Add missing type hints for retry.py (#3250)

Add missing type hints in the retry.py file and related tests.

redis/retry.py

@@ -1,17 +1,27 @@
 import socket
 from time import sleep
+from typing import TYPE_CHECKING, Any, Callable, Iterable, Tuple, Type, TypeVar
 
 from redis.exceptions import ConnectionError, TimeoutError
 
+T = TypeVar("T")
+
+if TYPE_CHECKING:
+    from redis.backoff import AbstractBackoff
+
 
 class Retry:
     """Retry a specific number of times after a failure"""
 
     def __init__(
         self,
-        backoff,
-        retries,
-        supported_errors=(ConnectionError, TimeoutError, socket.timeout),
+        backoff: "AbstractBackoff",
+        retries: int,
+        supported_errors: Tuple[Type[Exception], ...] = (
+            ConnectionError,
+            TimeoutError,
+            socket.timeout,
+        ),
     ):
         """
         Initialize a `Retry` object with a `Backoff` object
@@ -24,15 +34,21 @@ def __init__(
         self._retries = retries
         self._supported_errors = supported_errors
 
-    def update_supported_errors(self, specified_errors: list):
+    def update_supported_errors(
+        self, specified_errors: Iterable[Type[Exception]]
+    ) -> None:
         """
         Updates the supported errors with the specified error types
         """
         self._supported_errors = tuple(
             set(self._supported_errors + tuple(specified_errors))
         )
 
-    def call_with_retry(self, do, fail):
+    def call_with_retry(
+        self,
+        do: Callable[[], T],
+        fail: Callable[[Exception], Any],
+    ) -> T:
         """
         Execute an operation that might fail and returns its result, or
         raise the exception that was thrown depending on the `Backoff` object.

tests/test_retry.py

@@ -1,7 +1,7 @@
 from unittest.mock import patch
 
 import pytest
-from redis.backoff import ExponentialBackoff, NoBackoff
+from redis.backoff import AbstractBackoff, ExponentialBackoff, NoBackoff
 from redis.client import Redis
 from redis.connection import Connection, UnixDomainSocketConnection
 from redis.exceptions import (
@@ -15,7 +15,7 @@
 from .conftest import _get_client
 
 
-class BackoffMock:
+class BackoffMock(AbstractBackoff):
     def __init__(self):
         self.reset_calls = 0
         self.calls = 0