child_process: preserve argument type

A previous fix for a `maxBuffer` bug resulted in a change to the
argument type for the `data` event on `child.stdin` and `child.stdout`
when using `child_process.exec()`.

This fixes the `maxBuffer` bug in a way that does not have that side
effect.

PR-URL: #7391
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Jackson Tian <shyvo1987@gmail.com>
Fixes: #7342
Refs: #1901

lib/child_process.js

@@ -190,12 +190,12 @@ exports.execFile = function(file /*, args, options, callback*/) {
     // merge chunks
     var stdout;
     var stderr;
-    if (!encoding) {
-      stdout = Buffer.concat(_stdout);
-      stderr = Buffer.concat(_stderr);
-    } else {
+    if (encoding) {
       stdout = _stdout;
       stderr = _stderr;
+    } else {
+      stdout = Buffer.concat(_stdout);
+      stderr = Buffer.concat(_stderr);
     }
 
     if (ex) {
@@ -260,16 +260,16 @@ exports.execFile = function(file /*, args, options, callback*/) {
       child.stdout.setEncoding(encoding);
 
     child.stdout.addListener('data', function(chunk) {
-      stdoutLen += chunk.length;
+      stdoutLen += encoding ? Buffer.byteLength(chunk, encoding) : chunk.length;
 
       if (stdoutLen > options.maxBuffer) {
         ex = new Error('stdout maxBuffer exceeded');
         kill();
       } else {
-        if (!encoding)
-          _stdout.push(chunk);
-        else
+        if (encoding)
           _stdout += chunk;
+        else
+          _stdout.push(chunk);
       }
     });
   }
@@ -279,16 +279,16 @@ exports.execFile = function(file /*, args, options, callback*/) {
       child.stderr.setEncoding(encoding);
 
     child.stderr.addListener('data', function(chunk) {
-      stderrLen += chunk.length;
+      stderrLen += encoding ? Buffer.byteLength(chunk, encoding) : chunk.length;
 
       if (stderrLen > options.maxBuffer) {
         ex = new Error('stderr maxBuffer exceeded');
         kill();
       } else {
-        if (!encoding)
-          _stderr.push(chunk);
-        else
+        if (encoding)
           _stderr += chunk;
+        else
+          _stderr.push(chunk);
       }
     });
   }

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

@@ -0,0 +1,31 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cp = require('child_process');
+
+function checkFactory(streamName) {
+  return common.mustCall((err) => {
+    const message = `${streamName} maxBuffer exceeded`;
+    assert.strictEqual(err.message, message);
+  });
+}
+
+{
+  const cmd = 'echo "hello world"';
+
+  cp.exec(cmd, { maxBuffer: 5 }, checkFactory('stdout'));
+}
+
+const unicode = '中文测试'; // length = 4, byte length = 12
+
+{
+  const cmd = `"${process.execPath}" -e "console.log('${unicode}');"`;
+
+  cp.exec(cmd, {maxBuffer: 10}, checkFactory('stdout'));
+}
+
+{
+  const cmd = `"${process.execPath}" -e "console.('${unicode}');"`;
+
+  cp.exec(cmd, {maxBuffer: 10}, checkFactory('stderr'));
+}

test/parallel/test-child-process-exec-stdout-data-string.js → test/parallel/test-child-process-exec-stdout-stderr-data-string.js

@@ -4,13 +4,20 @@ const common = require('../common');
 const assert = require('assert');
 const exec = require('child_process').exec;
 
-const expectedCalls = 2;
-
-const cb = common.mustCall((data) => {
-  assert.strictEqual(typeof data, 'string');
-}, expectedCalls);
+var stdoutCalls = 0;
+var stderrCalls = 0;
 
 const command = common.isWindows ? 'dir' : 'ls';
-exec(command).stdout.on('data', cb);
+exec(command).stdout.on('data', (data) => {
+  stdoutCalls += 1;
+});
+
+exec('fhqwhgads').stderr.on('data', (data) => {
+  assert.strictEqual(typeof data, 'string');
+  stderrCalls += 1;
+});
 
-exec('fhqwhgads').stderr.on('data', cb);
+process.on('exit', () => {
+  assert(stdoutCalls > 0);
+  assert(stderrCalls > 0);
+});