Fixed #13883 -- Rendered named choice groups with <optgroup> in FilteredSelectMultiple.

This patch adds support for <optgroup>s in FilteredSelectMultiple widgets.
When a popup returns a new object, if the source field contains optgroup
choices, the optgroup is now also included in the response data.

Additionally, this adds error handling for invalid source_model parameters
to prevent crashes and display user-friendly error messages instead.

Co-authored-by: Michael McLarnon <mmclar@gmail.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/tests/admin_views/forms.py b/tests/admin_views/forms.py
index 3a3566c10f..f15a5b3ac1 100644
--- a/tests/admin_views/forms.py
+++ b/tests/admin_views/forms.py
@@ -1,7 +1,10 @@
+from django import forms
 from django.contrib.admin.forms import AdminAuthenticationForm, AdminPasswordChangeForm
 from django.contrib.admin.helpers import ActionForm
 from django.core.exceptions import ValidationError
 
+from .models import Section
+
 
 class CustomAdminAuthenticationForm(AdminAuthenticationForm):
     class Media:
@@ -23,3 +26,63 @@ class CustomAdminPasswordChangeForm(AdminPasswordChangeForm):
 class MediaActionForm(ActionForm):
     class Media:
         js = ["path/to/media.js"]
+
+
+class SectionFormWithOptgroups(forms.ModelForm):
+    articles = forms.ChoiceField(
+        choices=[
+            ("Published", [("1", "Test Article")]),
+            ("Draft", [("2", "Other Article")]),
+        ],
+        required=False,
+    )
+
+    class Meta:
+        model = Section
+        fields = ["name", "articles"]
+
+
+class SectionFormWithObjectOptgroups(forms.ModelForm):
+    """Form with model instances as optgroup keys (tests str() conversion)."""
+
+    articles = forms.ChoiceField(required=False)
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        # Use Section instances as optgroup keys
+        sections = Section.objects.all()[:2]
+        if sections:
+            self.fields["articles"].choices = [
+                (sections[0], [("1", "Article 1")]),
+                (
+                    sections[1] if len(sections) > 1 else sections[0],
+                    [("2", "Article 2")],
+                ),
+            ]
+
+    class Meta:
+        model = Section
+        fields = ["name", "articles"]
+
+
+class SectionFormWithDynamicOptgroups(forms.ModelForm):
+    """
+    Form where the field with optgroups is added dynamically in __init__.
+    This tests that the implementation doesn't rely on accessing the
+    uninstantiated form class's _meta or fields, which wouldn't work here.
+    """
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        # Dynamically add a field with optgroups after instantiation.
+        self.fields["articles"] = forms.ChoiceField(
+            choices=[
+                ("Category A", [("1", "Item 1"), ("2", "Item 2")]),
+                ("Category B", [("3", "Item 3"), ("4", "Item 4")]),
+            ],
+            required=False,
+        )
+
+    class Meta:
+        model = Section
+        fields = ["name"]