From 9756c334294ad573d887b449e2fe1cc87387af40 Mon Sep 17 00:00:00 2001
From: wtkm11 <wtkm11@users.noreply.github.com>
Date: Sat, 25 Apr 2020 14:54:20 -0400
Subject: [PATCH] Fixed #31504 -- Allowed calling makemigrations without an
 active database connection.

---
 .../core/management/commands/makemigrations.py   | 14 +++++++++++---
 docs/ref/django-admin.txt                        |  6 ++++++
 docs/releases/3.2.txt                            |  4 ++++
 tests/migrations/test_commands.py                | 16 +++++++++++++++-
 4 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/django/core/management/commands/makemigrations.py b/django/core/management/commands/makemigrations.py
index 7cee2c120e3..709abaa8d6b 100644
--- a/django/core/management/commands/makemigrations.py
+++ b/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()
diff --git a/docs/ref/django-admin.txt b/docs/ref/django-admin.txt
index 4cd477b7a85..46e048e6485 100644
--- a/docs/ref/django-admin.txt
+++ b/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``
 -----------
 
diff --git a/docs/releases/3.2.txt b/docs/releases/3.2.txt
index b1a0e19edb2..1603f8f1b30 100644
--- a/docs/releases/3.2.txt
+++ b/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
 ~~~~~~~~~~
 
diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index a0b33ca6f5f..69fdf287476 100644
--- a/tests/migrations/test_commands.py
+++ b/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):