Fixed #27142, #27110 -- Made makemigrations consistency checks respect database routers.

Partially reverted refs #27054 except for one of the tests as this
solution supersedes that one.

Thanks Shai Berger for the review.

2 files changed, 11 insertions, 11 deletions

diff --git a/django/core/management/commands/makemigrations.py b/django/core/management/commands/makemigrations.py
index f9f50cc2ad..2fb2d713ca 100644
--- a/django/core/management/commands/makemigrations.py
+++ b/django/core/management/commands/makemigrations.py
@@ -4,8 +4,9 @@ import warnings
 from itertools import takewhile
 
 from django.apps import apps
+from django.conf import settings
 from django.core.management.base import BaseCommand, CommandError
-from django.db import connections
+from django.db import DEFAULT_DB_ALIAS, connections, router
 from django.db.migrations import Migration
 from django.db.migrations.autodetector import MigrationAutodetector
 from django.db.migrations.loader import MigrationLoader
@@ -94,9 +95,14 @@ class Command(BaseCommand):
         loader = MigrationLoader(None, ignore_no_migrations=True)
 
         # Raise an error if any migrations are applied before their dependencies.
-        for db in connections:
-            connection = connections[db]
-            if connection.settings_dict['ENGINE'] != 'django.db.backends.dummy':
+        consistency_check_labels = set(config.label for config in apps.get_app_configs())
+        # Non-default databases are only checked if database routers used.
+        aliases_to_check = connections if settings.DATABASE_ROUTERS else [DEFAULT_DB_ALIAS]
+        for alias in sorted(aliases_to_check):
+            connection = connections[alias]
+            if (connection.settings_dict['ENGINE'] != 'django.db.backends.dummy' and
+                    # At least one app must be migrated to the database.
+                    any(router.allow_migrate(connection.alias, label) for label in consistency_check_labels)):
                 loader.check_consistent_history(connection)
 
         # Before anything else, see if there's conflicting apps and drop out
diff --git a/django/db/migrations/loader.py b/django/db/migrations/loader.py
index c78aaed573..ce6fd9e3c0 100644
--- a/django/db/migrations/loader.py
+++ b/django/db/migrations/loader.py
@@ -6,7 +6,6 @@ from importlib import import_module
 
 from django.apps import apps
 from django.conf import settings
-from django.db.migrations.exceptions import MigrationSchemaMissing
 from django.db.migrations.graph import MigrationGraph
 from django.db.migrations.recorder import MigrationRecorder
 from django.utils import six
@@ -280,12 +279,7 @@ class MigrationLoader(object):
         unapplied dependencies.
         """
         recorder = MigrationRecorder(connection)
-        try:
-            applied = recorder.applied_migrations()
-        except MigrationSchemaMissing:
-            # Skip check if the django_migrations table is missing and can't be
-            # created.
-            return
+        applied = recorder.applied_migrations()
         for migration in applied:
             # If the migration is unknown, skip it.
             if migration not in self.graph.nodes: