Proxy - Set Cookie headers are merged causing them to not work

[zilinjak]

Set-Cookie headers do get merged, which leads that only 1st cookie is set in browser. Set-Cookie header CAN'T be merge into single header according to RFC 6265

Current Behavior

Set-Cookie: user=example_value; Path=/
Set-Cookie: not-present=example_value; Path=/

will ended up as

set-cookie: user=example_value; Path=/,not-present=example_value; Path=/

Expected Behavior

Set-Cookie headers are preserved and NOT merged.

Possible Workaround/Solution

Not yet discovered

Steps to Reproduce

1. Start python HTTP server that returns 2 cookies

import http.server
import socketserver

class MyRequestHandler(http.server.SimpleHTTPRequestHandler):
    def do_GET(self):
        self.send_response(200)
        self.send_header("Content-type", "text/html")
        self.send_header("Set-Cookie", "user=example_value; Path=/")
        self.send_header("Set-Cookie", "not-present=example_value; Path=/")
        self.end_headers()
        self.wfile.write(b"Hello, world! You've got a cookie.")

port = 8081
with socketserver.TCPServer(("", port), MyRequestHandler) as httpd:
    print(f"Serving on port {port}")
    httpd.serve_forever()

2. Curl server directly

curl -v localhost:8081

here you can see that the 2 set-cookie headers are present

3. Start prism proxy and point it to localhost:8081
4. Curl again but the proxy at localhost:4010

curl -v localhost:4010

Output will be

set-cookie: user=example_value; Path=/,not-present=example_value; Path=/

which is incorrect