Fix _get_encoding_or_mime_type_from_headers handling on comma-separated Content-Encoding values

scrapy/utils/response.py

@@ -83,7 +83,10 @@ def _get_encoding_or_mime_type_from_headers(
     headers: Headers,
 ) -> Tuple[Optional[bytes], Optional[bytes]]:
     if b'Content-Encoding' in headers:
-        encodings = headers.getlist(b'Content-Encoding')
+        encodings = [
+            item.strip() for item in
+            b",".join(headers.getlist(b'Content-Encoding')).split(b",")
+        ]
         if encodings:
             return encodings[-1], None
     if (

tests/test_utils_response.py

@@ -19,6 +19,7 @@ from scrapy.utils.response import (
     open_in_browser,
     response_httprepr,
     response_status_message,
+    _get_encoding_or_mime_type_from_headers,
 )
 
 
@@ -643,6 +644,26 @@ def test_get_response_class_http(kwargs, response_class):
     assert get_response_class(**kwargs) == response_class
 
 
+@pytest.mark.parametrize(
+    'headers,expected',
+    (
+        *(
+            (
+                Headers({'Content-Encoding': content_encoding_header}),
+                (encoding, None),
+            )
+            for content_encoding_header, encoding in (
+                (['gzip'], b'gzip'),
+                (['gzip', 'compress'], b'compress'),
+                (['deflate, br'], b'br'),
+            )
+        ),
+    ),
+)
+def test_get_encoding_or_mime_type_from_headers(headers, expected):
+    assert _get_encoding_or_mime_type_from_headers(headers) == expected
+
+
 class ResponseUtilsTest(unittest.TestCase):
     dummy_response = TextResponse(url='http://example.org/', body=b'dummy_response')