feat: simulate body events

[farnabaz]

This PR create a simple simulation for body streaming based on https://github.com/unjs/h3/issues/29#issuecomment-891951452

resolves unjs/node-mock-http#8

[farnabaz]

process.nextTick is important here, this is necessary to postpone emit call and make sure listeners are set.

[danielroe]

This won't work in a non-Node environment, even with the unenv process polyfill. Is there another way to implement this?

[farnabaz]

I think createCall is deeply depends on node environment, because IncomingMessage extends Readable and it extends Node's EventEmitter import { EventEmitter } from 'events'

As for process.nextTick, we need a way to ensure listeners are set, as a solution we can implement EventEmitter logic and create a delayed emit.

[pi0]

We can probably use defer polyfill but seems actual readable implementation waits for first listener to drain data: https://github.com/nodejs/node/blob/master/lib/internal/streams/readable.js#L311

[pi0]

We can use newListener event too or spy on prototype method (https://github.com/nodejs/node/blob/602fe4e83a572359c08c3a28fe054addb4252153/lib/internal/streams/readable.js#L902)

[pi0]

@danielroe While not related, i'm curious why polyfill not working? It seems has polyfill for nextTick too (https://github.com/defunctzombie/node-process/blob/77caa43cdaee4ea710aa14d11cea1705293c0ef3/browser.js#L134)

[pi0]

(closing since timeout is not a good solution. since having workaround, let's redo it later and track in linked issue)