Redesign serve() and mutate() apis, and maybe getEntry too

[dai-shi]

There are a few things of my concern:

• serve() caches too much how to get current pathname in server component? #84
• refetch on rerender might not be the best
• props serialization is tricky
• mutate() can only return one tree
  • Just noticed https://github.com/facebook/react/blob/997f52fbb30ec4b777b66edcdd75f594d9fe0c55/fixtures/flight/src/index.js#L19 returning multiple values
• getEntry() might not be the best
  • Should we expect to use lazy?

[dai-shi]

New protocol idea (1st iteration)

Request

GET /RSC/<input string>

For callServer:

POST /RSC/<id string>

Response

Promise<{
  value?: unknown
  elements?: { [id: string]: JSXStream },
}>

---

Current protocol (v0.14.0)

Request

GET /RSC/<id string>/props=<JSON stringified props>

For callServer:

POST /RSC/_/action_id=<string>

Response

JSXStream or value

[dai-shi]

2nd iteration

// Request
GET /RSC/<input string>
POST /RSC/<action id string>

// Response
Promise<{
  v?: unknown // for value
  t?: { [element id string]: JSXElementStream }
}>

// entries.tsx
function render(input: string): Promise<{ [element id string]: JSXElement }>

(Hmm, this doesn't allow "patching"... 🤔 )

[dai-shi]

3rd iteration

// Request
GET /RSC/<input string>
POST /RSC/<action id string>

// Response
Promise<{
  _value: unknown
  [element id string]: JSXElementStream
}>

// entries.tsx
function render(input: string, options: unknown): Promise<{
  [element id string]: JSXElement // element id shouldn't be `_value` or maybe any `_*`
}>

will drop mutate() on client, and introduce rerender(input: string) on server. not sure how to implement serve() yet.

[dai-shi]

3rd iteration

I'm thinking to implement it.