From 89503ae3f1228e9406428a19bc6c49c1f8e9e19b Mon Sep 17 00:00:00 2001
From: Andrey Rakhmatullin <wrar@wrar.name>
Date: Mon, 7 Aug 2023 00:41:11 +0400
Subject: [PATCH] Full typing for scrapy/dupefilters.py.

---
 scrapy/dupefilters.py | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/scrapy/dupefilters.py b/scrapy/dupefilters.py
index d796e5cbb..bc912268c 100644
--- a/scrapy/dupefilters.py
+++ b/scrapy/dupefilters.py
@@ -1,6 +1,8 @@
+from __future__ import annotations
+
 import logging
 from pathlib import Path
-from typing import Optional, Set, Type, TypeVar
+from typing import TYPE_CHECKING, Optional, Set
 from warnings import warn
 
 from twisted.internet.defer import Deferred
@@ -12,14 +14,16 @@ from scrapy.utils.deprecate import ScrapyDeprecationWarning
 from scrapy.utils.job import job_dir
 from scrapy.utils.request import RequestFingerprinter, referer_str
 
-BaseDupeFilterTV = TypeVar("BaseDupeFilterTV", bound="BaseDupeFilter")
+if TYPE_CHECKING:
+    # typing.Self requires Python 3.11
+    from typing_extensions import Self
+
+    from scrapy.crawler import Crawler
 
 
 class BaseDupeFilter:
     @classmethod
-    def from_settings(
-        cls: Type[BaseDupeFilterTV], settings: BaseSettings
-    ) -> BaseDupeFilterTV:
+    def from_settings(cls, settings: BaseSettings) -> Self:
         return cls()
 
     def request_seen(self, request: Request) -> bool:
@@ -36,9 +40,6 @@ class BaseDupeFilter:
         pass
 
 
-RFPDupeFilterTV = TypeVar("RFPDupeFilterTV", bound="RFPDupeFilter")
-
-
 class RFPDupeFilter(BaseDupeFilter):
     """Request Fingerprint duplicates filter"""
 
@@ -47,10 +48,12 @@ class RFPDupeFilter(BaseDupeFilter):
         path: Optional[str] = None,
         debug: bool = False,
         *,
-        fingerprinter=None,
+        fingerprinter: Optional[RequestFingerprinter] = None,
     ) -> None:
         self.file = None
-        self.fingerprinter = fingerprinter or RequestFingerprinter()
+        self.fingerprinter: RequestFingerprinter = (
+            fingerprinter or RequestFingerprinter()
+        )
         self.fingerprints: Set[str] = set()
         self.logdupes = True
         self.debug = debug
@@ -62,8 +65,11 @@ class RFPDupeFilter(BaseDupeFilter):
 
     @classmethod
     def from_settings(
-        cls: Type[RFPDupeFilterTV], settings: BaseSettings, *, fingerprinter=None
-    ) -> RFPDupeFilterTV:
+        cls,
+        settings: BaseSettings,
+        *,
+        fingerprinter: Optional[RequestFingerprinter] = None,
+    ) -> Self:
         debug = settings.getbool("DUPEFILTER_DEBUG")
         try:
             return cls(job_dir(settings), debug, fingerprinter=fingerprinter)
@@ -75,11 +81,11 @@ class RFPDupeFilter(BaseDupeFilter):
                 ScrapyDeprecationWarning,
             )
             result = cls(job_dir(settings), debug)
-            result.fingerprinter = fingerprinter
+            result.fingerprinter = fingerprinter or RequestFingerprinter()
             return result
 
     @classmethod
-    def from_crawler(cls, crawler):
+    def from_crawler(cls, crawler: Crawler) -> Self:
         try:
             return cls.from_settings(
                 crawler.settings,