Dicer hangs when used with `stream/promises`' `pipeline`

[indutny-signal]

Test case:

const { Readable } = require('stream');
const { pipeline } = require('stream/promises');
const Dicer = require('dicer');

async function main() {
  const r = new Readable({ read() {} });
  const d = new Dicer({ boundary: 'a' });

  d.on('part', async (part) => {
    part.resume();
  });

  r.push(`--a\r\nA: 1\r\nB: 1\r\n\r\n123\r\n--a\r\n\r\n456\r\n--a--\r\n`);
  setImmediate(() => {
    r.push(null);
  });

  const timer = setTimeout(() => {
    throw new Error('Should be canceled');
  }, 2000);

  await pipeline(r, d);

  clearTimeout(timer);
}

main();

[indutny-signal]

Investigated it and the issue appears to be the this.emit('finish') call when the part ends (end event). Apparently, the readable stream in this example never ends because the destination is unpiped before the 'end' event happens. In other words, we didn't quite finish writing yet, but Dicer happily reported that we did.

[mscdex]

This module is due for a rewrite now that node should have all of the necessary hooks to accomplish what the hacks were previously doing. I'm not sure when that will happen though.

[indutny-signal]

@mscdex I think I'm about to do that in TypeScript. Would you be interested in me contributing it back?

[indutny-signal]

More importantly, what ideas do you have for an API? Object mode streams instead of part event?

[mscdex]

What I had in mind was just removing the event hacks, using ES6 Classes, and other code cleanup (that doesn't cause noticeable performance regressions).... nothing breaking.

[indutny-signal]

Sounds good. I think I could try doing that, if you don't mind me submitting a PR.

[mscdex]

Have at it.

[indutny-signal]

@mscdex it turned out to be less complicated than I thought it would be: https://github.com/mscdex/dicer/pull/27