Multiple headers with same name should be treated as a list

[rahmansyed]

I'd like to submit for consideration handling of multiple HTTP headers with the same name. Currently, it appears that falcon is selecting one of the values while discarding the remainder.

http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2

Multiple message-header fields with the same field-name MAY be present in a 
message if and only if the entire field-value for that header field is defined as a comma-
separated list [i.e., #(values)]. It MUST be possible to combine the multiple header 
fields into one "field-name: field-value" pair, without changing the semantics of the 
message, by appending each subsequent field-value to the first, each separated by a 
comma.

In particular, this issue is arising with a newer version of Repose which splits any of its internal headers that are comma delimited.

[kgriffs]

The trick with this is doing it in an efficient way. Let me take a stab at it.

[kgriffs]

@rsyed83 You are talking specifically about accessing multiple headers from the req object, right?

[kgriffs]

OK, so I looked into this and not sure why I didn't think of this off the bat, but the WSGI environ is a dict, and so it cannot hold duplicate header names in it. I tested wsgiref, gunicorn, and uwsgi. The first two combined the duplicate header lines into a comma-delimited string. However, uwsgi only retained the last headervalue.

@rsyed83 Are you running uwsgi?

[jarretraim]

@kgriffs We are running uwsgi in barbican and we're seeing this too. Seems like it might be their bug?

[rahmansyed]

@kgriffs yeah we're using uwsgi as well. Thanks for looking into it from the falcon perspective, didn't realize it'd be something handled in the layer above.

[kgriffs]

Glad to help! Please let me know if you are able to confirm this is a uwsgi bug.

[jfwood]

I'll ask the uWSGI list about this one.

[jfwood]

Per ever-responsive Robert De Ioris with uWSGI:

This patch adds support for combining headers when in native http mode:
unbit/uwsgi@8a032b4

Regarding when this patch might be released, he mentioned:
We have 2 bugs still opened, once fixed we will release 2.0.4. If all goes
well it should happen in a couple of days.

[kgriffs]

Cool, thanks for following up with the uWSGI folks!

[kgriffs]

Closing this bug since it isn't Falcon's.