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.

14 files changed, 87 insertions, 2 deletions

diff --git a/django/apps/config.py b/django/apps/config.py
index 928e19ac44..6d794eee3a 100644
--- a/django/apps/config.py
+++ b/django/apps/config.py
@@ -5,6 +5,7 @@ from importlib import import_module
 
 from django.core.exceptions import ImproperlyConfigured
 from django.utils.deprecation import RemovedInDjango41Warning
+from django.utils.functional import cached_property
 from django.utils.module_loading import import_string, module_has_submodule
 
 APPS_MODULE_NAME = 'apps'
@@ -55,6 +56,15 @@ class AppConfig:
     def __repr__(self):
         return '<%s: %s>' % (self.__class__.__name__, self.label)
 
+    @cached_property
+    def default_auto_field(self):
+        from django.conf import settings
+        return settings.DEFAULT_AUTO_FIELD
+
+    @property
+    def _is_default_auto_field_overridden(self):
+        return self.__class__.default_auto_field is not AppConfig.default_auto_field
+
     def _path_from_module(self, module):
         """Attempt to determine app's filesystem path from its module."""
         # See #21874 for extended discussion of the behavior of this method in
diff --git a/django/conf/app_template/apps.py-tpl b/django/conf/app_template/apps.py-tpl
index 9b2ce5289c..b705352181 100644
--- a/django/conf/app_template/apps.py-tpl
+++ b/django/conf/app_template/apps.py-tpl
@@ -2,4 +2,5 @@ from django.apps import AppConfig
 
 
 class {{ camel_case_app_name }}Config(AppConfig):
+    default_auto_field = 'django.db.models.BigAutoField'
     name = '{{ app_name }}'
diff --git a/django/conf/global_settings.py b/django/conf/global_settings.py
index 381ad63ae6..cf9fae496e 100644
--- a/django/conf/global_settings.py
+++ b/django/conf/global_settings.py
@@ -414,6 +414,9 @@ THOUSAND_SEPARATOR = ','
 DEFAULT_TABLESPACE = ''
 DEFAULT_INDEX_TABLESPACE = ''
 
+# Default primary key field type.
+DEFAULT_AUTO_FIELD = 'django.db.models.AutoField'
+
 # Default X-Frame-Options header value
 X_FRAME_OPTIONS = 'DENY'
 
diff --git a/django/conf/project_template/project_name/settings.py-tpl b/django/conf/project_template/project_name/settings.py-tpl
index 444c899b2b..7830fb2f3c 100644
--- a/django/conf/project_template/project_name/settings.py-tpl
+++ b/django/conf/project_template/project_name/settings.py-tpl
@@ -118,3 +118,8 @@ USE_TZ = True
 # https://docs.djangoproject.com/en/{{ docs_version }}/howto/static-files/
 
 STATIC_URL = '/static/'
+
+# Default primary key field type
+# https://docs.djangoproject.com/en/{{ docs_version }}/ref/settings/#default-auto-field
+
+DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'
diff --git a/django/contrib/admin/apps.py b/django/contrib/admin/apps.py
index 85e9ff830a..c4fba8837c 100644
--- a/django/contrib/admin/apps.py
+++ b/django/contrib/admin/apps.py
@@ -7,6 +7,7 @@ from django.utils.translation import gettext_lazy as _
 class SimpleAdminConfig(AppConfig):
     """Simple AppConfig which does not do automatic discovery."""
 
+    default_auto_field = 'django.db.models.AutoField'
     default_site = 'django.contrib.admin.sites.AdminSite'
     name = 'django.contrib.admin'
     verbose_name = _("Administration")
diff --git a/django/contrib/auth/apps.py b/django/contrib/auth/apps.py
index b9d271bb1f..4e4ef06d27 100644
--- a/django/contrib/auth/apps.py
+++ b/django/contrib/auth/apps.py
@@ -11,6 +11,7 @@ from .signals import user_logged_in
 
 
 class AuthConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'django.contrib.auth'
     verbose_name = _("Authentication and Authorization")
 
diff --git a/django/contrib/contenttypes/apps.py b/django/contrib/contenttypes/apps.py
index 1a8e25b98e..390afb3fcf 100644
--- a/django/contrib/contenttypes/apps.py
+++ b/django/contrib/contenttypes/apps.py
@@ -12,6 +12,7 @@ from .management import (
 
 
 class ContentTypesConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'django.contrib.contenttypes'
     verbose_name = _("Content Types")
 
diff --git a/django/contrib/flatpages/apps.py b/django/contrib/flatpages/apps.py
index 330ee05063..4f5ef17004 100644
--- a/django/contrib/flatpages/apps.py
+++ b/django/contrib/flatpages/apps.py
@@ -3,5 +3,6 @@ from django.utils.translation import gettext_lazy as _
 
 
 class FlatPagesConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'django.contrib.flatpages'
     verbose_name = _("Flat Pages")
diff --git a/django/contrib/gis/apps.py b/django/contrib/gis/apps.py
index 662ae43d8d..e582e76760 100644
--- a/django/contrib/gis/apps.py
+++ b/django/contrib/gis/apps.py
@@ -4,6 +4,7 @@ from django.utils.translation import gettext_lazy as _
 
 
 class GISConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'django.contrib.gis'
     verbose_name = _("GIS")
 
diff --git a/django/contrib/redirects/apps.py b/django/contrib/redirects/apps.py
index cab67424e7..c1d80ee3c1 100644
--- a/django/contrib/redirects/apps.py
+++ b/django/contrib/redirects/apps.py
@@ -3,5 +3,6 @@ from django.utils.translation import gettext_lazy as _
 
 
 class RedirectsConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'django.contrib.redirects'
     verbose_name = _("Redirects")
diff --git a/django/contrib/sitemaps/apps.py b/django/contrib/sitemaps/apps.py
index 502d6890d0..ec795eab87 100644
--- a/django/contrib/sitemaps/apps.py
+++ b/django/contrib/sitemaps/apps.py
@@ -3,5 +3,6 @@ from django.utils.translation import gettext_lazy as _
 
 
 class SiteMapsConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'django.contrib.sitemaps'
     verbose_name = _("Site Maps")
diff --git a/django/contrib/sites/apps.py b/django/contrib/sites/apps.py
index ed52d34786..7f820dcc79 100644
--- a/django/contrib/sites/apps.py
+++ b/django/contrib/sites/apps.py
@@ -8,6 +8,7 @@ from .management import create_default_site
 
 
 class SitesConfig(AppConfig):
+    default_auto_field = 'django.db.models.AutoField'
     name = 'django.contrib.sites'
     verbose_name = _("Sites")
 
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 = []
diff --git a/django/db/models/options.py b/django/db/models/options.py
index 0e28b6812a..4028e05b99 100644
--- a/django/db/models/options.py
+++ b/django/db/models/options.py
@@ -5,12 +5,13 @@ from collections import defaultdict
 
 from django.apps import apps
 from django.conf import settings
-from django.core.exceptions import FieldDoesNotExist
+from django.core.exceptions import FieldDoesNotExist, ImproperlyConfigured
 from django.db import connections
 from django.db.models import AutoField, Manager, OrderWrt, UniqueConstraint
 from django.db.models.query_utils import PathInfo
 from django.utils.datastructures import ImmutableList, OrderedSet
 from django.utils.functional import cached_property
+from django.utils.module_loading import import_string
 from django.utils.text import camel_case_to_spaces, format_lazy
 from django.utils.translation import override
 
@@ -217,6 +218,37 @@ class Options:
             new_objs.append(obj)
         return new_objs
 
+    def _get_default_pk_class(self):
+        pk_class_path = getattr(
+            self.app_config,
+            'default_auto_field',
+            settings.DEFAULT_AUTO_FIELD,
+        )
+        if self.app_config and self.app_config._is_default_auto_field_overridden:
+            app_config_class = type(self.app_config)
+            source = (
+                f'{app_config_class.__module__}.'
+                f'{app_config_class.__qualname__}.default_auto_field'
+            )
+        else:
+            source = 'DEFAULT_AUTO_FIELD'
+        if not pk_class_path:
+            raise ImproperlyConfigured(f'{source} must not be empty.')
+        try:
+            pk_class = import_string(pk_class_path)
+        except ImportError as e:
+            msg = (
+                f"{source} refers to the module '{pk_class_path}' that could "
+                f"not be imported."
+            )
+            raise ImproperlyConfigured(msg) from e
+        if not issubclass(pk_class, AutoField):
+            raise ValueError(
+                f"Primary key '{pk_class_path}' referred by {source} must "
+                f"subclass AutoField."
+            )
+        return pk_class
+
     def _prepare(self, model):
         if self.order_with_respect_to:
             # The app registry will not be ready at this point, so we cannot
@@ -250,7 +282,8 @@ class Options:
                 field.primary_key = True
                 self.setup_pk(field)
             else:
-                auto = AutoField(verbose_name='ID', primary_key=True, auto_created=True)
+                pk_class = self._get_default_pk_class()
+                auto = pk_class(verbose_name='ID', primary_key=True, auto_created=True)
                 model.add_to_class('id', auto)
 
     def add_manager(self, manager):