Retain filter params in ModelAdmin's search form

This basically uses the same code as django uses for the search form in
its ModelAdmin, to retain the current query params (template
admin/search_form.html).

Fixes #6006

CHANGELOG.txt

@@ -29,6 +29,7 @@ Changelog
  * Fix: Ensure that disabled buttons have a consistent presentation on hover to indicate no interaction is available (Paarth Agarwal)
  * Fix: Update the 'Locked pages' report menu title so that it is consistent with other pages reports and its own title on viewing (Nicholas Johnson)
  * Fix: Support `formfield_callback` handling on `ModelForm.Meta` for future Django 4.2 release (Matt Westcott)
+ * Fix: Ensure that `ModelAdmin` correctly supports filters in combination with subsequent searches without clearing the applied filters (Stefan Hammer)
 
 
 4.0.2 (xx.xx.xxxx) - IN DEVELOPMENT

docs/releases/4.1.md

@@ -41,6 +41,7 @@ Wagtail 4.1 is designated a Long Term Support (LTS) release. Long Term Support r
  * Ensure that disabled buttons have a consistent presentation on hover to indicate no interaction is available (Paarth Agarwal)
  * Update the 'Locked pages' report menu title so that it is consistent with other pages reports and its own title on viewing (Nicholas Johnson)
  * Support `formfield_callback` handling on `ModelForm.Meta` for future Django 4.2 release (Matt Westcott)
+ * Ensure that `ModelAdmin` correctly supports filters in combination with subsequent searches without clearing the applied filters (Stefan Hammer)
 
 ## Upgrade considerations
 

wagtail/contrib/modeladmin/templates/modeladmin/includes/search_form.html

@@ -6,5 +6,9 @@
             <input id="id_q" name="{{ search_var }}" value="{{ view.query }}" placeholder="{% blocktrans trimmed with view.verbose_name_plural|lower as name %}Search {{ name }}{% endblocktrans %}" type="text">
         {% endfield %}
         <button type="submit" class="w-sr-only">{% trans 'Search' %}</button>
+        {# Keep all parameters from the query string (e.g. filter state). #}
+        {% for name, value in view.params.items %}
+            {% if name != search_var %}<input type="hidden" name="{{ name }}" value="{{ value }}">{% endif %}
+        {% endfor %}
     </form>
 {% endif %}

wagtail/contrib/modeladmin/tests/test_simple_modeladmin.py

@@ -156,6 +156,13 @@ class TestBookIndexView(TestCase, WagtailTestUtils):
             response, '<span class="result-count">2 out of 4</span>', html=True
         )
 
+        # The search form should retain the filter
+        self.assertContains(
+            response,
+            '<input type="hidden" name="author__id__exact" value="1">',
+            html=True,
+        )
+
         for book in response.context["object_list"]:
             self.assertEqual(book.author_id, 1)