added warning for incompatibility with middleware_classes setting. (#1217)

* added warning for incompatibility with middleware_classes setting.
* added test for middleware_classes error check

Author: Mohammad Rabetian

debug_toolbar/apps.py

@@ -21,6 +21,17 @@ def check_middleware(app_configs, **kwargs):
     gzip_index = None
     debug_toolbar_indexes = []
 
+    # If old style MIDDLEWARE_CLASSES is being used, report an error.
+    if settings.is_overridden("MIDDLEWARE_CLASSES"):
+        errors.append(
+            Warning(
+                "debug_toolbar is incompatible with MIDDLEWARE_CLASSES setting.",
+                hint="Use MIDDLEWARE instead of MIDDLEWARE_CLASSES",
+                id="debug_toolbar.W004",
+            )
+        )
+        return errors
+
     # Determine the indexes which gzip and/or the toolbar are installed at
     for i, middleware in enumerate(settings.MIDDLEWARE):
         if is_middleware_class(GZipMiddleware, middleware):

tests/test_integration.py

@@ -411,3 +411,23 @@ def test_check_gzip_middleware_error(self):
                 )
             ],
         )
+
+    @override_settings(
+        MIDDLEWARE_CLASSES=[
+            "django.contrib.messages.middleware.MessageMiddleware",
+            "django.contrib.sessions.middleware.SessionMiddleware",
+            "django.contrib.auth.middleware.AuthenticationMiddleware",
+            "django.middleware.gzip.GZipMiddleware",
+            "debug_toolbar.middleware.DebugToolbarMiddleware",
+        ]
+    )
+    def test_check_middleware_classes_error(self):
+        messages = run_checks()
+        self.assertIn(
+            Warning(
+                "debug_toolbar is incompatible with MIDDLEWARE_CLASSES setting.",
+                hint="Use MIDDLEWARE instead of MIDDLEWARE_CLASSES",
+                id="debug_toolbar.W004",
+            ),
+            messages,
+        )