[Django] #36942: SimpleTestCase._remove_databases_failures() is not idempotent and crashes on complex MRO.

[Django]

#36942: SimpleTestCase._remove_databases_failures() is not idempotent and crashes
on complex MRO.
---------------------------------------------+-----------------------------
Reporter: Michele0303 | Owner: michele0303
Type: Bug | Status: assigned
Component: Testing framework | Version: 6.0
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 1
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
---------------------------------------------+-----------------------------
When using complex test inheritance (e.g., mixing multiple
LiveServerTestCase subclasses or dynamic test class generation), the
cleanup method
{{{_remove_databases_failures}}} can be called in a state where database
connection methods have already been unwrapped or were never wrapped for a
specific alias.

Currently, the code assumes the wrapped attribute always exists:
{{{setattr(connection, name, method.wrapped)}}}

This leads to an {{{AttributeError: 'function' object has no attribute
'wrapped'.}}}

The proposed fix adds a defensive {{{hasattr(method, "wrapped")}}} check
to make the teardown process idempotent and robust against complex class
hierarchies.
--
Ticket URL: <https://code.djangoproject.com/ticket/36942>
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[Django]

#36942: SimpleTestCase._remove_databases_failures() is not idempotent and crashes
on complex MRO.

-----------------------------------+---------------------------------------
Reporter: Michele Fiori | Owner: michele0303

Type: Bug | Status: assigned
Component: Testing framework | Version: 6.0

Severity: Normal | Resolution:

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 Michele Fiori):

* Attachment "check_mro.py" added.

[Django]

#36942: SimpleTestCase._remove_databases_failures() is not idempotent and crashes
on complex MRO.
-----------------------------------+---------------------------------------
Reporter: Michele Fiori | Owner: michele0303
Type: Bug | Status: assigned
Component: Testing framework | Version: 6.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-----------------------------------+---------------------------------------

Description changed by Michele Fiori:

Old description:

> When using complex test inheritance (e.g., mixing multiple
> LiveServerTestCase subclasses or dynamic test class generation), the
> cleanup method
> {{{_remove_databases_failures}}} can be called in a state where database
> connection methods have already been unwrapped or were never wrapped for
> a specific alias.
>
> Currently, the code assumes the wrapped attribute always exists:
> {{{setattr(connection, name, method.wrapped)}}}
>
> This leads to an {{{AttributeError: 'function' object has no attribute
> 'wrapped'.}}}
>
> The proposed fix adds a defensive {{{hasattr(method, "wrapped")}}} check
> to make the teardown process idempotent and robust against complex class
> hierarchies.

New description:

When using complex test inheritance (e.g., mixing multiple
LiveServerTestCase subclasses or dynamic test class generation), the
cleanup method
{{{_remove_databases_failures}}} can be called in a state where database
connection methods have already been unwrapped or were never wrapped for a
specific alias.

Currently, the code assumes the wrapped attribute always exists:
{{{setattr(connection, name, method.wrapped)}}}

This leads to an {{{AttributeError: 'function' object has no attribute
'wrapped'.}}}

The proposed fix adds a defensive {{{hasattr(method, "wrapped")}}} check
to make the teardown process idempotent and robust against complex class
hierarchies.

PR: https://github.com/django/django/pull/20758

--
--
Ticket URL: <https://code.djangoproject.com/ticket/36942#comment:1>

[Django]

#36942: SimpleTestCase._remove_databases_failures() is not idempotent and crashes
on complex MRO.
-----------------------------------+---------------------------------------
Reporter: Michele Fiori | Owner: michele0303

Type: Bug | Status: closed

Component: Testing framework | Version: 6.0

Severity: Normal | Resolution: needsinfo

Keywords: | Triage Stage: Unreviewed
Has patch: 1 | Needs documentation: 0

Needs tests: 1 | Patch needs improvement: 0

Easy pickings: 0 | UI/UX: 0
-----------------------------------+---------------------------------------

Changes (by Jacob Walls):

* needs_tests: 0 => 1
* resolution: => needsinfo
* status: assigned => closed

Comment:

Hi Michele,

Thanks for the report. Seems reasonable, but without a example to play
with it's a little hard to QA it. Could you provide an example class
hierarchy that produces the issue? Happy to take another look then.
--
Ticket URL: <https://code.djangoproject.com/ticket/36942#comment:2>