stream-errors.js

import {Readable} from 'stream';

class ReadableStream extends Readable {
  constructor() {
    super({objectMode: true});
  }

  _read() {
    this.emit('error', 'Error');
  }
}

// This is weird: Node doesn't die and also doesn't throw. 
async function one() {
  try {
    const stream = new ReadableStream();
    for await (const chunk of stream) {}
  } catch(e) {
    // Doesn't get here
    console.log(e)
  }
}
one();

// Error callback gets triggered as expected.
// Catch not reached as expected.
// But now we have a callback we need to handle somehow.
async function two() {
  try {
    const stream = new ReadableStream();

    stream.on('error', () => {
      console.log('Gets here');
    });
    for await (const chunk of stream) {
    }
  } catch(e) {
    // Doesn't get here
  }
}

two();

// Node dies. There is no point in wrapping this in an async function. 
// We should use promises now and add an error handler.
async function three() {
  try {
    const stream = new ReadableStream();

    stream.on('data', () => {
      // Gets here
      console.log('Data');
    });
    // Node dies with unhandled error
  } catch(e) {
    // Doesn't get here
  }
}

three();