User-configurable headers: (was Re: Call for objections releasing 0.10)

[Curt Arnold <ca...@apache.org>]

On Sep 17, 2009, at 12:39 AM, Paul Davis wrote:
>> I'm not sure how to interpret that statement.  I'd like to  
>> interpret as an
>> willingness to consider for configurable headers.
>
> Absolutely! Its on my whiteboard. Configurable headers are an
> excellent solution here because they're a generic feature that can be
> used to solve the issue at hand. As much as I dislike adding hacks for
> specific user agents, I do like adding generic capabilities to allow
> flexibility.
>
> HTH,
> Paul Davis



One issue to be noted is that if multiple values for the same header  
appear in the call to mochiweb, they will be merged into a comma  
separated list.  It is a good feature, except when you have header  
attributes that are mutually exclusive or inconsistent.  In my Expires  
patch, I had to remove the Expires header from the uuid code in order  
not to have comma separated list of dates.

What I think that would mean is you might do the equivalent of changing:

send_json(Req, Code, Value) ->
     send_json(Req, Code, [], Value).

send_json(Req, Code, Headers, Value) ->
     DefaultHeaders = [
         {"Content-Type", negotiate_content_type(Req)},
         {"Cache-Control", "must-revalidate"},
         {"Expires", "Fri, 01 Jan 1990 00:00:00 GMT"}
     ],
     Body = list_to_binary(
         [start_jsonp(Req), ?JSON_ENCODE(Value), end_jsonp(), $\n]
     ),
     send_response(Req, Code, DefaultHeaders ++ Headers, Body).

to:

send_json(Req, Code, Value) ->
     DefaultHeaders = [
         {"Content-Type", negotiate_content_type(Req)},
         {"Cache-Control", "must-revalidate"},
         {"Expires", "Fri, 01 Jan 1990 00:00:00 GMT"}
     ],
     send_json(Req, Code, DefaultHeaders, Value).

send_json(Req, Code, Headers, Value) ->
     Body = list_to_binary(
         [start_jsonp(Req), ?JSON_ENCODE(Value), end_jsonp(), $\n]
     ),
     send_response(Req, Code, Headers, Body).


Which would mean that any code that wants to provide non-default  
headers (other than the calculated Date, etc) is responsible for  
assembling the full list of headers.  Last I checked, only the uuid  
code called the 4 parameter send_json, but that might have changed.