Canonic header field capitalization does not work with all existing headers titles out of the box

[johnd0e]

The issue is that the list in headers.lua is finite and cannot accommodate all possible header values. For instance, it does not include the commonly used header "Origin." I understand that keeping this list updated is challenging, especially given the existence of headers like "X-*-*."

Currently, the options are either to ignore this limitation (as most services handle lower-cased headers well) or to manage the headers manually.

My suggestion is to avoid storing headers altogether and instead normalize them on-the-fly. The existing socket.headers table could remain in place and serve as a cache.

[Tieske]

You can add a metatable with an __index method, it would get called if a header doesn't exist in the table. In that case, normalize it once, and update the table.

[johnd0e]

That is exactly what I mean.
Sholdn't that be implemented in socket.headers.canonic instead of static table?

[Tieske]

Either way, using this table would be like a "warmed-up cache".

A PR to add it is most appreciated. Prior art: https://github.com/ledgetech/lua-resty-http/blob/master/lib/resty/http_headers.lua