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docs/topics/request-response.rst

@@ -469,36 +469,6 @@ import path.
 
 .. autoclass:: scrapy.utils.request.RequestFingerprinter
 
-
-.. setting:: REQUEST_FINGERPRINTER_IMPLEMENTATION
-
-REQUEST_FINGERPRINTER_IMPLEMENTATION
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-.. versionadded:: 2.7
-
-Default: ``'2.7'``
-
-Determines which request fingerprinting algorithm is used by the default
-request fingerprinter class (see :setting:`REQUEST_FINGERPRINTER_CLASS`).
-
-Possible value is:
-
--   ``'2.7'``
-
-    This implementation was introduced in Scrapy 2.7 to fix an issue of the
-    previous implementation.
-
-    New projects should use this value. The :command:`startproject` command
-    sets this value in the generated ``settings.py`` file.
-
-Scenarios where changing the request fingerprinting algorithm may cause
-undesired results include, for example, using the HTTP cache middleware (see
-:class:`~scrapy.downloadermiddlewares.httpcache.HttpCacheMiddleware`).
-Changing the request fingerprinting algorithm would invalidate the current
-cache, requiring you to redownload all requests again.
-
-
 .. _custom-request-fingerprinter:
 
 Writing your own request fingerprinter

scrapy/settings/default_settings.py

@@ -260,7 +260,7 @@ REFERER_ENABLED = True
 REFERRER_POLICY = "scrapy.spidermiddlewares.referer.DefaultReferrerPolicy"
 
 REQUEST_FINGERPRINTER_CLASS = "scrapy.utils.request.RequestFingerprinter"
-REQUEST_FINGERPRINTER_IMPLEMENTATION = "2.7"
+REQUEST_FINGERPRINTER_IMPLEMENTATION = "SENTINEL"
 
 RETRY_ENABLED = True
 RETRY_TIMES = 2  # initial response + 2 retries = 3 requests

scrapy/templates/project/module/settings.py.tmpl

@@ -88,6 +88,5 @@ ROBOTSTXT_OBEY = True
 #HTTPCACHE_STORAGE = "scrapy.extensions.httpcache.FilesystemCacheStorage"
 
 # Set settings whose default value is deprecated to a future-proof value
-REQUEST_FINGERPRINTER_IMPLEMENTATION = "2.7"
 TWISTED_REACTOR = "twisted.internet.asyncioreactor.AsyncioSelectorReactor"
 FEED_EXPORT_ENCODING = "utf-8"

scrapy/utils/request.py

@@ -5,6 +5,7 @@ scrapy.http.Request objects
 
 import hashlib
 import json
+import warnings
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -25,6 +26,7 @@ from w3lib.http import basic_auth_header
 from w3lib.url import canonicalize_url
 
 from scrapy import Request, Spider
+from scrapy.exceptions import ScrapyDeprecationWarning
 from scrapy.utils.httpobj import urlparse_cached
 from scrapy.utils.misc import load_object
 from scrapy.utils.python import to_bytes, to_unicode
@@ -139,14 +141,22 @@ class RequestFingerprinter:
                 "REQUEST_FINGERPRINTER_IMPLEMENTATION"
             )
         else:
-            implementation = "2.7"
-        if implementation == "2.7":
+            implementation = "SENTINEL"
+
+        if implementation == "SENTINEL":
+            self._fingerprint = fingerprint
+        elif implementation == "2.7":
+            message = (
+                "'REQUEST_FINGERPRINTER_IMPLEMENTATION' is a deprecated setting.\n"
+                "And it will be removed in future version of Scrapy."
+            )
+            warnings.warn(message, category=ScrapyDeprecationWarning, stacklevel=2)
             self._fingerprint = fingerprint
         else:
             raise ValueError(
                 f"Got an invalid value on setting "
                 f"'REQUEST_FINGERPRINTER_IMPLEMENTATION': "
-                f"{implementation!r}. Valid value is '2.7'."
+                f"{implementation!r}. Valid values are '2.7' and 'SENTINEL'."
             )
 
     def fingerprint(self, request: Request) -> bytes:

scrapy/utils/test.py

@@ -76,7 +76,6 @@ class TestSpider(Spider):
 def get_crawler(
     spidercls: Optional[Type[Spider]] = None,
     settings_dict: Optional[Dict[str, Any]] = None,
-    prevent_warnings: bool = True,
 ) -> Crawler:
     """Return an unconfigured Crawler object. If settings_dict is given, it
     will be used to populate the crawler settings with a project level
@@ -86,8 +85,6 @@ def get_crawler(
 
     # Set by default settings that prevent deprecation warnings.
     settings: Dict[str, Any] = {}
-    if prevent_warnings:
-        settings["REQUEST_FINGERPRINTER_IMPLEMENTATION"] = "2.7"
     settings.update(settings_dict or {})
     runner = CrawlerRunner(settings)
     crawler = runner.create_crawler(spidercls or TestSpider)

tests/test_utils_request.py

@@ -1,5 +1,6 @@
 import json
 import unittest
+import warnings
 from hashlib import sha1
 from typing import Dict, Optional, Tuple, Union
 from weakref import WeakKeyDictionary
@@ -263,6 +264,19 @@ class RequestFingerprinterTestCase(unittest.TestCase):
             fingerprint(request),
         )
 
+    def test_deprecated_implementation(self):
+        settings = {
+            "REQUEST_FINGERPRINTER_IMPLEMENTATION": "2.7",
+        }
+        with warnings.catch_warnings(record=True) as logged_warnings:
+            crawler = get_crawler(settings_dict=settings)
+        request = Request("https://example.com")
+        self.assertEqual(
+            crawler.request_fingerprinter.fingerprint(request),
+            fingerprint(request),
+        )
+        self.assertTrue(logged_warnings)
+
     def test_unknown_implementation(self):
         settings = {
             "REQUEST_FINGERPRINTER_IMPLEMENTATION": "2.5",