fix: filtered choices get lost when search used after filtering

[sezginacer]

What version of Unfold are you using?

main

What version of Django are you using?

5.1

What browser are you using?

Firefox 135.0

Did you checked changelog/commit history, if the bug is not already fixed?

Yes

Did you searched other issues, if the bug is not already fixed?

Yes

Did you checked documentation?

Yes

Are you able to replicate the bug in the demo site?

No, I could not find MultipleDropdownFilter or MultipleRelatedDropdownFilter on demo site.

Repository with reproduced bug

No

Describe your issue

Suppose we have an admin class like below.

@admin.register(SampleModel)
class SampleModelAdmin(ModelAdmin):
    list_filter = [
        ("status", MultipleDropdownFilter), 
        ("owner", MultipleRelatedDropdownFilter),
        ("writer", MultipleRelatedDropdownFilter),
    ]

• Go to change_list page.
• Choose some filters and apply. Then let's say, current URL after filtering is /admin/app/model/?status=open&status=closed&owner__id__exact=1&owner__id__exact=2&owner__id__exact=3&writer__id__exact=5
• Write 'test' to search form & click enter. Current URL after search is /admin/app/model/?q=test&status=open&owner__id__exact=1&writer__id__exact=5
• So, status=closed and owner__id__exact=2&owner__id__exact=3 filters get lost.

While just filtering (not searching), there is no problem like this one. But filter a field with multiple values then searching breaks query string & filters.

[lukasvinclav]

Would you mind to test again on the most recent version of main?

[sezginacer]

When I installed the latest version (0.47.0), nothing has changed, the problem stays the same.

[sezginacer]

I have recently opened a PR for this issue

[lukasvinclav]

That PR helped me to debug the issue. Already merged so you can test directly on main. Thanks again

[dbartenstein]

@sezginacer unfortunately the merged PR #1042 (comment) breaks compatibility with Django 4.2 LTS (supported until April 2026).

I understand the issue you were facing with multiple values for the same parameter name.

• Unfortunately, in Django 4.2’s ChangeList there’s no filter_params, but only params, which swallows multiple values: https://github.com/django/django/blob/stable/4.2.x/django/contrib/admin/views/main.py#L112

• In Django 5.x’s ChangeList there’s filter_params: https://github.com/django/django/blob/240421c7c4c81fe5df26274b807266bd4ca73d7f/django/contrib/admin/views/main.py#L128

Options

• One option is to restore functionality for Django 4.2 with a fallback to params if filter_params is unavailable. But that will only restore the previous behavior for Django 4.2 without support for multiple values.
• Alternatively, we could introduce ChangeList for unfold and add filter_params which either falls back to the super classes filter_params or the backported code for Django 4.2.
• Do you have other ideas? E.g. is there a better way of providing multiple values for the same param? ?status=2&status=3 ain’t best practise.

[sezginacer]

Sorry for inconvenience. ModelAdmin.get_changelist_instance can be overridden easily. So, I think custom ChangeList class is the best solution among those mentioned.

[dbartenstein]

Sorry for inconvenience. ModelAdmin.get_changelist_instance can be overridden easily. So, I think custom ChangeList class is the best solution among those mentioned.

No worries @sezginacer - thanks for your fix!

@lukasvinclav are you also fine with a custom ChangeList class?

[sezginacer]

if @lukasvinclav OK with the custom ChangeList class, I can create a PR for the fix.

[lukasvinclav]

@dbartenstein @sezginacer please draft new PR with the changelist implementation