Get fingerprint function through crawler, import legacy function othe…

…rwise

scrapy_deltafetch/middleware.py

@@ -30,7 +30,17 @@ def __init__(self, dir, reset=False, stats=None, crawler=None):
         self.dir = dir
         self.reset = reset
         self.stats = stats
-        self.fingerprint=RequestFingerprinter(crawler).fingerprint
+        if crawler and hasattr(crawler, 'request_fingerprinter'):
+            self.fingerprint=crawler.request_fingerprinter.fingerprint
+        else:
+            try:
+                # compatibility with Scrapy <2.7.0
+                from scrapy.utils.request import request_fingerprint
+                self.fingerprint=request_fingerprint
+            except ImportError:
+                # use the new default 
+                from scrapy.utils.request import fingerprint
+                self.fingerprint=fingerprint
 
     @classmethod
     def from_crawler(cls, crawler):

tests/test_deltafetch.py

@@ -9,11 +9,17 @@
 from scrapy.spiders import Spider
 from scrapy.settings import Settings
 from scrapy.exceptions import NotConfigured
-from scrapy.utils.request import RequestFingerprinter
 from scrapy.utils.python import to_bytes
 from scrapy.statscollectors import StatsCollector
 from scrapy.utils.test import get_crawler
 
+try:
+    from scrapy.utils.request import request_fingerprint
+    _legacy_fingerprint=True
+except ImportError:
+    from scrapy.utils.request import RequestFingerprinter
+    _legacy_fingerprint=False
+
 from scrapy_deltafetch.middleware import DeltaFetch
 
 
@@ -319,7 +325,10 @@ def test_get_key(self):
         mw = self.mwcls(self.temp_dir, reset=True)
         test_req1 = Request('http://url1')
         crawler = get_crawler(Spider)
-        fingerprint=RequestFingerprinter(crawler).fingerprint
+        if _legacy_fingerprint:
+            fingerprint=request_fingerprint
+        else:
+            fingerprint=RequestFingerprinter(crawler).fingerprint
         self.assertEqual(mw._get_key(test_req1),
                          to_bytes(fingerprint(test_req1)))
         test_req2 = Request('http://url2', meta={'deltafetch_key': b'dfkey1'})