stream: add no-half-open enforcer only if needed

The listener does not do anything if `allowHalfOpen` is enabled. Add it only when `allowHalfOpen` is disabled. PR-URL: #18953 Reviewed-By: Tobias Nießen <[email protected]> Reviewed-By: Ruben Bridgewater <[email protected]> Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: James M Snell <[email protected]>

Author: lpinca

lib/_stream_duplex.js

@@ -58,10 +58,10 @@ function Duplex(options){
 this.writable=false;
 
 this.allowHalfOpen=true;
-if(options&&options.allowHalfOpen===false)
+if(options&&options.allowHalfOpen===false){
 this.allowHalfOpen=false;
-
-this.once('end',onend);
+this.once('end',onend);
+}
 }
 
 Object.defineProperty(Duplex.prototype,'writableHighWaterMark',{
@@ -96,9 +96,8 @@ Object.defineProperty(Duplex.prototype, 'writableLength',{
 
 // the no-half-open enforcer
 functiononend(){
-// if we allow half-open state, or if the writable side ended,
-// then we're ok.
-if(this.allowHalfOpen||this._writableState.ended)
+// If the writable side ended, then we're ok.
+if(this._writableState.ended)
 return;
 
 // no more data can be written.

test/parallel/test-stream-duplex.js

@@ -29,6 +29,8 @@ const stream = new Duplex({objectMode: true });
 assert(Duplex()instanceofDuplex);
 assert(stream._readableState.objectMode);
 assert(stream._writableState.objectMode);
+assert(stream.allowHalfOpen);
+assert.strictEqual(stream.listenerCount('end'),0);
 
 letwritten;
 letread;