child_process: refactor stdioStringToArray function

lib/child_process.js

@@ -37,7 +37,6 @@ const {
   ERR_CHILD_PROCESS_IPC_REQUIRED,
   ERR_CHILD_PROCESS_STDIO_MAXBUFFER,
   ERR_INVALID_ARG_TYPE,
-  ERR_INVALID_OPT_VALUE,
   ERR_OUT_OF_RANGE
 } = require('internal/errors').codes;
 const { clearTimeout, setTimeout } = require('timers');
@@ -46,24 +45,14 @@ const child_process = require('internal/child_process');
 const {
   getValidStdio,
   setupChannel,
-  ChildProcess
+  ChildProcess,
+  stdioStringToArray
 } = child_process;
 
 const MAX_BUFFER = 1024 * 1024;
 
 exports.ChildProcess = ChildProcess;
 
-function stdioStringToArray(option) {
-  switch (option) {
-    case 'ignore':
-    case 'pipe':
-    case 'inherit':
-      return [option, option, option, 'ipc'];
-    default:
-      throw new ERR_INVALID_OPT_VALUE('stdio', option);
-  }
-}
-
 exports.fork = function fork(modulePath /* , args, options */) {
   validateString(modulePath, 'modulePath');
 
@@ -104,12 +93,13 @@ exports.fork = function fork(modulePath /* , args, options */) {
   args = execArgv.concat([modulePath], args);
 
   if (typeof options.stdio === 'string') {
-    options.stdio = stdioStringToArray(options.stdio);
+    options.stdio = stdioStringToArray(options.stdio, 'ipc');
   } else if (!Array.isArray(options.stdio)) {
     // Use a separate fd=3 for the IPC channel. Inherit stdin, stdout,
     // and stderr from the parent if silent isn't set.
-    options.stdio = options.silent ? stdioStringToArray('pipe') :
-      stdioStringToArray('inherit');
+    options.stdio = stdioStringToArray(
+      options.silent ? 'pipe' : 'inherit',
+      'ipc');
   } else if (!options.stdio.includes('ipc')) {
     throw new ERR_CHILD_PROCESS_IPC_REQUIRED('options.stdio');
   }

lib/internal/child_process.js

@@ -214,6 +214,21 @@ const handleConversion = {
   }
 };
 
+function stdioStringToArray(stdio, channel) {
+  const options = [];
+
+  switch (stdio) {
+    case 'ignore':
+    case 'pipe': options.push(stdio, stdio, stdio); break;
+    case 'inherit': options.push(0, 1, 2); break;
+    default:
+      throw new ERR_INVALID_OPT_VALUE('stdio', stdio);
+  }
+
+  if (channel) options.push(channel);
+
+  return options;
+}
 
 function ChildProcess() {
   EventEmitter.call(this);
@@ -892,13 +907,7 @@ function getValidStdio(stdio, sync) {
 
   // Replace shortcut with an array
   if (typeof stdio === 'string') {
-    switch (stdio) {
-      case 'ignore': stdio = ['ignore', 'ignore', 'ignore']; break;
-      case 'pipe': stdio = ['pipe', 'pipe', 'pipe']; break;
-      case 'inherit': stdio = [0, 1, 2]; break;
-      default:
-        throw new ERR_INVALID_OPT_VALUE('stdio', stdio);
-    }
+    stdio = stdioStringToArray(stdio);
   } else if (!Array.isArray(stdio)) {
     throw new ERR_INVALID_OPT_VALUE('stdio', inspect(stdio));
   }
@@ -1042,5 +1051,6 @@ module.exports = {
   ChildProcess,
   setupChannel,
   getValidStdio,
+  stdioStringToArray,
   spawnSync
 };