feat(Body): Added support for BodyMixin.formData() and constructing bodies with FormData

[jimmywarting]

Purpose

• Add support for both response.formData() and request.formData()
• Support constructing not only new Request(url, {body: formData}) but also new Response(formData) as it's supposed to be (only supported Request before...)
• It's also able to convert a URLSearchParam to a formData as it dose in browser/spec

This would be a great addition so you can avoid having to depend on some external multiparty, formidable, busboy or any other body parser packages. that all have some different (non-speced) apis that you would need to learn.
Instead you could just do:

import { Response } from 'node-fetch'

http.createServer(async function (req, res) {
  const formData = await new Response(req, { headers: req.headers }).formData()
  const file = formData.get('avatar')
  
  var arrayBuffer = await file.arrayBuffer()
  var text = await file.text()
  var whatwgReadableStream = file.stream()
}) 

Changes

• I changed the FormData test file to test more end to end instead.
• Added a fast algoritm to parse formData

Additional information

Maybe thinking it would be nice to expose FormData, Blob and File from index.js so they are accessible, thoughts?
Think we have had this discussion before with exposing Blob before... #392

---

• I updated ./docs/CHANGELOG.md
• I updated readme
• I added unit test(s)

---

closes #199
closes #1118
closes #1293
closes #876

[jimmywarting]

Ready to be reviewed...

all fixed

[LinusU]

@jimmywarting seems to be a conflict in package.json, could you fix that?

@Richienb would you be able to review this? ☺️

[jacob-ebey]

Oh this is exciting. Can't wait to see this merged.

[tunnckoCore]

Hi there, one of the two formidable maintainers last years. @felixge, the author, passed the torch while back.
Happy to see his legacy merged into some even bigger module. Didn't knew it was merged until today. File and FormData stadnardization is great addition.

Still think that @jimmywarting should have added 1-2 lines of attribution and license, it's not that different than the current latest (v2) on npm. The v1 one was pure and just the parser, then for v2 we made it Transform stream for some reason. But I like this clean Uin8Array variant more, so I'll really extract it as formidable-multipart or something like that, thought for decoupling Formidable for quite some time, and v3-v4 is where it can come.

We already discussed some modern APIs for v3 node-formidable/formidable#635

[jimmywarting]

Still think that @jimmywarting should have added 1-2 lines of attribution and license,

yea, sorry about that.
Can ofc add some 1-2 lines of attribution and license.

@jimmywarting ha, didn't knew that node-fetch is using formidable's multipart parser, hehe.

The only difference is that it's not Transform stream and uses uint8array. Seems like it also expose toFormData which is exactly what I thought in my previous comment LOL - thin layer on top of the parser.

Do you mind to extract it as @formidable/multipart and we will both use it? Not sure if the namespace is free.

Yep, it was based on an older PR i made specifically for https://github.com/github/fetch a long time ago that dose not bring in node:streams or node:buffer as a dependency. it's was more cross compatible that way.

it kind of also has to work with the new whatwg streams, so that is why it's based on iterators instead. to support for both whatwg stream and node streams.

---

That think i made in fetch-blob recently about writing files to a temporary location on the disk and then deleting it afterwards... i was think about using createTempFile(iterable, name, opts) instead of using new File()

---

Maybe like the idea of a separated module that is solo about parsing multipart payloads according to web specification. Would you like to create a new repo and maybe add me as a member?