[3.2.x] 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.

Backport of ceb4b9ee68 from main Backport of 03d0f12c82 from main

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/models.py

@@ -18,7 +18,11 @@ class Member(models.Model):
         return self.name
 
 
-class Band(models.Model):
+class Artist(models.Model):
+    pass
+
+
+class Band(Artist):
     uuid = models.UUIDField(unique=True, default=uuid.uuid4)
     name = models.CharField(max_length=100)
     style = models.CharField(max_length=20)
@@ -47,6 +51,25 @@ class Album(models.Model):
         return self.name
 
 
+class ReleaseEvent(models.Model):
+    """
+    Used to check that autocomplete widget correctly resolves attname for FK as
+    PK example.
+    """
+    album = models.ForeignKey(Album, models.CASCADE, primary_key=True)
+    name = models.CharField(max_length=100)
+
+    class Meta:
+        ordering = ['name']
+
+    def __str__(self):
+        return self.name
+
+
+class VideoStream(models.Model):
+    release_event = models.ForeignKey(ReleaseEvent, models.CASCADE)
+
+
 class HiddenInventoryManager(models.Manager):
     def get_queryset(self):
         return super().get_queryset().filter(hidden=False)

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 = (

tests/admin_widgets/tests.py

@@ -24,7 +24,7 @@ from django.utils import translation
 from .models import (
     Advisor, Album, Band, Bee, Car, Company, Event, Honeycomb, Individual,
     Inventory, Member, MyFileField, Profile, School, Student,
-    UnsafeLimitChoicesTo,
+    UnsafeLimitChoicesTo, VideoStream,
 )
 from .widgetadmin import site as widget_admin_site
 
@@ -624,7 +624,17 @@ class ForeignKeyRawIdWidgetTest(TestCase):
         self.assertHTMLEqual(
             w.render('test', None),
             '<input type="text" name="test" class="vForeignKeyRawIdAdminField">\n'
-            '<a href="/admin_widgets/band/?name=%22%26%3E%3Cescapeme&amp;_to_field=id" '
+            '<a href="/admin_widgets/band/?name=%22%26%3E%3Cescapeme&amp;_to_field=artist_ptr" '
+            'class="related-lookup" id="lookup_id_test" title="Lookup"></a>'
+        )
+
+    def test_render_fk_as_pk_model(self):
+        rel = VideoStream._meta.get_field('release_event').remote_field
+        w = widgets.ForeignKeyRawIdWidget(rel, widget_admin_site)
+        self.assertHTMLEqual(
+            w.render('test', None),
+            '<input type="text" name="test" class="vForeignKeyRawIdAdminField">\n'
+            '<a href="/admin_widgets/releaseevent/?_to_field=album" '
             'class="related-lookup" id="lookup_id_test" title="Lookup"></a>'
         )
 

tests/admin_widgets/widgetadmin.py

@@ -2,7 +2,7 @@ from django.contrib import admin
 
 from .models import (
     Advisor, Album, Band, Bee, Car, CarTire, Event, Inventory, Member, Profile,
-    School, User,
+    ReleaseEvent, School, User, VideoStream,
 )
 
 
@@ -47,6 +47,8 @@ site.register(Member)
 site.register(Band)
 site.register(Event, EventAdmin)
 site.register(Album, AlbumAdmin)
+site.register(ReleaseEvent, search_fields=['name'])
+site.register(VideoStream, autocomplete_fields=['release_event'])
 
 site.register(Inventory)