pytest 5.4 skips Django's teardown (causing e.g. "connection already closed" errors)

[Fak3]

pytest-django==3.5.1
django versions tested: 2.2.11 and 3.0.4

When one test fails, all tests which use database launched after this test will fail with traceback:

test/apiv2/put_inputevent__test.py:34: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/model_mommy/mommy.py:54: in make
    return mommy.make(_save_kwargs=_save_kwargs, **attrs)
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/model_mommy/mommy.py:228: in make
    return self._make(commit=True, commit_related=True, _save_kwargs=_save_kwargs, **attrs)
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/model_mommy/mommy.py:265: in _make
    instance = self.instance(self.model_attrs, _commit=commit, _save_kwargs=_save_kwargs)
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/model_mommy/mommy.py:289: in instance
    instance.save(**_save_kwargs)
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/models/base.py:741: in save
    force_update=force_update, update_fields=update_fields)
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/models/base.py:779: in save_base
    force_update, using, update_fields,
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/models/base.py:851: in _save_table
    forced_update)
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/models/base.py:900: in _do_update
    return filtered._update(values) > 0
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/models/query.py:760: in _update
    return query.get_compiler(self.db).execute_sql(CURSOR)
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/models/sql/compiler.py:1469: in execute_sql
    cursor = super().execute_sql(result_type)
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/models/sql/compiler.py:1138: in execute_sql
    cursor = self.connection.cursor()
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/backends/base/base.py:256: in cursor
    return self._cursor()
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/backends/base/base.py:235: in _cursor
    return self._prepare_cursor(self.create_cursor(name))
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/utils.py:89: in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/backends/base/base.py:235: in _cursor
    return self._prepare_cursor(self.create_cursor(name))
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <django.db.backends.postgresql.base.DatabaseWrapper object at 0x7fe8150ed208>, name = None

    def create_cursor(self, name=None):
        if name:
            # In autocommit mode, the cursor will be used outside of a
            # transaction, hence use a holdable cursor.
            cursor = self.connection.cursor(name, scrollable=False, withhold=self.connection.autocommit)
        else:
>           cursor = self.connection.cursor()
E           django.db.utils.InterfaceError: connection already closed

/home/u1/.virtualenvs/npserver/lib/python3.7/site-packages/django/db/backends/postgresql/base.py:223: InterfaceError

Downgrading to pytest==5.3.5 fixes the issue.

Not yet sure if this is pytest issue or pytest-django.

[bluetech]

Can you confirm this happens also on pytest 5.4.1?

If yes, then a minimal reproduction would be great.

[Fak3]

Yes, 5.4.1 too. Will try to create minimal case.

[Fak3]

Created minimal django project: https://github.com/Fak3/testproject-824-git

[bluetech]

Thanks for the reproduction!

It looked to me like a problem in pytest's unittest support, so I looked at changes made to that in pytest in 5.4.x. Reverting pytest-dev/pytest#5996 "unittest: do not use TestCase.debug() with --pdb" (and other commits in that PR) fixes the problem.

cc @blueyed @nicoddemus who worked on that PR and probably have a better idea than me.

[blueyed]

@Fak3
Please try #825.
The problem is that Django's (rather custom) teardown gets not called (because this is throwing an exception to get out of unittest's __call__, so that --pdb can be used before any teardown - although you could also just add a pdb.set_tracce() and be done).

(It's the next round of the long-standing issue from 2016, and I still think it should have been reverted first at least instead (ref pytest-dev/pytest#6014), until it gets done properly, e.g. via something like blueyed/pytest#107))

pytest-django could intercept Django's _post_teardown (https://github.com/django/django/blob/1a09708dcb2f60ad5ca0a75b8de9619356f74ff6/django/test/testcases.py#L274), and do it after the call, but that would still require to first patch pytest to not use the current approach.

[Fak3]

Please try #825.

Yes, that PR fixes this issue