child_process: check execFile args is an array

execFile and spawn have same API signature with respect to optional arg
array and optional options object, they should have same behaviour with
respect to argument validation.

PR-URL: https://github.com/joyent/node/pull/8454
Reviewed-by: Trevor Norris <trev.norris@gmail.com>

lib/child_process.js

@@ -591,7 +591,7 @@ exports.exec = function(command /*, options, callback */) {
 
 
 exports.execFile = function(file /* args, options, callback */) {
-  var args, optionArg, callback;
+  var args = [], optionArg, callback;
   var options = {
     encoding: 'utf8',
     timeout: 0,
@@ -601,18 +601,28 @@ exports.execFile = function(file /* args, options, callback */) {
     env: null
   };
 
-  // Parse the parameters.
+  // Parse the optional positional parameters.
+  var pos = 1;
+  if (pos < arguments.length && Array.isArray(arguments[pos])) {
+    args = arguments[pos++];
+  }
+  else if(pos < arguments.length && arguments[pos] == null) {
+    pos++;
+  }
 
-  if (typeof arguments[arguments.length - 1] === 'function') {
-    callback = arguments[arguments.length - 1];
+  if (pos < arguments.length && typeof arguments[pos] === 'object') {
+    options = util._extend(options, arguments[pos++]);
+  }
+  else if(pos < arguments.length && arguments[pos] == null) {
+    pos++;
   }
 
-  if (Array.isArray(arguments[1])) {
-    args = arguments[1];
-    options = util._extend(options, arguments[2]);
-  } else {
-    args = [];
-    options = util._extend(options, arguments[1]);
+  if (pos < arguments.length && typeof arguments[pos] === 'function') {
+    callback = arguments[pos++];
+  }
+
+  if (pos === 1 && arguments.length > 1) {
+    throw new TypeError('Incorrect value of args option');
   }
 
   var child = spawn(file, args, {

test/simple/test-child-process-spawn-typeerror.js

@@ -22,6 +22,7 @@
 var assert = require('assert');
 var child_process = require('child_process');
 var spawn = child_process.spawn;
+var execFile = child_process.execFile;
 var cmd = (process.platform === 'win32') ? 'dir' : 'ls';
 
 
@@ -34,3 +35,13 @@ assert.throws(function() {
 assert.doesNotThrow(function() {
   spawn(cmd, {});
 });
+
+
+// verify that execFile has same argument parsing behaviour as spawn
+assert.throws(function() {
+  execFile(cmd, 'this is not an array');
+}, TypeError);
+
+assert.doesNotThrow(function() {
+  execFile(cmd, {});
+});