feature request(streams): lines(readable): AsyncIterable<string>

[kt3k]

Idea from some discussion: A quick helper for getting an async iterable (or maybe another stream) of lines from a ReadableStream.

Example signature: lines(readable: ReadableStream<Uint8Array>|ReadableStream<string>): AsyncIterable<string>

import { lines } from "@std/streams";

const file = await Deno.open(filename);
for await (const line of lines(file.readable)) {
  console.log(line);
}

[BlackAsLight]

Does this not already exist via TextLineStream?

import { TextLineStream } from '@std/streams'

for await (
  const line of (await Deno.open('./deno.json'))
    .readable
    .pipeThrough(new TextEncoderStream())
    .pipeThrough(new TextLineStream())
)
  console.log(line)

[iuioiua]

I'm impartial to adding this. The above code snippet using TextLineStream() seems to suffice.

[kt3k]

import { TextLineStream } from '@std/streams'

for await (
  const line of (await Deno.open('./deno.json'))
    .readable
    .pipeThrough(new TextEncoderStream())
    .pipeThrough(new TextLineStream())
)
  console.log(line)

The above example is correct, but it looks a bit cluttered for such typical simple task, compared to other languages/runtimes.

Reading lines from a file is much simpler in other languages.

python

file = open('README.md', 'r')
for line in file.readlines():
  print(line)

perl

open(INFO, "README.md") or die();
foreach $line (<INFO>)  {   
  print $line;    
}

I think it would be useful to have special/ergonomic wrapper for such typical task

[BlackAsLight]

If something like this is to be added, I think a toLines(stream) to align with toText and toJSON would be best. Although on the other hand somebody might assume it would return an iterable of strings instead of an async iterable of strings.

[kt3k]

toLines sounds good to me

[jsejcksn]

I agree with the comment by @iuioiua — this seems convenient, but also somewhat trivial.

If it is decided to be added, I think that the return type should be ReadableStream<string> to provide more convenience value: it already implements AsyncIterable<string> and can also be piped, etc.