Fixed #31504 -- Allowed calling makemigrations without an active database connection.

django/core/management/commands/makemigrations.py

@@ -1,5 +1,6 @@
 import os
 import sys
+import warnings
 from itertools import takewhile
 
 from django.apps import apps
@@ -7,7 +8,7 @@ from django.conf import settings
 from django.core.management.base import (
     BaseCommand, CommandError, no_translations,
 )
-from django.db import DEFAULT_DB_ALIAS, connections, router
+from django.db import DEFAULT_DB_ALIAS, OperationalError, connections, router
 from django.db.migrations import Migration
 from django.db.migrations.autodetector import MigrationAutodetector
 from django.db.migrations.loader import MigrationLoader
@@ -98,8 +99,15 @@ class Command(BaseCommand):
                     for app_label in consistency_check_labels
                     for model in apps.get_app_config(app_label).get_models()
             )):
-                loader.check_consistent_history(connection)
-
+                try:
+                    loader.check_consistent_history(connection)
+                except OperationalError as error:
+                    warnings.warn(
+                        "Got an error checking a consistent migration history "
+                        "performed for database connection '%s': %s."
+                        % (alias, error),
+                        RuntimeWarning,
+                    )
         # Before anything else, see if there's conflicting apps and drop out
         # hard if there are any and they don't want to merge
         conflicts = loader.detect_conflicts()

docs/ref/django-admin.txt

@@ -824,6 +824,12 @@ Generate migration files without Django version and timestamp header.
 Makes ``makemigrations`` exit with a non-zero status when model changes without
 migrations are detected.
 
+.. versionchanged:: 3.2
+
+    Support for calling ``makemigrations`` without an active database
+    connection was added. In that case, check for a consistent migration
+    history is skipped.
+
 ``migrate``
 -----------
 

docs/releases/3.2.txt

@@ -157,6 +157,10 @@ Management Commands
 * :djadmin:`loaddata` now supports fixtures stored in XZ archives (``.xz``) and
   LZMA archives (``.lzma``).
 
+* :djadmin:`makemigrations` can now be called without an active database
+  connection. In that case, check for a consistent migration history is
+  skipped.
+
 Migrations
 ~~~~~~~~~~
 

tests/migrations/test_commands.py

@@ -8,7 +8,8 @@ from unittest import mock
 from django.apps import apps
 from django.core.management import CommandError, call_command
 from django.db import (
-    ConnectionHandler, DatabaseError, connection, connections, models,
+    ConnectionHandler, DatabaseError, OperationalError, connection,
+    connections, models,
 )
 from django.db.backends.base.schema import BaseDatabaseSchemaEditor
 from django.db.backends.utils import truncate_name
@@ -1555,6 +1556,19 @@ class MakeMigrationsTests(MigrationTestBase):
             with self.assertRaisesMessage(InconsistentMigrationHistory, msg):
                 call_command("makemigrations")
 
+    def test_makemigrations_inconsistent_history_db_failure(self):
+        msg = (
+            "Got an error checking a consistent migration history performed "
+            "for database connection 'default': could not connect to server"
+        )
+        with mock.patch(
+            'django.db.migrations.loader.MigrationLoader.check_consistent_history',
+            side_effect=OperationalError('could not connect to server'),
+        ):
+            with self.temporary_migration_module():
+                with self.assertWarnsMessage(RuntimeWarning, msg):
+                    call_command('makemigrations', verbosity=0)
+
     @mock.patch('builtins.input', return_value='1')
     @mock.patch('django.db.migrations.questioner.sys.stdin', mock.MagicMock(encoding=sys.getdefaultencoding()))
     def test_makemigrations_auto_now_add_interactive(self, *args):