Allow json to be called multiple times

[onbjerg]

Consider a wrapper function that calls the json function, while wrapping another function that calls the json function as well, e.g.

const { json } = require('micro')

const wrapper = function (fn) {
  return async function (req, res) {
    console.log('wrapper', await json(req))
    return await fn(req, res)
  }
}

module.exports = wrapper(async function (req, res) {
  console.log('main', await json(req))
  return 'stuff'
})

The call to json by the wrapper would block the next call indefinitely, since the stream from req has already been read.

This PR solves that.

[timneutkens]

@rauchg I monkey patched this in micro-dev. What would you prefer? If it's in micro core, then please do merge 😄

[onbjerg]

@timneutkens It shouldn't be a monkeypatch since it's true for all wrapper functions that need to use json.

[rauchg]

Maybe we should use a WeakMap so that we don't touch req?

[onbjerg]

Where would you store the WeakMap? Just outside the function?

[rauchg]

Yep

[rauchg]

This is a pretty big semantic change. We would have to document it.

[onbjerg]

Sure, I'll document it, too.

[rauchg]

Made a little clarification in the code. Let me know what you think

[onbjerg]

Yeah, I think it makes sense to add a comment to clarify what's happening. I'm fixing the test.

[onbjerg]

I documented the behavior. Any thoughts?

[timneutkens]

Looks good 👍

[timneutkens]

Thing I'm wondering, should we add a rawBody or body function now. To expose the cache to external modules. We've been holding off on this since it would be possible without (https://github.com/timneutkens/raw-text).

[onbjerg]

@timneutkens You can read the raw body with other modules from the request, since bodies can be formatted in different ways and thus are parsed differently. I don't think having a body function would serve any purpose

But maybe I'm wrong

[timneutkens]

Yeah it's just the case of calling json on it and then urlencoded on it for example, where it would fail because the body was already parsed. It's an edge case though, I don't mind not supporting it.

[onbjerg]

@timneutkens Is it even possible to have multiple bodies in the same request? I don't think I'm following

[timneutkens]

I was explaining a pretty far fetched use case where you'd want to do something with the request body if json parsing fails. But nvm that, it's not important 👍