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

Fixes: #24281
PR-URL: #24366
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

Author: mcollina

lib/_stream_readable.js

@@ -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;
@@ -858,10 +859,16 @@ Readable.prototype.removeAllListeners = function(ev) {
 };
 
 functionupdateReadableListening(self){
-self._readableState.readableListening=self.listenerCount('readable')>0;
+conststate=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
+}elseif(self.listenerCount('data')>0){
 self.resume();
 }
 }
@@ -883,6 +890,7 @@ Readable.prototype.resume = function() {
 state.flowing=!state.readableListening;
 resume(this,state);
 }
+state.paused=false;
 returnthis;
 };
 
@@ -913,6 +921,7 @@ Readable.prototype.pause = function() {
 this._readableState.flowing=false;
 this.emit('pause');
 }
+this._readableState.paused=true;
 returnthis;
 };
 

test/parallel/test-stream-readable-readable-then-resume.js

@@ -0,0 +1,29 @@
+'use strict';
+
+constcommon=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(newReadable({
+objectMode: true,
+highWaterMark: 1,
+read(){
+if(!this.first){
+this.push('hello');
+this.first=true;
+return;
+}
+
+this.push(null);
+}
+}));
+
+functioncheck(s){
+constreadableListener=common.mustNotCall();
+s.on('readable',readableListener);
+s.on('end',common.mustCall());
+s.removeListener('readable',readableListener);
+s.resume();
+}