Fix DALFRelatedFieldAjax filter repopulation bug

[vigo]

Summary

• Fix filter input not repopulating when selected value is beyond first 20 results (pagination limit)
• Pass selected_text from Python to template, eliminating unnecessary AJAX call
• Gracefully handle deleted/invalid selected values

Fixes #18

Test plan

• Run pytest - all 4 tests pass
• Run pre-commit hooks - all pass
• Manual test with 20+ categories, selecting one beyond first page
• Test with deleted category ID in URL - should not error

🤖 Generated with Claude Code

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (900f40d) to head (38d6bc0).
⚠️ Report is 50 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #21   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
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  Files            3         3           
  Lines           47        54    +7     
=========================================
+ Hits            47        54    +7     

Flag	Coverage Δ
unittests	100.00% <100.00%> (ø)

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[Copilot]

Pull request overview

Fixes DALFRelatedFieldAjax filter UI repopulation by providing the selected option’s display text server-side, avoiding a fragile client-side “first page” lookup.

Changes:

• Add selected_text computation in DALFRelatedFieldAjax and expose it to the template.
• Render selected_text into the AJAX filter template and use it to preselect the Select2 option without an extra AJAX request.
• Add tests covering repopulation and a deleted-selected-value scenario.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

File	Description
tests/testproject/testapp/tests.py	Adds regression tests for selected-text repopulation and deleted-value handling.
src/dalf/templates/admin/filter/django_admin_list_filter_ajax.html	Adds a hidden field to pass selected_text to the frontend.
src/dalf/static/admin/js/django_admin_list_filter.js	Uses selected_text to prepopulate Select2 without an extra AJAX call.
src/dalf/admin.py	Computes selected_text from the related object and includes it in filter template params.

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[Copilot]

On DoesNotExist you set self.selected_value = None, but the query parameter is still present so the changelist remains filtered while the UI shows “All” and the clear button won’t appear (user can get stuck with an un-clearable filter). Instead, keep selected_value and set selected_text to a safe fallback (e.g., the raw ID or a localized “(deleted)” label) so Select2 can render a selected option and allow clearing.

Suggested change

	self.selected_value = None
	# Keep selected_value so the filter state matches the query parameter,
	# but use a safe fallback label so the UI can render and clear it.
	self.selected_text = str(self.selected_value)

[Copilot]

selected_text is derived via a direct related_model.objects.get(pk=...) without going through the admin/autocomplete permission/queryset logic. This can expose the string representation of related objects a user may not have permission to view (and may bypass any admin/queryset restrictions that autocomplete would enforce). Consider resolving the related object via the related model’s registered ModelAdmin (e.g., model_admin.admin_site._registry[related_model]) and its has_view_permission/get_queryset(request) (or fall back to leaving selected_text empty when not permitted).

Suggested change

	try:
	related_model = field.remote_field.model
	obj = related_model.objects.get(pk=self.selected_value)
	self.selected_text = str(obj)
	except (related_model.DoesNotExist, ValueError):
	self.selected_value = None
	related_model = field.remote_field.model
	# Resolve via the related model's ModelAdmin to respect admin permissions
	related_admin = model_admin.admin_site._registry.get(related_model)
	if related_admin is not None:
	qs = related_admin.get_queryset(request)
	try:
	obj = qs.get(pk=self.selected_value)
	except (related_model.DoesNotExist, ValueError):
	# Keep behavior consistent: clear value if object does not exist
	self.selected_value = None
	else:
	if related_admin.has_view_permission(request, obj):
	self.selected_text = str(obj)
	else:
	# User is not allowed to view this object; do not expose its string
	self.selected_text = None
	# If there is no registered ModelAdmin for the related model,
	# we do not attempt a direct objects.get(...) to avoid bypassing permissions.