Add returnNewGenerator option to composeWith (#1157)

lib/index.js

@@ -657,8 +657,9 @@ class Generator extends EventEmitter {
   /**
    * Compose this generator with another one.
    * @param  {String|Object|Array} generator  The path to the generator module or an object (see examples)
-   * @param  {Object} options    The options passed to the Generator
-   * @return {this}    This generator
+   * @param  {Object}  [options]   The options passed to the Generator
+   * @param  {boolean} [returnNewGenerator] Returns the created generator instead of returning this.
+   * @return {this|Object}    This generator or the composed generator when returnNewGenerator=true
    *
    * @example <caption>Using a peerDependency generator</caption>
    * this.composeWith('bootstrap', { sass: true });
@@ -669,7 +670,11 @@ class Generator extends EventEmitter {
    * @example <caption>Passing a Generator class</caption>
    * this.composeWith({ Generator: MyGenerator, path: '../generator-bootstrap/app/main.js' }, { sass: true });
    */
-  composeWith(generator, options) {
+  composeWith(generator, options, returnNewGenerator = false) {
+    if (typeof options === 'boolean') {
+      returnNewGenerator = options;
+    }
+
     let instantiatedGenerator;
 
     if (Array.isArray(generator)) {
@@ -763,6 +768,10 @@ class Generator extends EventEmitter {
       this._composedWith.push(instantiatedGenerator);
     }
 
+    if (returnNewGenerator) {
+      return instantiatedGenerator;
+    }
+
     return this;
   }
 

test/base.js

@@ -736,6 +736,10 @@ describe('Base', () => {
       this.env.registerStub(this.GenCompose, 'composed:gen');
     });
 
+    it('returns the composed generator when pass true', function() {
+      assert(this.dummy.composeWith('composed:gen', true) instanceof this.GenCompose);
+    });
+
     it('runs the composed generators', function(done) {
       this.dummy.composeWith('composed:gen');