http: don't double-fire the req error event

req.socket._hadError should be set before emitting the error event.
PR-URL: #14659
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

Author: fengmk2

lib/_http_client.js

@@ -373,8 +373,8 @@ function socketCloseListener() {
 // This socket error fired before we started to
 // receive a response. The error needs to
 // fire on the request.
-req.emit('error',createHangUpError());
 req.socket._hadError=true;
+req.emit('error',createHangUpError());
 }
 
 // Too bad. That output wasn't getting written.
@@ -397,10 +397,10 @@ function socketErrorListener(err) {
 debug('SOCKET ERROR:',err.message,err.stack);
 
 if(req){
-req.emit('error',err);
 // For Safety. Some additional errors might fire later on
 // and we need to make sure we don't double-fire the error event.
 req.socket._hadError=true;
+req.emit('error',err);
 }
 
 // Handle any pending data
@@ -433,8 +433,8 @@ function socketOnEnd() {
 if(!req.res&&!req.socket._hadError){
 // If we don't have a response then we know that the socket
 // ended prematurely and we need to emit an error on the request.
-req.emit('error',createHangUpError());
 req.socket._hadError=true;
+req.emit('error',createHangUpError());
 }
 if(parser){
 parser.finish();
@@ -455,8 +455,8 @@ function socketOnData(d) {
 debug('parse error',ret);
 freeParser(parser,req,socket);
 socket.destroy();
-req.emit('error',ret);
 req.socket._hadError=true;
+req.emit('error',ret);
 }elseif(parser.incoming&&parser.incoming.upgrade){
 // Upgrade or CONNECT
 varbytesParsed=ret;

test/parallel/test-http-client-req-error-dont-double-fire.js

@@ -0,0 +1,16 @@
+'use strict';
+constassert=require('assert');
+consthttp=require('http');
+constcommon=require('../common');
+
+// not exists host
+consthost='*'.repeat(256);
+constreq=http.get({ host });
+consterr=newError('mock unexpected code error');
+req.on('error',common.mustCall(()=>{
+throwerr;
+}));
+
+process.on('uncaughtException',common.mustCall((e)=>{
+assert.strictEqual(e,err);
+}));