Fixed #35920 -- Observed requires_system_checks in migrate and runserver.

Before, the full suite of system checks was run by these commands
regardless if requires_system_checks had been overridden.

Co-authored-by: Simon Charette <charette.s@gmail.com>

tests/admin_scripts/tests.py

@@ -20,6 +20,8 @@ from user_commands.utils import AssertFormatterFailureCaughtContext
 
 from django import conf, get_version
 from django.conf import settings
+from django.core.checks import Error, Tags, register
+from django.core.checks.registry import registry
 from django.core.management import (
     BaseCommand,
     CommandError,
@@ -27,7 +29,7 @@ from django.core.management import (
     color,
     execute_from_command_line,
 )
-from django.core.management.base import LabelCommand
+from django.core.management.base import LabelCommand, SystemCheckError
 from django.core.management.commands.loaddata import Command as LoaddataCommand
 from django.core.management.commands.runserver import Command as RunserverCommand
 from django.core.management.commands.testserver import Command as TestserverCommand
@@ -1733,7 +1735,53 @@ class ManageRunserver(SimpleTestCase):
             stdout=self.output,
         )
         self.assertIn("Performing system checks...", self.output.getvalue())
-        mocked_check.assert_called()
+        mocked_check.assert_has_calls(
+            [mock.call(tags=set()), mock.call(display_num_errors=True)]
+        )
+
+    def test_custom_system_checks(self):
+        original_checks = registry.registered_checks.copy()
+
+        @register(Tags.signals)
+        def my_check(app_configs, **kwargs):
+            return [Error("my error")]
+
+        class CustomException(Exception):
+            pass
+
+        self.addCleanup(setattr, registry, "registered_checks", original_checks)
+
+        class CustomRunserverCommand(RunserverCommand):
+            """Rather than mock run(), raise immediately after system checks run."""
+
+            def check_migrations(self, *args, **kwargs):
+                raise CustomException
+
+        class CustomRunserverCommandWithSignalsChecks(CustomRunserverCommand):
+            requires_system_checks = [Tags.signals]
+
+        command = CustomRunserverCommandWithSignalsChecks()
+        with self.assertRaises(SystemCheckError):
+            call_command(
+                command,
+                use_reloader=False,
+                skip_checks=False,
+                stdout=StringIO(),
+                stderr=StringIO(),
+            )
+
+        class CustomMigrateCommandWithSecurityChecks(CustomRunserverCommand):
+            requires_system_checks = [Tags.security]
+
+        command = CustomMigrateCommandWithSecurityChecks()
+        with self.assertRaises(CustomException):
+            call_command(
+                command,
+                use_reloader=False,
+                skip_checks=False,
+                stdout=StringIO(),
+                stderr=StringIO(),
+            )
 
 
 class ManageRunserverMigrationWarning(TestCase):