Add '--run-in-band' option to run in the current process

bin/jscodeshift.sh

@@ -58,6 +58,12 @@ var opts = require('nomnom')
     extensions: {
       default: 'js',
       help: 'File extensions the transform file should be applied to'
+    },
+    runInBand: {
+      flag: true,
+      default: false,
+      full: 'run-in-band',
+      help: 'Run serially in the current process'
     }
   })
   .parse();

src/Runner.js

@@ -109,22 +109,24 @@ function run(transformFile, paths, options) {
       }
 
       console.log('Processing %d files...', files.length);
-      console.log(
-        'Spawning %d workers with %d files each...',
-        fileChunks.length,
-        fileChunks[0].length
-      );
+      if (!options.runInBand) {
+        console.log(
+          'Spawning %d workers with %d files each...',
+          fileChunks.length,
+          fileChunks[0].length
+        );
+      }
       if (options.dry) {
         console.log(
           clc.green('Running in dry mode, no files will be written!')
         );
       }
 
       return fileChunks.map(files => {
-        const child = child_process.fork(
-          require.resolve('./Worker'),
-          [transformFile, options.babel ? 'babel' : 'no-babel']
-        );
+        const args = [transformFile, options.babel ? 'babel' : 'no-babel'];
+        const child = options.runInBand ?
+          require('./Worker')(args) :
+          child_process.fork(require.resolve('./Worker'), args);
         child.send({files, options});
         child.on('message', message => {
           switch (message.action) {
@@ -146,7 +148,7 @@ function run(transformFile, paths, options) {
     .then(pendingWorkers =>
       Promise.all(pendingWorkers).then(() => {
         const endTime = process.hrtime(startTime);
-        console.log('All workers done.');
+        console.log('All done.');
         showFileStats(fileCounters);
         showStats(statsCounter);
         console.log(

src/Worker.js

@@ -10,26 +10,51 @@
 
 'use strict';
 
-if (process.argv[3] === 'babel') {
-  require('babel-core/register')();
-}
+const EventEmitter = require('events').EventEmitter;
+
+const async = require('async');
+const fs = require('fs');
 
-var async = require('async');
-var fs = require('fs');
+const jscodeshift = require('./core');
 
-var jscodeshift = require('./core');
-var transform = require(process.argv[2]);
+let emitter;
+let finish;
+let notify;
+let transform;
+
+if (module.parent) {
+  emitter = new EventEmitter();
+  emitter.send = (data) => { run(data); };
+  finish = () => { emitter.emit('disconnect'); };
+  notify = (data) => { emitter.emit('message', data); };
+  module.exports = (args) => {
+    setup(args[0], args[1]);
+    return emitter;
+  };
+} else {
+  finish = () => { process.disconnect(); };
+  notify = (data) => { process.send(data); };
+  process.on('message', (data) => { run(data); });
+  setup(process.argv[2], process.argv[3]);
+}
+
+function setup(tr, babel) {
+  if (babel === 'babel') {
+    require('babel-core/register')();
+  }
+  transform = require(tr);
+}
 
 function updateStatus(status, file, msg) {
   msg = msg  ?  file + ' ' + msg : file;
-  process.send({action: 'status', status: status, msg: msg});
+  notify({action: 'status', status: status, msg: msg});
 }
 
 function empty() {}
 
 function stats(name, quantity) {
   quantity = typeof quantity !== 'number' ? 1 : quantity;
-  process.send({action: 'update', name: name, quantity: quantity});
+  notify({action: 'update', name: name, quantity: quantity});
 }
 
 function trimStackTrace(trace) {
@@ -45,7 +70,7 @@ function trimStackTrace(trace) {
   return result.join('\n');
 }
 
-process.on('message', function(data) {
+function run(data) {
   var files = data.files;
   var options = data.options;
   async.each(
@@ -105,7 +130,7 @@ process.on('message', function(data) {
       if (err) {
         updateStatus('error', '', 'This should never be shown!');
       }
-      process.disconnect();
+      finish();
     }
   );
-});
+}