by having two test *packages* with a load_tests method that calls discover in their __init__.py, and specify both package names to the unittest CLI.

[igorsobreira]

Hello. I've attached a patch to cleanup self._top_level_dir in the end of discover(). Is that the expected behavior or I'm on the wrong track?

[igorsobreira]

My previous patch is incorrect, talking to voidspace on irc self._top_leve_dir should be reverted to it's previous value

"so when discover is called the original value should be stored, then discovery done, and then the original restored"

I'll work on this one.

He also pointed out that this bugfix should be backported to 2.7 and 3.2

[igorsobreira]

Updated patch to restore previous value of ._top_level_dir on discover() done. And added a unit test.

[vstinner]

This issue is not newcomer friendly, I remove the easy keyword.