Refs #31055 -- Added --database option to the check management command.

This avoids enabling the ``database`` checks unless they are explicitly
requested and allows to disable on a per-alias basis which is required
when only creating a subset of the test databases.

This also removes unnecessary BaseCommand._run_checks() hook.

tests/check_framework/test_database.py

@@ -1,8 +1,7 @@
 import unittest
 from unittest import mock
 
-from django.core.checks import Tags, run_checks
-from django.core.checks.registry import CheckRegistry
+from django.core.checks.database import check_database_backends
 from django.db import connection
 from django.test import TestCase
 
@@ -10,30 +9,12 @@ from django.test import TestCase
 class DatabaseCheckTests(TestCase):
     databases = {'default', 'other'}
 
-    @property
-    def func(self):
-        from django.core.checks.database import check_database_backends
-        return check_database_backends
-
-    def test_database_checks_not_run_by_default(self):
-        """
-        `database` checks are only run when their tag is specified.
-        """
-        def f1(**kwargs):
-            return [5]
-
-        registry = CheckRegistry()
-        registry.register(Tags.database)(f1)
-        errors = registry.run_checks()
-        self.assertEqual(errors, [])
-
-        errors2 = registry.run_checks(tags=[Tags.database])
-        self.assertEqual(errors2, [5])
-
-    def test_database_checks_called(self):
-        with mock.patch('django.db.backends.base.validation.BaseDatabaseValidation.check') as mocked_check:
-            run_checks(tags=[Tags.database])
-            self.assertTrue(mocked_check.called)
+    @mock.patch('django.db.backends.base.validation.BaseDatabaseValidation.check')
+    def test_database_checks_called(self, mocked_check):
+        check_database_backends()
+        self.assertFalse(mocked_check.called)
+        check_database_backends(databases=self.databases)
+        self.assertTrue(mocked_check.called)
 
     @unittest.skipUnless(connection.vendor == 'mysql', 'Test only for MySQL')
     def test_mysql_strict_mode(self):
@@ -47,7 +28,7 @@ class DatabaseCheckTests(TestCase):
                 'django.db.backends.utils.CursorWrapper.fetchone', create=True,
                 return_value=(response,)
             ):
-                self.assertEqual(self.func(None), [])
+                self.assertEqual(check_database_backends(databases=self.databases), [])
 
         bad_sql_modes = ['', 'WHATEVER']
         for response in bad_sql_modes:
@@ -56,6 +37,6 @@ class DatabaseCheckTests(TestCase):
                 return_value=(response,)
             ):
                 # One warning for each database alias
-                result = self.func(None)
+                result = check_database_backends(databases=self.databases)
                 self.assertEqual(len(result), 2)
                 self.assertEqual([r.id for r in result], ['mysql.W002', 'mysql.W002'])