api.fetch - Add body option ReadableStream support data to fetch

[flaki]

What type of issue is this?

Missing compatibility data

What information was incorrect, unhelpful, or incomplete?

The documentation for the body option lists ReadableStream objects as a valid source of the body contents, but this seems to be unimplemented in most browsers today.

It would perhaps make sense to put a note in the body option description, and maybe even track the support for this feature in a compat table entry?

Edit: As the related issue #13854 mentions, the support (or lack thereof) is correctly tracked on the Request page compat tables, so I believe this can be just resolved through getting a note into the main fetch() page.

What browsers does this problem apply to, if applicable?

Chromium (Chrome, Edge 79+, Opera, Samsung Internet), Firefox

What did you expect to see?

That the documentation provides information whether ReadableStream objects can be used safely in browsers today to provide body content for fetch() requests.

Did you test this? If so, how?

(await fetch('https://httpbin.org/post', {
	method: 'POST',
	body: (await fetch('https://pokeapi.co/api/v2/pokemon/pikachu')).body
})).json()

Note that the posted data is the string "[object ReadableStream]", and not the JSON data returned from the embedded fetch.

Can you link to any release notes, bugs, pull requests, or MDN pages related to this?

• https://developer.mozilla.org/en-US/docs/Web/API/fetch#body
• https://developer.mozilla.org/en-US/docs/Web/API/Response/body

Do you have anything more you want to share?

No response

MDN URL

https://developer.mozilla.org/en-US/docs/Web/API/fetch

MDN metadata

MDN page report details

• Query: api.fetch
• Report started: 2022-07-01T07:09:38.163Z