missing end event in streams

[AndreasMadsen]

• Version: master (e7ff00d)
• Platform: All
• Subsystem: stream

1e0f331 introduced an issue where the end event isn't emitted.

The following test case can reproduce it:

'use strict'

const stream = require('stream')

class ReadableArray extends stream.Readable {
 constructor(data) {
 super({ objectMode: true })
 this._data = data
 }

 _read (size) {
 if (this._data.length === 0) return this.push(null);
 this.push(this._data.shift());
 }
}

class PassThroughAsWrapper extends stream.Readable {
 constructor (readable) {
 super({ objectMode: true })

 this._readable = readable
 this._readable.once('end', () => this.push(null))
 }

 _read (size) {
 const data = this._readable.read()
 if (data === null) {
 this._readable.once('readable', () => {
 const data = this._readable.read() // this reads null, but somehow the end event is not emitted
 if (data !== null) return this.push(data)
 // end event handler will call .push()
 })
 } else {
 return this.push(data)
 }
 }
}

const inputData = [{}, {}]
const readable = new ReadableArray(inputData)

let endEvent = false
const result = new PassThroughAsWrapper(
 readable.pipe(new stream.PassThrough({ objectMode: true }))
)
result.once('end', function () { endEvent = true; console.log('end event'); })
result.resume()

process.on('exit', function () {
 if (!endEvent) console.log('no end event')
})

The expected result is end event the actual result is no end event.

/cc @mcollina @mafintosh

[mafintosh]

Fixed by #18372