carltongibson / issue31262

Reproduce for performance regression on PR 12449 django/django#12449

• Create a new venv
• pip install -e path/to/django
• pip install django-debug-toolbar
• ./manage.py migrate
• ./manage.py loaddata fixtures.json
• ./manage.py createsuperuser
• ./manage.py runserver

Visit: http://127.0.0.1:8000/admin/example/book/

• 14 queries on master/3.1.x
• 74 queries on pull/12449/head

14 and 74 is too high:

• there's an issue with debug-toolbar-duplicating queries
• jazzband/django-debug-toolbar#1239
• Comment out overriding chunked_cursor in site-packages/debug_toolbar/panels/sql/tracking.py to see it properly.
• It's about 11 vs 45, like so, but still.

This diff fixes the regression:

(django) django (pr/12449)$ git diff django/forms/fields.py
diff --git a/django/forms/fields.py b/django/forms/fields.py
index 0728db9922..32153819ff 100644
--- a/django/forms/fields.py
+++ b/django/forms/fields.py
@@ -791,7 +791,7 @@ class ChoiceField(Field):

         # Setting choices on the field also sets the choices on the widget.
         # Note that we bypass the property setter to avoid re-normalizing.
-        self._choices = self.widget._choices = value
+        self._choices = self.widget.choices = value

     def to_python(self, value):
         """Return a string."""