add callback function support for generator scheduling (#521)

---------

Co-authored-by: Marcelo Shima <marceloshima@gmail.com>

src/environment-base.ts

@@ -422,10 +422,12 @@ export default class EnvironmentBase extends EventEmitter implements BaseEnviron
   ): Promise<G>;
   async composeWith<G extends BaseGenerator = BaseGenerator>(generator: string | GetGeneratorConstructor<G>, ...args: any[]): Promise<G> {
     const options = getComposeOptions(...args) as ComposeOptions<G>;
-    const { schedule = true, ...instantiateOptions } = options;
+    const { schedule: passedSchedule = true, ...instantiateOptions } = options;
 
     const generatorInstance = await this.create(generator, instantiateOptions);
-    return this.queueGenerator(generatorInstance, { schedule });
+    // Convert to function to keep type compatibility with old @yeoman/types where schedule is boolean only
+    const schedule: (gen: G) => boolean = typeof passedSchedule === 'function' ? passedSchedule : () => passedSchedule;
+    return this.queueGenerator(generatorInstance, { schedule: schedule(generatorInstance) });
   }
 
   /**

test/environment.js

@@ -272,6 +272,18 @@ for (const generatorVersion of allVersions) {
           }
         });
       });
+      describe('passing function schedule parameter', () => {
+        it('returning false should not schedule generator', async function () {
+          this.env.queueTask = sinon.spy();
+          await this.env.composeWith('stub', { generatorArgs: [], schedule: () => false });
+          if (isGreaterThan6(generatorVersion)) {
+            assert(this.env.queueTask.calledOnce);
+            assert(this.env.queueTask.getCall(0).firstArg !== 'environment:run');
+          } else {
+            assert(this.env.queueTask.notCalled);
+          }
+        });
+      });
 
       it('should emit a compose event', function (done) {
         this.env.once('compose', (namespace, generator) => {