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stream: correctly pause and resume after once('readable')
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Fixes: #24281

PR-URL: #24366
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Franziska Hinkelmann <[email protected]>
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mcollina authored and codebytere committed Jan 29, 2019
1 parent f0602f8 commit fa60eb8
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Showing 2 changed files with 41 additions and 3 deletions.
15 changes: 12 additions & 3 deletions lib/_stream_readable.js
Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,7 @@ function ReadableState(options, stream, isDuplex) {
this.emittedReadable = false;
this.readableListening = false;
this.resumeScheduled = false;
this.paused = true;

// Should close be emitted on destroy. Defaults to true.
this.emitClose = options.emitClose !== false;
Expand Down Expand Up @@ -858,10 +859,16 @@ Readable.prototype.removeAllListeners = function(ev) {
};

function updateReadableListening(self) {
self._readableState.readableListening = self.listenerCount('readable') > 0;
const state = self._readableState;
state.readableListening = self.listenerCount('readable') > 0;

// crude way to check if we should resume
if (self.listenerCount('data') > 0) {
if (state.resumeScheduled && !state.paused) {
// flowing needs to be set to true now, otherwise
// the upcoming resume will not flow.
state.flowing = true;

// crude way to check if we should resume
} else if (self.listenerCount('data') > 0) {
self.resume();
}
}
Expand All @@ -883,6 +890,7 @@ Readable.prototype.resume = function() {
state.flowing = !state.readableListening;
resume(this, state);
}
state.paused = false;
return this;
};

Expand Down Expand Up @@ -913,6 +921,7 @@ Readable.prototype.pause = function() {
this._readableState.flowing = false;
this.emit('pause');
}
this._readableState.paused = true;
return this;
};

Expand Down
29 changes: 29 additions & 0 deletions test/parallel/test-stream-readable-readable-then-resume.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
'use strict';

const common = require('../common');
const { Readable } = require('stream');

// This test verifies that a stream could be resumed after
// removing the readable event in the same tick

check(new Readable({
objectMode: true,
highWaterMark: 1,
read() {
if (!this.first) {
this.push('hello');
this.first = true;
return;
}

this.push(null);
}
}));

function check(s) {
const readableListener = common.mustNotCall();
s.on('readable', readableListener);
s.on('end', common.mustCall());
s.removeListener('readable', readableListener);
s.resume();
}

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