Use a ReadableStream with byte source (formerly called ReadableByteStream) for .body

[tyoshino]

/cc @yutakahirano

ReadableByteStream has been merged into ReadableStream interface. It's time to update the ReadableStream section of the Fetch spec (https://fetch.spec.whatwg.org/#readablestream) to adopt the updated ReadableStream and construct a ReadableStream with the byte handling feature (i.e. getReader() returns a ReadableStreamBYOBReader when a certain option is passed).

In the first step, we don't need to fully use the BYOB responding API but may just call the same enqueue() method.

[youennf]

Currently the fetch spec allows constructing a Response with any ReadableStream, which can thus be enqueued with ArrayBuffers, Uint8Arrays or potatoes.

Restricting the Response body to a ReadableStream with a byte source would remove the possibility to enqueue potatoes, leaving space for ArrayBuffer and ArrayBufferView.

But enqueuing something else than Uint8Array would still lead to TypeError when consuming the body, since "read all bytes" requires Uint8Array objects.
Can we remove that restriction?
That would make it consistent with the possibility to create a Response with whatever ArrayBuffer/ArrayBufferView.

[annevk]

I thought we wanted to require Uint8Array?

[domenic]

Yeah, a while ago we discussed whether we should perform some auto-conversion from array buffer views or blobs or strings, and decided to settle on being conservative and just allowing Uint8Array. I think the discussion was at yutakahirano/fetch-with-streams#53.

[youennf]

"read all bytes" is not really doing any conversion, it merely appends a Uint8Array to a byte sequence. Any BufferSource would be as easily appendable there.

I do not see what is gained with this restriction.
I can see how inconsistent it might be if Response gets restricted to a byte ReadableStream.

yutakahirano/fetch-with-streams#53 seems mostly about upload.

[annevk]

Yeah, though a Response object created in a service worker feeding a document/worker API is very similar to upload. I think we should try to keep them consistent.

[annevk]

@yutakahirano is this fixed?

[yutakahirano]

Not yet.

[ricea]

This might not happen quickly, as we want to run an experiment in Chrome to ensure it is web-compatible to use a byte stream. In theory there is no problem, but AFAIK it's never been tested and it's not something we can afford to break.