suggestion: re-consider the deprecation of some IO-related APIs

[iuioiua]

std/io is being deprecated because the Deno.Reader interface and friends are being deprecated from the runtime. However, their read(), write(), and other methods on I/O-related APIs, such as Deno.FsFile and Deno.Conn, are here to stay. These methods staying around justify keeping some IO-related APIs within the Standard Library instead of deprecating them.

To keep the Standard Library and its maintenance lean, I suggest we keep APIs that allow converting Readers and Writers to streams. This will need some more review, but, at first glance, I think we should un-deprecate:

• readAll()
• readableStreamFromReader()
• writeAll()
• writableStreamFromWriter()

CC @bartlomieju, @piscisaureus and @kt3k

[kt3k]

This makes sense to me as Web Stream doesn't completely cover what Reader(Sync)/Writer(Sync)/Closer does.

[kt3k]

@ry What do you think?

[iuioiua]

I've created #4128 to see what this could look like.

[bartlomieju]

Discussed with the CLI team and everyone agrees that it makes sense to keep these APIs in deno_std.

[kt3k]

I often saw people find BufReader BufWriter useful (I haven't used them though). Maybe those are also worth re-introduced?

[iuioiua]

I think there's an argument for Buffer, which, IIUC, is more general-purpose with read and write capabilities.

Doing so, I think, would cover all the most basic modalities for these I/O interfaces and methods (read, write, copy and store).