Helpful error when child_process.exec hit maxBuffer

lib/child_process.js

@@ -60,6 +60,8 @@ exports.execFile = function(file /* args, options, callback */) {
   var exited = false;
   var timeoutId;
 
+  var err;
+
   function exithandler(code, signal) {
     if (exited) return;
     exited = true;
@@ -71,7 +73,9 @@ exports.execFile = function(file /* args, options, callback */) {
 
     if (!callback) return;
 
-    if (code === 0 && signal === null) {
+    if (err) {
+      callback(err, stdout, stderr);
+    } else if (code === 0 && signal === null) {
       callback(null, stdout, stderr);
     } else {
       var e = new Error('Command failed: ' + stderr);
@@ -103,6 +107,7 @@ exports.execFile = function(file /* args, options, callback */) {
   child.stdout.addListener('data', function(chunk) {
     stdout += chunk;
     if (stdout.length > options.maxBuffer) {
+      err = new Error('maxBuffer exceeded.');
       kill();
     }
   });
@@ -110,6 +115,7 @@ exports.execFile = function(file /* args, options, callback */) {
   child.stderr.addListener('data', function(chunk) {
     stderr += chunk;
     if (stderr.length > options.maxBuffer) {
+      err = new Error('maxBuffer exceeded.');
       kill();
     }
   });

test/simple/test-exec-max-buffer.js

@@ -0,0 +1,10 @@
+var common = require('../common');
+var exec = require('child_process').exec;
+var assert = require('assert');
+
+var cmd = 'echo "hello world"';
+
+exec(cmd, { maxBuffer: 5 }, function(err, stdout, stderr) {
+  assert.ok(err);
+  assert.ok(/maxBuffer/.test(err.message));
+});