natively support Structured Field Values

[Jxck]

What is the feature you are proposing?

Structured Field Values is the standard spec for serialize structured object into http header value.

• RFC 8941: Structured Field Values for HTTP
  • https://www.rfc-editor.org/rfc/rfc8941.html

It already referrered by tons of newly defined http specs.

• References to RFC 8941
  • https://datatracker.ietf.org/doc/rfc8941/referencedby/

And also, IETF HTTP Working Group currently working on retrofit SFV with existing headers.

• Retrofit Structured Fields for HTTP
  • https://httpwg.org/http-extensions/draft-ietf-httpbis-retrofit.html

So we can say it's a best practice to use SFV for headers, not JSON in any headers.
For avoiding developer using JSON or any other format, or SFV like format via hand-made-string-concat, Hono can natively support SFV encoder/decoder and guide developer to use it.

for example.

c.res.headers.append('Cache-Status', 'OriginCache; hit; ttl=1100, "CDN Company Here"; hit; ttl=545')

can be type gurded, by require SFList for value when key is Cache-Status.

c.res.headers.append('Cache-Status',  sfv.encodeList([{
  "value": "Symbol(OriginCache)",
  "params": {
   "hit": true,
   "ttl": 1100
  }
 },
 {
  "value": "CDN Company Here",
  "params": {
   "hit": true,
   "ttl": 545
  }
 }
]))

FYI: I published typed SFV library to npm https://github.com/jxck/structured-field-values

Thanks.

[yusukebe]

Hi @Jxck !

It's very interesting, and your library seems very good. If we implement it, we will add the feature to c.header(). I'll try to investigate the SFV more. Thanks.