Implement bytes_stream() for wasm.

[dmeijboom]

Adds support of Response.bytes_stream() to the wasm32 target.

Follow up of: #1576
Fixes #1704

Todo:

• Testing with our Yew based application (will do that tomorrow)

[seanmonstar]

I think a question I always had with this PR was what are the consequences of pulling in that crate. Sometimes wasm things surprise me. Are there any concerns that we should know about? Like does it require more specific wasm targets? Or if we change the dependency later, would that cause people issues?

[frewsxcv]

I'm not aware of any concerns pulling in the wasm-streams crate. It solely supports wasm32-unknown-unknown, just like reqwest does (as far as I know). This wasm-streams API is not exposed in any way so removing it in the future would not be a breaking change.

[dmeijboom]

I think a question I always had with this PR was what are the consequences of pulling in that crate.

The wasm-streams crate maps ReadableStream -> Stream and WritableStream to Sink. This is neat as we can keep the code similar to the non-wasm implementation. I couldn't find other libraries that are able to do this and it seems like the crate is at least somewhat mature (not a lot of open issues, tested on chrome & firefox, proper documentation etc.).

Sometimes wasm things surprise me.

Me too... 😅

Are there any concerns that we should know about? Like does it require more specific wasm targets? Or if we change the dependency later, would that cause people issues?

I think it should be fine. It supports wasm32-unknown-unknown which is what reqwest also supports. Also note that the return type is a Rust stream so even if we have to make changes later it shouldn't be breaking for reqwest wasm users as it's only used internally (right?).

[seanmonstar]

Alrighty, thanks for clarifying! We can merge, though looks like CI is grumpy.

[dmeijboom]

Alrighty, thanks for clarifying! We can merge, though looks like CI is grumpy.

Indeed. There was also an issue with imports that should only be imported if the stream feature is enabled. Fixed that as well!

Edit: tested this branch with our Yew app and that seems to work!