#37064: SimpleTestCase._remove_databases_failures() crashes on un-wrapped
connection methods
-----------------------------------+--------------------------------------
Reporter: Rio Weber | Owner: (none)
Type: Bug | Status: closed
Component: Testing framework | Version: 6.0
Severity: Normal | Resolution: invalid
Keywords: | Triage Stage: Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-----------------------------------+--------------------------------------
Changes (by Natalia Bidart):
* keywords: testcase, databases, multi-db, regression =>
* resolution: => invalid
* status: new => closed
Comment:
The premise of this ticket is that `_remove_databases_failures` should be
defensive about state it itself established. That framing inverts the
actual contract.
`_add_databases_failures` and `_remove_databases_failures` are a symmetric
setup/teardown pair. The setup installs a `_DatabaseFailure` wrapper on
each disallowed connection method, the teardown removes it. The teardown's
assumption that `.wrapped` exists **is not a fragility**: it is a direct
consequence of the setup having run. If that attribute is missing,
something replaced Django's wrapper without restoring the original, which
is a bug ''in that code, not in Django''.
The submitted PR confirm this. The test validates the case where a method
has been swapped out from under Django without a proper restore, therefore
proving the bug exists in the code doing the swapping, then asks Django to
silently accommodate it. The proposed `isinstance` guard also makes
teardown silently incomplete: if the invariant is broken, the original
method is never restored. The connection is left in whatever unknown state
the third-party code deposited. That failure mode is harder to debug than
the current `AttributeError`, which at least points clearly at the code
that broke the invariant.
Closing as invalid. If a reproduction can be demonstrated with no third-
party connection wrapping involved, and not connection mutation without
proper restore, please reopen with a self-contained test case against a
clean Django install.
--
Ticket URL: <https://code.djangoproject.com/ticket/37064#comment:23>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion visit
https://groups.google.com/d/msgid/django-updates/0107019dc74dbe46-80b3173d-60fb-4fa9-a548-df8c08985538-000000%40eu-central-1.amazonses.com.
