Set-Cookie header not set properly when cookies are modified

[Speedlulu]

Problem Description

Described here #5084

Steps to reproduce the behavior:

1. Have a server set a cookie with en empty attributes (Secure, HttpOnly ...)
2. Edit CookieAttrs object of said object
3. Assign (value, CookieAttrs) tuple to the flow.response.cookies object
4. Response header will now have empty attribute in Set-Cookie header set as Secure=; HttpOnly=

System Information

Mitmproxy: 7.0.4
Python: 3.8.10
OpenSSL: OpenSSL 1.1.1l 24 Aug 2021
Platform: Linux-5.11.0-46-generic-x86_64-with-glibc2.29

Pull request

I have created a pull request (#5084) to try to fix the issue, it works well for my use but it might break parts of the app that I'm not aware and/or don't use.

[mhils]

Thank you for the clear report. Your PR looks great on first sight, it just may take me a bit before I find some time to dig into the relevant parts of the codebase and see if this breaks anything. 👍

[Speedlulu]

Alrighty let me know if you need anything along the way :)

[Prinzhorn]

While searching for something entirely unrelated I randomly came across #1512 which I think refs this and can be closed after the PR is merged? It also points towrds HAR dump, so maybe the contrib example addon is affected by this change as well.

[Speedlulu]

@Prinzhorn This is indeed while working with SameSite cookies that I ran into this problem.

[Speedlulu]

I updated the PR :)

[Prinzhorn]

@mhils can this issue and #1512 be closed now?

[mhils]

Yes, but also feel free to just close things if you think they should be closed! 😄