Support cookies with value `None`

[tducret]

Summary

There are 3 kinds of request cookie headers.

request = httpx.Request("GET", "https://www.example.org", cookies=cookies)
request.headers["cookie"]  # <== This is the request cookie header we are talking about here

"name=value"

This is the classic case, already supported through :

cookies.set(name="name", value="value", domain="example.org")

"name="

Please note the trailing = sign here. This is also supported, by passing an empty string as the cookie value :

cookies.set(name="name", value="", domain="example.org")

"name"

Please note there is no trailing = sign here. This is not officially supported (yet), but can be achieved with :

cookies.set(name="name", value=None, domain="example.org")

It works because the cookie jar implementation in the standard library already deals with it. Contrary to the httpx.Cookies.set method, the standard Cookie doesn't define strict typing for the value.

So this PR changes the httpx._models in order to support a cookie value which is None. Otherwise the typing is incorrect, forcing the httpx to add a # type: ignore instruction.

The getter functions had to be updated as well, as the None was considered as a not found value.

2 new test cases are added in this PR to ensure the proper behavior.

Checklist

• [X] I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• [X] I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• [ ] I've updated the documentation accordingly.

[tducret]

Is there anything else I can do before we merge it to the main branch?

[lovelydinosaur]

Do name= and name have the same behavior?...

[tducret]

Do name= and name have the same behavior?...

According to the RFC for HTTP protocol :

If the name-value-pair string lacks a %x3D ("=") character, then the name string is empty, and the value string is the value of name-value-pair.

So it may depend on the server implementation, but I can confirm a case where the server considered name= and name as different. Although this was already possible to create both kinds of cookies, this PR confirms this usage by changing the type hint.