Hint that using `data` is wrong

From time to time i see ppl using data instead of body which is wrong. happened just recently in https://github.com/node-fetch/node-fetch/issues/481#issuecomment-717864624

how do you feel about adding a little warning message that can only appear once. (kinda like node reports that you are using experimental apis)

if ('data' in bodyInit && notWarned) {
  console.warn('use body instead')
}
class Response {
  get data () {
    notWarned && console.warn('you want to use .json(), .text(), .arrayBuffer() or just .body')
  }
}

I don’t think it is uncommon to see those mistake happening when switching from different request libraries axios use data instead of body for example. I can admit that i have used data as well and wasted minutes trying to figure out what’s wrong

[jimmywarting]

Yay, i claimed issue 1000 🎉

[jimmywarting]

It’s a good idea, but I’m not sure how far we should deviate from the original fetch spec.

it’s not like we are adding any new feature/method into fetch, it’s just a way of helping/notifying that what you might be doing is wrong. such notification could easily be removed if we ever decide to ditch it again