[6.0.x] Fixed #36949 -- Improved RelatedFieldWidgetWrapper <label>s.

Regression in 4187da258fe212d494cb578a0bc2b52c4979ab95.

Backport of 253f552c5809fa096116b601bd842ca4f3504860 from main.

4 files changed, 68 insertions, 2 deletions

diff --git a/django/contrib/admin/widgets.py b/django/contrib/admin/widgets.py
index f5c3939012..1dfac1b323 100644
--- a/django/contrib/admin/widgets.py
+++ b/django/contrib/admin/widgets.py
@@ -28,6 +28,8 @@ class FilteredSelectMultiple(forms.SelectMultiple):
     catalog has been loaded in the page
     """
 
+    use_fieldset = True
+
     class Media:
         js = [
             "admin/js/core.js",
@@ -300,7 +302,7 @@ class RelatedFieldWidgetWrapper(forms.Widget):
         self.can_view_related = supported and can_view_related
         # To check if the related object is registered with this AdminSite.
         self.admin_site = admin_site
-        self.use_fieldset = True
+        self.use_fieldset = widget.use_fieldset
 
     def __deepcopy__(self, memo):
         obj = copy.copy(self)
diff --git a/docs/releases/6.0.4.txt b/docs/releases/6.0.4.txt
index e24397d9bc..1967edacc8 100644
--- a/docs/releases/6.0.4.txt
+++ b/docs/releases/6.0.4.txt
@@ -14,3 +14,7 @@ Bugfixes
   and :func:`~django.contrib.auth.alogout` did not respectively set or clear
   ``request.user`` if it had already been materialized (e.g., by sync
   middleware) (:ticket:`37017`).
+
+* Fixed a regression in Django 6.0 in admin forms where
+  ``RelatedFieldWidgetWrapper`` incorrectly wrapped all widgets in a
+  ``<fieldset>`` (:ticket:`36949`).
diff --git a/tests/admin_views/tests.py b/tests/admin_views/tests.py
index 203e1d25a9..f766794c54 100644
--- a/tests/admin_views/tests.py
+++ b/tests/admin_views/tests.py
@@ -6922,17 +6922,28 @@ class SeleniumTests(AdminSeleniumTestCase):
             "Difficulty:",
             "Materials:",
             "Start datetime:",
-            "Categories:",
         ]
         url = reverse("admin:admin_views_course_change", args=(course.pk,))
         self.selenium.get(self.live_server_url + url)
         fieldsets = self.selenium.find_elements(
             By.CSS_SELECTOR, "fieldset.aligned fieldset"
         )
+        self.assertEqual(len(fieldsets), len(expected_legend_tags_text))
         for index, fieldset in enumerate(fieldsets):
             legend = fieldset.find_element(By.TAG_NAME, "legend")
             self.assertEqual(legend.text, expected_legend_tags_text[index])
 
+        # FilteredSelectMultiple uses <fieldset>.
+        url = reverse("admin:admin_views_camelcaserelatedmodel_add")
+        self.selenium.get(self.live_server_url + url)
+        fieldsets = self.selenium.find_elements(
+            By.CSS_SELECTOR, "fieldset.aligned fieldset"
+        )
+        self.assertEqual(len(fieldsets), 1)
+        for index, fieldset in enumerate(fieldsets):
+            legend = fieldset.find_element(By.TAG_NAME, "legend")
+            self.assertEqual(legend.text, "M2m:")
+
     @screenshot_cases(["desktop_size", "mobile_size", "rtl", "dark", "high_contrast"])
     def test_use_fieldset_with_grouped_fields(self):
         from selenium.webdriver.common.by import By
diff --git a/tests/modeladmin/tests.py b/tests/modeladmin/tests.py
index 4a92514e17..c1c8b52346 100644
--- a/tests/modeladmin/tests.py
+++ b/tests/modeladmin/tests.py
@@ -830,6 +830,55 @@ class ModelAdminTests(TestCase):
             ["extra", "transport", "id", "DELETE", "main_band"],
         )
 
+    def test_foreign_key_as_custom_widget(self):
+        class CustomSelectMultiple(forms.SelectMultiple):
+            def build_attrs(self, base_attrs, extra_attrs=None):
+                attrs = super().build_attrs(base_attrs, extra_attrs)
+                attrs["data-custom-widget"] = "true"
+                return attrs
+
+        class ConcertAdmin(ModelAdmin):
+            formfield_overrides = {
+                models.ForeignKey: {"widget": CustomSelectMultiple},
+            }
+
+        cma = ConcertAdmin(Concert, self.site)
+        cmafa = cma.get_form(request)
+        expected = (
+            '<div><label for="id_main_band">Main band:</label><div '
+            'class="related-widget-wrapper" data-model-ref="band"><select '
+            'name="main_band" data-context="available-source" required '
+            'id="id_main_band" data-custom-widget="true" multiple>'
+            '<option value="">---------</option><option value="1">The Doors</option>'
+            "</select></div></div>"
+        )
+        self.assertInHTML(expected, cmafa().render())
+
+    def test_foreign_key_as_custom_widget_with_fieldset(self):
+        class CustomSelectMultipleFieldset(forms.RadioSelect):
+            use_fieldset = True
+
+            def build_attrs(self, base_attrs, extra_attrs=None):
+                attrs = super().build_attrs(base_attrs, extra_attrs)
+                attrs["use_fieldset"] = "true"
+                return attrs
+
+        class ConcertAdmin(ModelAdmin):
+            formfield_overrides = {
+                models.ForeignKey: {"widget": CustomSelectMultipleFieldset},
+            }
+
+        cma = ConcertAdmin(Concert, self.site)
+        cmafa = cma.get_form(request)
+        expected = (
+            '<fieldset><legend>Main band:</legend><div class="related-widget-wrapper" '
+            'data-model-ref="band"><div id="id_main_band"><div><label '
+            'for="id_main_band_0"><input type="radio" name="main_band" value="1" '
+            'data-context="available-source" required id="id_main_band_0" '
+            'use_fieldset="true">The Doors</label></div></div></div></fieldset>'
+        )
+        self.assertInHTML(expected, cmafa().render())
+
     def test_log_actions(self):
         ma = ModelAdmin(Band, self.site)
         mock_request = MockRequest()