Add RequestFingerprinterProtocol.

scrapy/dupefilters.py

@@ -12,7 +12,11 @@ from scrapy.settings import BaseSettings
 from scrapy.spiders import Spider
 from scrapy.utils.deprecate import ScrapyDeprecationWarning
 from scrapy.utils.job import job_dir
-from scrapy.utils.request import RequestFingerprinter, referer_str
+from scrapy.utils.request import (
+    RequestFingerprinter,
+    RequestFingerprinterProtocol,
+    referer_str,
+)
 
 if TYPE_CHECKING:
     # typing.Self requires Python 3.11
@@ -48,10 +52,10 @@ class RFPDupeFilter(BaseDupeFilter):
         path: Optional[str] = None,
         debug: bool = False,
         *,
-        fingerprinter: Optional[RequestFingerprinter] = None,
+        fingerprinter: Optional[RequestFingerprinterProtocol] = None,
     ) -> None:
         self.file = None
-        self.fingerprinter: RequestFingerprinter = (
+        self.fingerprinter: RequestFingerprinterProtocol = (
             fingerprinter or RequestFingerprinter()
         )
         self.fingerprints: Set[str] = set()
@@ -68,7 +72,7 @@ class RFPDupeFilter(BaseDupeFilter):
         cls,
         settings: BaseSettings,
         *,
-        fingerprinter: Optional[RequestFingerprinter] = None,
+        fingerprinter: Optional[RequestFingerprinterProtocol] = None,
     ) -> Self:
         debug = settings.getbool("DUPEFILTER_DEBUG")
         try:

scrapy/utils/request.py

@@ -14,6 +14,7 @@ from typing import (
     Iterable,
     List,
     Optional,
+    Protocol,
     Tuple,
     Type,
     Union,
@@ -230,6 +231,11 @@ def fingerprint(
     return cache[cache_key]
 
 
+class RequestFingerprinterProtocol(Protocol):
+    def fingerprint(self, request: Request) -> bytes:
+        ...
+
+
 class RequestFingerprinter:
     """Default fingerprinter.