Serialize arguments in task, rather than each backend

This avoids duplication, and makes backend implementations simpler

django/tasks/backends/dummy.py

@@ -5,7 +5,7 @@ from django.db import transaction
 from django.tasks.exceptions import ResultDoesNotExist
 from django.tasks.signals import task_enqueued
 from django.tasks.task import ResultStatus, TaskResult
-from django.tasks.utils import get_random_id, json_normalize
+from django.tasks.utils import get_random_id
 from django.utils import timezone
 
 from .base import BaseTaskBackend
@@ -35,8 +35,8 @@ class DummyBackend(BaseTaskBackend):
             enqueued_at=None,
             started_at=None,
             finished_at=None,
-            args=json_normalize(args),
-            kwargs=json_normalize(kwargs),
+            args=args,
+            kwargs=kwargs,
             backend=self.alias,
         )
 

django/tasks/backends/immediate.py

@@ -70,8 +70,8 @@ class ImmediateBackend(BaseTaskBackend):
             enqueued_at=None,
             started_at=None,
             finished_at=None,
-            args=json_normalize(args),
-            kwargs=json_normalize(kwargs),
+            args=args,
+            kwargs=kwargs,
             backend=self.alias,
         )
 

django/tasks/task.py

@@ -10,7 +10,7 @@ from django.utils import timezone
 from django.utils.translation import gettext_lazy as _
 
 from .exceptions import ResultDoesNotExist
-from .utils import exception_from_dict, get_module_path
+from .utils import exception_from_dict, get_module_path, json_normalize
 
 DEFAULT_TASK_BACKEND_ALIAS = "default"
 DEFAULT_QUEUE_NAME = "default"
@@ -100,13 +100,17 @@ class Task:
         """
         Queue up the task to be executed
         """
-        return self.get_backend().enqueue(self, args, kwargs)
+        return self.get_backend().enqueue(
+            self, json_normalize(args), json_normalize(kwargs)
+        )
 
     async def aenqueue(self, *args, **kwargs):
         """
         Queue up a task function (or coroutine) to be executed
         """
-        return await self.get_backend().aenqueue(self, args, kwargs)
+        return await self.get_backend().aenqueue(
+            self, json_normalize(args), json_normalize(kwargs)
+        )
 
     def get_result(self, result_id):
         """

tests/tasks/test_tasks.py

@@ -68,6 +68,18 @@ class TaskTestCase(SimpleTestCase):
 
         self.assertEqual(default_task_backend.results, [result])
 
+    def test_enqueue_with_invalid_argument(self):
+        with self.assertRaisesMessage(
+            TypeError, "Object of type datetime is not JSON serializable"
+        ):
+            test_tasks.noop_task.enqueue(datetime.now())
+
+    async def test_aenqueue_with_invalid_argument(self):
+        with self.assertRaisesMessage(
+            TypeError, "Object of type datetime is not JSON serializable"
+        ):
+            await test_tasks.noop_task.aenqueue(datetime.now())
+
     def test_using_priority(self):
         self.assertEqual(test_tasks.noop_task.priority, 0)
         self.assertEqual(test_tasks.noop_task.using(priority=1).priority, 1)