When multiple headers have the same key, only one is preserved

[mottersheadt]

Problem or feature statement

input.headers does not support multi-dict. If there are 2 Set-Cookie headers in an HTTP response, the second one gets deleted.

Advised solution

We should use the multi-dict feature in Larky to support having multiple headers with the same key.

[mahmoudimus]

input.headers should return a list of tuples. If you want to use multidict, then you can just multidict(input.headers).

Does that work for you?

[mottersheadt]

I'll test. Currently the headers can be referenced like this: input.headers['header-name']. Are you saying that under the hood it's actually a list of tuples, and the dictionary reference method is just syntactic sugar?

[mahmoudimus]

No, I mean the ask here is that you want headers back as a multidict instead of a list of tuples. I am saying, if you want multidict, then just pass the list of tuples into the multidict instead of expecting headers to come back as a multidict by default :)

[mottersheadt]

Ah - I was misunderstanding the structure. I thought the headers were already a dictionary. Calling mutlidict should work. I'll let you know if I hit any blockers.

[mahmoudimus]

@mottersheadt this needs to be re-opened because input.headers needs to return a list of tuples. It does not right now.

[mottersheadt]

Ok. Won't it be dangerous to switch it to a list of tuples at this point? Everyone who has currently implemented Larky scripts using the header dictionary will have their routes break. I think moving it to a multi-dictionary would be more backwards compatible.

[mahmoudimus]

It depends which FCO, I think.

[mottersheadt]

Here is the current syntax for github.com/verygoodsecurity/common/compute/larky/http/Process. Need to make sure we don't break how it currently works.

                    def process(input, ctx):
                      if 'Authority' in input.headers:
                        input.headers['Authority'] = re.sub('new-test.com', 'test.com', input.headers['Authority'])
                      
                      return input