unittest ValueError when invoking as module

[BaderSZ]

BPO	46421
Nosy	@rbtcollins, @ezio-melotti, @voidspace, @serhiy-storchaka, @JelleZijlstra, @miss-islington, @kumaraditya303, @BaderSZ
PRs	bpo-46421: Fix unittest filename evaluation when called as a module #30654 [3.10] bpo-46421: Fix unittest filename evaluation when called as a module (GH-30654) #31969 [3.9] bpo-46421: Fix unittest filename evaluation when called as a module (GH-30654) #31970

^{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 2022-03-18.03:25:14.619>
created_at = <Date 2022-01-17.23:35:01.985>
labels = ['type-bug', '3.8', '3.9', '3.10', '3.11', '3.7', 'library']
title = 'unittest ValueError when invoking as module'
updated_at = <Date 2022-03-18.03:25:14.618>
user = 'https://github.com/BaderSZ'

bugs.python.org fields:

activity = <Date 2022-03-18.03:25:14.618>
actor = 'JelleZijlstra'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-18.03:25:14.619>
closer = 'JelleZijlstra'
components = ['Library (Lib)']
creation = <Date 2022-01-17.23:35:01.985>
creator = 'BaderSZ'
dependencies = []
files = []
hgrepos = []
issue_num = 46421
keywords = ['patch']
message_count = 5.0
messages = ['410833', '410834', '415461', '415462', '415468']
nosy_count = 8.0
nosy_names = ['rbcollins', 'ezio.melotti', 'michael.foord', 'serhiy.storchaka', 'JelleZijlstra', 'miss-islington', 'kumaraditya', 'BaderSZ']
pr_nums = ['30654', '31969', '31970']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue46421'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9', 'Python 3.10', 'Python 3.11']

[BaderSZ]

When running a local unittest as a module (for example, python -m unittest ./tests/*.py), the command fails with a ValueError. However, if we remove the local directory definition, and call it as python -m unittest tests/*.py, it runs without issue.

A GitHub pull request with a pull request will be sent promptly.

[BaderSZ]

For reference, this is the error request:

python3 -m unittest ./tests/*.py
Traceback (most recent call last):
  File "/usr/lib64/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib64/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/usr/lib64/python3.10/unittest/__main__.py", line 18, in <module>
    main(module=None)
  File "/usr/lib64/python3.10/unittest/main.py", line 100, in __init__
    self.parseArgs(argv)
  File "/usr/lib64/python3.10/unittest/main.py", line 147, in parseArgs
    self.createTests()
  File "/usr/lib64/python3.10/unittest/main.py", line 158, in createTests
    self.test = self.testLoader.loadTestsFromNames(self.testNames,
  File "/usr/lib64/python3.10/unittest/loader.py", line 220, in loadTestsFromNames
    suites = [self.loadTestsFromName(name, module) for name in names]
  File "/usr/lib64/python3.10/unittest/loader.py", line 220, in <listcomp>
    suites = [self.loadTestsFromName(name, module) for name in names]
  File "/usr/lib64/python3.10/unittest/loader.py", line 154, in loadTestsFromName
    module = __import__(module_name)
ValueError: Empty module name

The issue stems with having "." as its own value in the parts list of unittest/loader.py.

https://github.com/python/cpython/blob/main/Lib/unittest/loader.py#L125