Windows: Running the Python test suite sequentially is interrupted by (Pdb) prompt

[shreyanavigyan]

BPO	43955
Nosy	@gvanrossum, @tim-one, @pfmoore, @vstinner, @tjguk, @markshannon, @zware, @serhiy-storchaka, @zooba, @gvanrossum, @corona10, @shihai1991, @shreyanavigyan
PRs	bpo-43955: Handle the case where the distutils warning has already been triggered #25675
Files	tests_log.txt: Full Error Log

^{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 2021-04-28.15:27:25.688>
created_at = <Date 2021-04-27.17:03:07.285>
labels = ['3.10', 'OS-windows']
title = 'Windows: Running the Python test suite sequentially is interrupted by (Pdb) prompt'
updated_at = <Date 2021-04-28.15:27:25.687>
user = 'https://github.com/shreyanavigyan'

bugs.python.org fields:

activity = <Date 2021-04-28.15:27:25.687>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2021-04-28.15:27:25.688>
closer = 'vstinner'
components = ['Windows']
creation = <Date 2021-04-27.17:03:07.285>
creator = 'shreyanavigyan'
dependencies = []
files = ['49995']
hgrepos = []
issue_num = 43955
keywords = ['patch']
message_count = 29.0
messages = ['392104', '392109', '392114', '392117', '392118', '392119', '392120', '392121', '392132', '392133', '392134', '392135', '392136', '392139', '392140', '392141', '392149', '392150', '392154', '392164', '392182', '392189', '392190', '392194', '392196', '392214', '392216', '392218', '392219']
nosy_count = 13.0
nosy_names = ['gvanrossum', 'tim.peters', 'paul.moore', 'vstinner', 'tim.golden', 'Mark.Shannon', 'zach.ware', 'serhiy.storchaka', 'steve.dower', 'Guido.van.Rossum', 'corona10', 'shihai1991', 'shreyanavigyan']
pr_nums = ['25675']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue43955'
versions = ['Python 3.10']

[shreyanavigyan]

Recent test failures have been noticed on Windows 10. The full test log has been attached. The tests test_distutils, test_pdb, test_signal and test_threading require a little bit of attention since there seems to be some kind of error.

[gvanrossum]

I wonder if these four tests do something that affects all threads? The test driver module runs tests in parallel (if you ask it to run all or most tests, like the default).

[shreyanavigyan]

Pdb error source -

cpython/Lib/test/test_pdb.py

Line 1270 in 9aea31d

def test_pdb_issue_20766():

This is where the error in Pdb is originating from.

[shreyanavigyan]

The test expects the <built-in default_int_handler> but gets sigint_handler method of a pdb.Pdb instance instead.

[gvanrossum]

Can you submit a PR that fixes it?

[tim-one]

I expect parallelism is a red herring: early in the test output attached to this report:

0:00:04 Run tests sequentially

and there's no other evidence in the output that multiple tests are running simultaneously.

Also on Win10, the 4 failing tests here pass for me if I run them one at a time, so it's not obvious.

I _suspect_ that what's going wrong with test_pdb is the root cause: every now & again, for some weeks now, when I try to run tests on Windows I come back to the cmd.exe window and see that it's just sitting there, waiting at a pdb prompt.

In the output attached to this report, note that after test_threading starts,

(Pdb) continue
(Pdb) continue
(Pdb) continue
(Pdb) continue

appears out of the blue. But test_pdb is long finished by that time.

But I'm clueless about current pdb internals.

[shreyanavigyan]

Yes you're right. Running the failed tests individually does not trigger the errors. And the

(Pdb) continue
(Pdb) continue
(Pdb) continue
(Pdb) continue

actually is manually entered by me. My tests also stop at that prompt but somehow entering these commands again allow us to continue. Why are the errors triggering at all? The tests that are failing when ran alongside the test suite haven't been messed with for a very long time now and still somehow out of the blue they are failing. Any thoughts?

[gvanrossum]

Yes, I also see that pdb prompt. I recommend looking at what different
configurations are used by test.libregrtest.main() when no tests are passed
on the command line.

[vstinner]

File "C:\github\cpython\lib\test\test_distutils.py", line 15, in <module>
import distutils.tests
File "C:\github\cpython\lib\contextlib.py", line 140, in __exit__
next(self.gen)
File "C:\github\cpython\lib\test\support\warnings_helper.py", line 179, in _filterwarnings
raise AssertionError("filter (%r, %s) did not catch any warning" %
AssertionError: filter ('The distutils package is deprecated', DeprecationWarning) did not catch any warning

Ah, test_distutils fails if distutils was already imported previously. The test should be fixed.

"""
test test_pdb failed -- Traceback (most recent call last):
  File "C:\github\cpython\lib\doctest.py", line 2205, in runTest
    raise self.failureException(self.format_failure(new.getvalue()))
AssertionError: Failed doctest test for test.test_pdb.test_pdb_issue_20766
  File "C:\github\cpython\lib\test\test_pdb.py", line 1270, in test_pdb_issue_20766
"""

This is a surprising failure. No clue why test_pdb fails when other tests are run previously (when tests are run sequentially).

See also bpo-43960

[vstinner]

Shreyan Avigyan:

And the "(Pdb) continue (...) actually is manually entered by me.

Do you mean that you modified the Python source code? Does the issue go away if you revert your change or if you test a newly installed Python?

[zooba]

I think the test failures cascade, and some state is not being cleaned up. I'm trying to work through them now, but if someone else is as well, do say so and I'll find something else to do.