Ensure the given backend is a database backend

Author: RealOrangeOne

django_tasks/backends/database/management/commands/db_worker.py

@@ -10,6 +10,7 @@
 from django.db import transaction
 
 from django_tasks import DEFAULT_TASK_BACKEND_ALIAS, tasks
+from django_tasks.backends.database.backend import DatabaseBackend
 from django_tasks.backends.database.models import DBTaskResult
 from django_tasks.exceptions import InvalidTaskBackendError
 from django_tasks.task import DEFAULT_QUEUE_NAME, ResultStatus
@@ -129,9 +130,11 @@ def run_task(self, db_task_result: DBTaskResult) -> None:
 
 def valid_backend_name(val: str) -> str:
     try:
-        tasks[val]
+        backend = tasks[val]
     except InvalidTaskBackendError as e:
         raise ArgumentTypeError(e.args[0]) from e
+    if not isinstance(backend, DatabaseBackend):
+        raise ArgumentTypeError(f"Backend '{val}' is not a database backend")
     return val
 
 

tests/tests/test_database_backend.py

@@ -311,6 +311,15 @@ def test_unknown_backend(self) -> None:
                 )
         self.assertIn("The connection 'unknown' doesn't exist.", output.getvalue())
 
+    def test_incorrect_backend(self) -> None:
+        output = StringIO()
+        with redirect_stderr(output):
+            with self.assertRaises(SystemExit):
+                execute_from_command_line(
+                    ["django-admin", "db_worker", "--backend", "dummy"]
+                )
+        self.assertIn("Backend 'dummy' is not a database backend", output.getvalue())
+
     def test_negative_interval(self) -> None:
         output = StringIO()
         with redirect_stderr(output):