always use type Protocol Serializer instead of DefaultSerializer

rq/cli/cli.py

@@ -7,7 +7,7 @@
 import os
 import sys
 import warnings
-from typing import List, Type
+from typing import cast, List, Type, TYPE_CHECKING
 
 import click
 from redis.exceptions import ConnectionError
@@ -48,6 +48,9 @@
 from rq.worker_pool import WorkerPool
 from rq.worker_registration import clean_worker_registry
 
+if TYPE_CHECKING:
+    from rq.serializers import Serializer
+
 
 @click.group()
 @click.version_option(version)
@@ -461,7 +464,7 @@ def worker_pool(
     setup_loghandlers_from_args(verbose, quiet, date_format, log_format)
 
     if serializer:
-        serializer_class: Type[DefaultSerializer] = import_attribute(serializer)  # type: ignore[assignment]
+        serializer_class = cast(Type['Serializer'], import_attribute(serializer))
     else:
         serializer_class = DefaultSerializer
 

rq/worker_pool.py

@@ -60,7 +60,7 @@ def __init__(
         self._sleep: int = 0
         self.status: self.Status = self.Status.IDLE  # type: ignore
         self.worker_class: Type[BaseWorker] = worker_class
-        self.serializer: Type[DefaultSerializer] = serializer
+        self.serializer: Type['Serializer'] = serializer
         self.job_class: Type[Job] = job_class
 
         # A dictionary of WorkerData keyed by worker name
@@ -247,7 +247,7 @@ def run_worker(
     connection_pool_class,
     connection_pool_kwargs: dict,
     worker_class: Type[BaseWorker] = Worker,
-    serializer: Type[DefaultSerializer] = DefaultSerializer,
+    serializer: Type['Serializer'] = DefaultSerializer,
     job_class: Type[Job] = Job,
     burst: bool = True,
     logging_level: str = "INFO",