child_process: fix exec set stdout.setEncoding

cp.exec decide to use `_stdout`(_stdout is string) or
`Buffer.concat(_stdout)`(_stdout is buffer array) by options.encoding.
but std(out|err) encoding can be changed. If encoding is changed to
not null, `_stdout` will become string, and `Buffer.concat(_stdout)`
will throw TypeError. This patch will fix it, use
options.encoding and `std(out|err)._readableState.encoding`.
PR-URL: #18976Fixes: #18969
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

Author: killagu

lib/_stream_readable.js

@@ -324,7 +324,8 @@ Readable.prototype.setEncoding = function(enc) {
 if(!StringDecoder)
 StringDecoder=require('string_decoder').StringDecoder;
 this._readableState.decoder=newStringDecoder(enc);
-this._readableState.encoding=enc;
+// if setEncoding(null), decoder.encoding equals utf8
+this._readableState.encoding=this._readableState.decoder.encoding;
 returnthis;
 };
 

lib/child_process.js

@@ -226,15 +226,11 @@ exports.execFile = function execFile(file /* , args, options, callback */) {
 });
 
 varencoding;
-var_stdout;
-var_stderr;
+var_stdout=[];
+var_stderr=[];
 if(options.encoding!=='buffer'&&Buffer.isEncoding(options.encoding)){
 encoding=options.encoding;
-_stdout='';
-_stderr='';
 }else{
-_stdout=[];
-_stderr=[];
 encoding=null;
 }
 varstdoutLen=0;
@@ -261,11 +257,24 @@ exports.execFile = function execFile(file /* , args, options, callback */) {
 // merge chunks
 varstdout;
 varstderr;
-if(encoding){
-stdout=_stdout;
-stderr=_stderr;
+if(encoding||
+(
+child.stdout&&
+child.stdout._readableState&&
+child.stdout._readableState.encoding
+)){
+stdout=_stdout.join('');
 }else{
 stdout=Buffer.concat(_stdout);
+}
+if(encoding||
+(
+child.stderr&&
+child.stderr._readableState&&
+child.stderr._readableState.encoding
+)){
+stderr=_stderr.join('');
+}else{
 stderr=Buffer.concat(_stderr);
 }
 
@@ -329,13 +338,12 @@ exports.execFile = function execFile(file /* , args, options, callback */) {
 child.stdout.setEncoding(encoding);
 
 child.stdout.on('data',functiononChildStdout(chunk){
+varencoding=child.stdout._readableState.encoding;
 stdoutLen+=encoding ? Buffer.byteLength(chunk,encoding) : chunk.length;
 
 if(stdoutLen>options.maxBuffer){
 ex=newERR_CHILD_PROCESS_STDIO_MAXBUFFER('stdout');
 kill();
-}elseif(encoding){
-_stdout+=chunk;
 }else{
 _stdout.push(chunk);
 }
@@ -347,13 +355,12 @@ exports.execFile = function execFile(file /* , args, options, callback */) {
 child.stderr.setEncoding(encoding);
 
 child.stderr.on('data',functiononChildStderr(chunk){
+varencoding=child.stderr._readableState.encoding;
 stderrLen+=encoding ? Buffer.byteLength(chunk,encoding) : chunk.length;
 
 if(stderrLen>options.maxBuffer){
 ex=newERR_CHILD_PROCESS_STDIO_MAXBUFFER('stderr');
 kill();
-}elseif(encoding){
-_stderr+=chunk;
 }else{
 _stderr.push(chunk);
 }

test/parallel/test-child-process-exec-maxBuffer.js

@@ -41,3 +41,25 @@ const unicode = '中文测试'; // length = 4, byte length = 12
 
 cp.exec(cmd,{maxBuffer: 10},checkFactory('stderr'));
 }
+
+{
+constcmd=`"${process.execPath}" -e "console.log('${unicode}');"`;
+
+constchild=cp.exec(
+cmd,
+{encoding: null,maxBuffer: 10},
+checkFactory('stdout'));
+
+child.stdout.setEncoding('utf-8');
+}
+
+{
+constcmd=`"${process.execPath}" -e "console.error('${unicode}');"`;
+
+constchild=cp.exec(
+cmd,
+{encoding: null,maxBuffer: 10},
+checkFactory('stderr'));
+
+child.stderr.setEncoding('utf-8');
+}

test/parallel/test-child-process-exec-std-encoding.js

@@ -0,0 +1,23 @@
+'use strict';
+constcommon=require('../common');
+constassert=require('assert');
+constcp=require('child_process');
+conststdoutData='foo';
+conststderrData='bar';
+constexpectedStdout=`${stdoutData}\n`;
+constexpectedStderr=`${stderrData}\n`;
+
+if(process.argv[2]==='child'){
+// The following console calls are part of the test.
+console.log(stdoutData);
+console.error(stderrData);
+}else{
+constcmd=`"${process.execPath}" "${__filename}" child`;
+constchild=cp.exec(cmd,common.mustCall((err,stdout,stderr)=>{
+assert.ifError(err);
+assert.strictEqual(stdout,expectedStdout);
+assert.strictEqual(stderr,expectedStderr);
+}));
+child.stdout.setEncoding('utf-8');
+child.stderr.setEncoding('utf-8');
+}

test/parallel/test-stream-readable-setEncoding-null.js

@@ -0,0 +1,15 @@
+'use strict';
+
+require('../common');
+constassert=require('assert');
+const{ Readable }=require('stream');
+
+
+{
+constreadable=newReadable({encoding: 'hex'});
+assert.strictEqual(readable._readableState.encoding,'hex');
+
+readable.setEncoding(null);
+
+assert.strictEqual(readable._readableState.encoding,'utf8');
+}