Link tasks to their restarts

Closes #1711 (closed)

arkindex/ponos/api.py

@@ -223,12 +223,9 @@ class TaskRestart(ProcessACLMixin, CreateAPIView):
             raise ValidationError(
                 detail="Task's state must be in a final state to be restarted."
             )
-        # TODO Check the original_task_id field directly once it is implemented
-        # https://gitlab.teklia.com/arkindex/frontend/-/issues/1383
-        _, *suffix = task.slug.rsplit("_old", 1)
-        if suffix:
+        if task.restarts.exists():
             raise ValidationError(
-                detail="This task has already been restarted"
+                detail="This task has already been restarted."
             )
         return task
 
@@ -238,7 +235,10 @@ class TaskRestart(ProcessACLMixin, CreateAPIView):
         parents = list(copy.parents.all())
 
         # Rename the original task
-        basename, *_ = copy.slug.rsplit("_old", 1)
+        if copy.original_task_id:
+            basename, *_ = copy.slug.rsplit("_old", 1)
+        else:
+            basename = copy.slug
         latest_task = Task.objects.filter(run=copy.run, slug__startswith=f"{basename}_old").order_by("-created").first()
         if not latest_task:
             # There is no previously restarted task: the original task will have the slug slug_old1
@@ -251,6 +251,7 @@ class TaskRestart(ProcessACLMixin, CreateAPIView):
         copy.save()
 
         # Copy the original task
+        copy.original_task_id = copy.id
         copy.id = uuid.uuid4()
         copy.slug = basename
         copy.state = State.Pending