Refs #31262 -- Delegated RelatedFieldWidgetWrapper._choices handling …

…to wrapped widget.

``ModelChoiceField`` uses ``_choices`` to avoid extra queries being
triggered and, as such, we need to pass through manipulation of this
to the underlying widget if we want to alter ``_choices`` to prevent
re-normalization.

django/contrib/admin/widgets.py

@@ -302,6 +302,14 @@ def choices(self):
     def choices(self, value):
         self.widget.choices = value
 
+    @property
+    def _choices(self):
+        return self.widget._choices
+
+    @_choices.setter
+    def _choices(self, value):
+        self.widget._choices = value
+
     def get_related_url(self, info, action, *args):
         return reverse(
             "admin:%s_%s_%s" % (info + (action,)),

django/forms/fields.py

@@ -885,8 +885,8 @@ def choices(self):
     @choices.setter
     def choices(self, value):
         # Setting choices on the field also sets the choices on the widget.
-        # Note that the property setter for the widget will re-normalize.
-        self._choices = self.widget.choices = normalize_field_choices(value)
+        # Note that we bypass the property setter to avoid re-normalizing.
+        self._choices = self.widget._choices = normalize_field_choices(value)
 
     def to_python(self, value):
         """Return a string."""