Fix generator error handling (Fix #89) (#101)

* Fix generator error handling (Fix #89)

* Fix generator error handling (Fix #89)

* Fix generator error handling (Fix #89)

Author: regevbr

lib/environment.js

@@ -31,6 +31,25 @@ function splitArgsFromString(argsString) {
   return result;
 }
 
+/**
+ * Wrap callback so it can't get called twice
+ */
+const callbackWrapper = (generator, done) => {
+  if (!done) {
+    return _.noop();
+  }
+  let callbackHandled = false;
+  const callback = err => {
+    if (!callbackHandled) {
+      callbackHandled = true;
+      done(err);
+    }
+  };
+  // If error was thrown, make sure it is handled and only once
+  generator.on('error', callback);
+  return callback;
+};
+
 /**
  * `Environment` object is responsible of handling the lifecyle and bootstrap
  * of generators in a specific environment (your app).
@@ -453,7 +472,9 @@ class Environment extends EventEmitter {
       return console.log(generator.help());
     }
 
-    return generator.run(done);
+    const _callbackWrapper = callbackWrapper(generator, done);
+
+    return generator.run(_callbackWrapper);
   }
 
   /**

test/environment.js

@@ -177,8 +177,24 @@ describe('Environment', () => {
         exec() {}
       };
 
+      this.PromiseFailingStub = class extends Generator {
+
+        install() {
+          return Promise.reject(new Error('some error'));
+        }
+      };
+
+      this.EventFailingStub = class extends Generator {
+
+        install() {
+          return this.emit('error', new Error('some error'));
+        }
+      };
+
       this.runMethod = sinon.spy(Generator.prototype, 'run');
       this.env.registerStub(this.Stub, 'stub:run');
+      this.env.registerStub(this.PromiseFailingStub, 'promisefailingstub:run');
+      this.env.registerStub(this.EventFailingStub, 'eventfailingstub:run');
     });
 
     afterEach(function () {
@@ -248,6 +264,35 @@ describe('Environment', () => {
       this.env.run('some:unknown:generator');
     });
 
+    it('generator promise error calls callback properly', function (done) {
+      this.env.run('promisefailingstub:run', err => {
+        assert.ok(this.runMethod.calledOnce);
+        assert.ok(err instanceof Error);
+        assert.equal(err.message, 'some error');
+        done();
+      });
+    });
+
+    it('generator error event calls callback properly', function (done) {
+      this.env.run('eventfailingstub:run', err => {
+        assert.ok(this.runMethod.calledOnce);
+        assert.ok(err instanceof Error);
+        assert.equal(err.message, 'some error');
+        done();
+      });
+    });
+
+    it('generator error event emits error event when no callback passed', function (done) {
+      const generator = this.env.run('eventfailingstub:run');
+      assert.equal(generator.listenerCount('error'), 0);
+      generator.on('error', err => {
+        assert.ok(this.runMethod.calledOnce);
+        assert.ok(err instanceof Error);
+        assert.equal(err.message, 'some error');
+        done();
+      });
+    });
+
     it('returns the generator', function () {
       assert.ok(this.env.run('stub:run') instanceof Generator);
     });