Add method to channel that ignores event from self

lib/channels/README.md

@@ -15,6 +15,7 @@ Channels are used with Storybook implementations to send/receive events between
 ```js
 class Channel {
   addListener(type, listener) {}
+  addPeerListener(type, listener) {} // ignore events from itself
   emit(type, ...args) {}
   eventNames() {}
   listenerCount(type) {}

lib/channels/src/index.js

@@ -12,6 +12,12 @@ export default class Channel {
     this.on(type, listener);
   }
 
+  addPeerListener(type, listener) {
+    const peerListener = listener;
+    peerListener.isPeer = from => from === this._sender;
+    this.on(type, peerListener);
+  }
+
   emit(type, ...args) {
     const event = { type, args, from: this._sender };
     this._transport.send(event);
@@ -75,7 +81,7 @@ export default class Channel {
   _handleEvent(event) {
     const listeners = this._listeners[event.type];
     if (listeners) {
-      listeners.forEach(fn => fn(...event.args));
+      listeners.forEach(fn => !(fn.isPeer && fn.isPeer(event.from)) && fn(...event.args));
     }
   }
 

lib/channels/src/index.test.js

@@ -113,6 +113,25 @@ describe('Channel', () => {
     });
   });
 
+
+  describe('method:addPeerListener', () => {
+    it('should add event listeners', () => {
+      channel.addPeerListener('type-1', () => {});
+      channel.addPeerListener('type-2', () => {});
+      channel.addPeerListener('type-2', () => {});
+      expect(channel._listeners['type-1'].length).toEqual(1);
+      expect(channel._listeners['type-2'].length).toEqual(2);
+    });
+
+    it('should call event listeners on event', () => {
+      const received = [];
+      channel.addPeerListener('type-1', n => received.push(n));
+      channel._handleEvent({ type: 'type-1', args: [11] });
+      channel._handleEvent({ type: 'type-1', args: [12] });
+      expect(received).toEqual([11, 12]);
+    });
+  });
+
   describe('method:prependListener', () => {
     it('should add event listeners', () => {
       channel.prependListener('type-1', 11);
@@ -184,5 +203,13 @@ describe('Channel', () => {
       channel._handleEvent({ type: 'type-1', args: [12], from: channel._sender });
       expect(received).toEqual([11, 12]);
     });
+
+    it('should ignore if event handled by addPeerListener', () => {
+      const received = [];
+      channel.addPeerListener('type-1', n => received.push(n));
+      channel._handleEvent({ type: 'type-1', args: [11], from: channel._sender });
+      channel._handleEvent({ type: 'type-1', args: [12], from: '_'});
+      expect(received).toEqual([12]);
+    });
   });
 });