encode/httpx#1214 prefer sending outbound cookies separately to improve headers compression

Author: cdeler

src/h2/utilities.py

@@ -603,6 +603,30 @@ def _combine_cookie_fields(headers, hdr_validation_flags):
         yield NeverIndexedHeaderTuple(b'cookie', cookie_val)
 
 
+def _split_outbound_cookie_fields(headers, hdr_validation_flags):
+    """
+    RFC 7540 § 8.1.2.5 allows for better compression efficiency,
+    to split the Cookie header field into separate header fields
+
+    We want to do it for outbound requests, as we are doing for
+    inbound
+    """
+    for header in headers:
+        if header[0] in (b'cookie', 'cookie'):
+            needle = b'; ' if isinstance(header[0], bytes) else '; '
+
+            if needle in header[1]:
+                for cookie_val in header[1].split(needle):
+                    if isinstance(header, HeaderTuple):
+                        yield header.__class__(header[0], cookie_val)
+                    else:
+                        yield header[0], cookie_val
+            else:
+                yield header
+        else:
+            yield header
+
+
 def normalize_outbound_headers(headers, hdr_validation_flags):
     """
     Normalizes a header sequence that we are about to send.
@@ -611,6 +635,7 @@ def normalize_outbound_headers(headers, hdr_validation_flags):
     :param hdr_validation_flags: An instance of HeaderValidationFlags.
     """
     headers = _lowercase_header_names(headers, hdr_validation_flags)
+    headers = _split_outbound_cookie_fields(headers, hdr_validation_flags)
     headers = _strip_surrounding_whitespace(headers, hdr_validation_flags)
     headers = _strip_connection_headers(headers, hdr_validation_flags)
     headers = _secure_headers(headers, hdr_validation_flags)

test/test_basic_logic.py

@@ -9,6 +9,7 @@
 
 import hyperframe
 import pytest
+from hpack import HeaderTuple
 
 import h2.config
 import h2.connection
@@ -789,6 +790,47 @@ def test_headers_are_lowercase(self, frame_factory):
 
         assert c.data_to_send() == expected_frame.serialize()
 
+    def test_outbound_cookie_headers_are_split(self):
+        """
+        We should split outbound cookie headers according to
+        RFC 7540 - 8.1.2.5
+        """
+        cookie_headers = [
+            HeaderTuple('cookie',
+                        'username=John Doe; expires=Thu, 18 Dec 2013 12:00:00 UTC'),
+            ('cookie', 'path=1'),
+            ('cookie', 'test1=val1; test2=val2')
+        ]
+
+        expected_cookie_headers = [
+            HeaderTuple('cookie', 'username=John Doe'),
+            HeaderTuple('cookie', 'expires=Thu, 18 Dec 2013 12:00:00 UTC'),
+            ('cookie', 'path=1'),
+            ('cookie', 'test1=val1'),
+            ('cookie', 'test2=val2'),
+        ]
+
+        client_config = h2.config.H2Configuration(
+            client_side=True,
+            header_encoding='utf-8'
+        )
+        server_config = h2.config.H2Configuration(
+            client_side=False,
+            normalize_inbound_headers=False,
+            header_encoding='utf-8'
+        )
+        client = h2.connection.H2Connection(config=client_config)
+        server = h2.connection.H2Connection(config=server_config)
+
+        client.initiate_connection()
+        client.send_headers(1, self.example_request_headers + cookie_headers, end_stream=True)
+
+        e = server.receive_data(client.data_to_send())
+
+        cookie_fields = [(n, v) for n, v in e[1].headers if n == 'cookie']
+
+        assert cookie_fields == expected_cookie_headers
+
     @given(frame_size=integers(min_value=2**14, max_value=(2**24 - 1)))
     @settings(suppress_health_check=[HealthCheck.function_scoped_fixture])
     def test_changing_max_frame_size(self, frame_factory, frame_size):