Fixed #32466 -- Corrected autocomplete to_field resolution for complex cases.

In MTI or ForeignKey as primary key cases, it is required to fetch the attname
from the field instance on the remote model in order to reliably resolve the
to_field_name.

Co-authored-by: Johannes Maron <info@johanneshoppe.com>
Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Co-authored-by: Carlton Gibson <carlton.gibson@noumenal.es>

tests/admin_widgets/test_autocomplete_widget.py

@@ -5,7 +5,7 @@ from django.forms import ModelChoiceField
 from django.test import TestCase, override_settings
 from django.utils import translation
 
-from .models import Album, Band
+from .models import Album, Band, ReleaseEvent, VideoStream
 
 
 class AlbumForm(forms.ModelForm):
@@ -41,6 +41,18 @@ class RequiredBandForm(forms.Form):
     )
 
 
+class VideoStreamForm(forms.ModelForm):
+    class Meta:
+        model = VideoStream
+        fields = ['release_event']
+        widgets = {
+            'release_event': AutocompleteSelect(
+                VideoStream._meta.get_field('release_event'),
+                admin.site,
+            ),
+        }
+
+
 @override_settings(ROOT_URLCONF='admin_widgets.urls')
 class AutocompleteMixinTests(TestCase):
     empty_option = '<option value=""></option>'
@@ -114,6 +126,15 @@ class AutocompleteMixinTests(TestCase):
         output = form.as_table()
         self.assertNotIn(self.empty_option, output)
 
+    def test_render_options_fk_as_pk(self):
+        beatles = Band.objects.create(name='The Beatles', style='rock')
+        rubber_soul = Album.objects.create(name='Rubber Soul', band=beatles)
+        release_event = ReleaseEvent.objects.create(name='Test Target', album=rubber_soul)
+        form = VideoStreamForm(initial={'release_event': release_event.pk})
+        output = form.as_table()
+        selected_option = '<option value="%s" selected>Test Target</option>' % release_event.pk
+        self.assertIn(selected_option, output)
+
     def test_media(self):
         rel = Album._meta.get_field('band').remote_field
         base_files = (