Inconsistent stream events using destroy method

Version: v8.15.0
Platform: Linux 4.20.0-arch1-1-ARCH
Subsystem: stream

As for official Node.js docs, with a custom Writable, the only standard way to know if the stream has finished, is to listen the finish event.

const { Writable } = require('stream')

const stream = new Writable({
  write(chunk, encoding, callback) {
    callback()
  },
})

stream
  .on('close', () => console.log('close'))
  .on('error', () => console.log('error'))
  .on('finish', () => console.log('finish'))

stream.write('test')
stream.end()

The code above works correctly on both node 8 and 10, with the finish event emitted.

const { Writable } = require('stream')

const stream = new Writable({
  write(chunk, encoding, callback) {
    callback()
  },
})

stream
  .on('close', () => console.log('close'))
  .on('error', () => console.log('error'))
  .on('finish', () => console.log('finish'))

stream.destroy(new Error())

// node v8.15.0
// - finish
// - error
//
// node v10.15.0
// - error
// - close

The problem I've noticed is during the usage of the destroy() method, on node 8 the stream will emit first the finish event, then a error event, and no close event.

On node 10, the finish event is not emitted.

I'm not sure if the problem is node 8 or 10, but by reading the docs I suppose the finish event have to be emitted after a possible error.

cc @nodejs/streams

'close' is always emitted both during normal or error shutdown. This behavior has been added in #18438. Also #19836 is relevant. Both of those are semver-major changes, and the behavior in Node 10 simplifies event management and error handling. If you would like to have the same behavior on Node 8, you can use the http://npm.im/readable-stream module.

This sentence is in the docs:

Not all Writable streams will emit the 'close' event.

needs to be updated as all streams will emit 'close' (because of the changes in the above PRs) if the emitClose: true option is passed in. This is true by default.

As for official Node.js docs, with a custom Writable, the only standard way to know if the stream has finished, is to listen the finish event.

That is not true, as the docs report:

The 'finish' event is emitted after the stream.end() method has been called, and all data has been flushed to the underlying system.

It does not mention anything related to the error conditions. I'm not 100% sure why 'finish' is emitted on Node 8 when an 'error' happens, and it's likely a bug (which we should likely not fix, because 8 has been around for so long).

Thank you for the response.

Just for info, I've noticed the same behavior with Readable streams. I've also found a workaround, a setImmediate (nextTick does not work) on end, finish and close event callbacks does the trick.

doc: document that stream.on('close') was changed in Node 10

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Inconsistent stream events using destroy method #25373

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Inconsistent stream events using destroy method #25373

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bnoordhuis commented on Jan 8, 2019

mcollina commented on Jan 9, 2019

greguz commented on Jan 9, 2019

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