id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
37265	Admin crashes when ModelAdmin.get_action() or get_action_choices() are overridden with their pre-6.1 signatures	Adam Johnson	Adam Johnson	"Django 6.1 crashes with a 500 on every admin page that uses actions (and even during ''system checks'') for projects that override `ModelAdmin.get_action()` or `ModelAdmin.get_action_choices()` with their documented pre-6.1 signatures.

Here’s a minimal reproduction that works on Django 6.0, but crashes on 6.1 and main:

{{{#!python
from django.contrib import admin
from django.db.models import BLANK_CHOICE_DASH

@admin.register(MyModel)
class MyModelAdmin(admin.ModelAdmin):
    actions = [""my_action""]

    # (1) TypeError: get_action() takes 2 positional arguments but 3 were given
    #     Raised by system checks and by any changelist/change form request.
    def get_action(self, action):
        return super().get_action(action)

    # (2) TypeError: get_action_choices() got an unexpected keyword argument 'default_choices'
    def get_action_choices(self, request):
        return super().get_action_choices(request)

    # (2b) Or, with the old default: TypeError: 'NoneType' object is not iterable
    # def get_action_choices(self, request, default_choices=BLANK_CHOICE_DASH):
    #     return [*default_choices, ...]

    @admin.action(description=""My action"")
    def my_action(self, request, queryset):
        ...
}}}

Regression in f30acb184f75fd9260cfd6ddc48a3bbbd49f9c1d (Fixed #12090 -- Added admin actions to the admin change form), interacting with 63c56cda1 (blank-choice default changed to `None`):

* `ModelAdmin._get_base_actions()` now calls `self.get_action(action, action_location)` with two arguments and there is '''no deprecation shim at all''' for old-signature `get_action()` overrides — they raise `TypeError` immediately, including from `ModelAdminChecks._check_actions()`, so `manage.py check` fails too. Overrides returning the old `(callable, name, description)` tuple additionally break downstream `action.name`/`action.func` attribute access on the new `Action` dataclass.
* The `get_action_choices()` shim (`_get_action_choices_with_action_location()`) exists, but always calls `self.get_action_choices(request, default_choices=default_choices)` with `default_choices=None`: overrides without the parameter get an unexpected keyword argument, and overrides keeping the old `default_choices=BLANK_CHOICE_DASH` default receive an explicit `None` instead of their signature default (in 6.0 Django called `get_action_choices(request)` with no extra arguments)."	Bug	assigned	contrib.admin	6.1	Release blocker				Unreviewed	1	0	0	0	0	0