Fixed #31007 -- Allowed specifying type of auto-created primary keys.

This also changes the default type of auto-created primary keys
for new apps and projects to BigAutoField.

1 files changed, 25 insertions, 0 deletions

diff --git a/django/db/models/base.py b/django/db/models/base.py
index de044886c3..822aad080d 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -1290,11 +1290,36 @@ class Model(metaclass=ModelBase):
                 *cls._check_indexes(databases),
                 *cls._check_ordering(),
                 *cls._check_constraints(databases),
+                *cls._check_default_pk(),
             ]
 
         return errors
 
     @classmethod
+    def _check_default_pk(cls):
+        if (
+            cls._meta.pk.auto_created and
+            not settings.is_overridden('DEFAULT_AUTO_FIELD') and
+            not cls._meta.app_config._is_default_auto_field_overridden
+        ):
+            return [
+                checks.Warning(
+                    f"Auto-created primary key used when not defining a "
+                    f"primary key type, by default "
+                    f"'{settings.DEFAULT_AUTO_FIELD}'.",
+                    hint=(
+                        f"Configure the DEFAULT_AUTO_FIELD setting or the "
+                        f"{cls._meta.app_config.__class__.__qualname__}."
+                        f"default_auto_field attribute to point to a subclass "
+                        f"of AutoField, e.g. 'django.db.models.BigAutoField'."
+                    ),
+                    obj=cls,
+                    id='models.W042',
+                ),
+            ]
+        return []
+
+    @classmethod
     def _check_swappable(cls):
         """Check if the swapped model exists."""
         errors = []