Add onUnhandledMesssage handler

Summary: This diff adds the `client.onUnhandledMessage` handler, to be able to handle messages for which we don't know the names upfront. Some existing plugins that only send one kind of message can benefit from this, as can generic plugins, like the createTablePlugin

Reviewed By: passy

Differential Revision: D24949453

fbshipit-source-id: 0fed81e28aee350632c09ee3bb834f306dc8b100

desktop/flipper-plugin/src/__tests__/TestPlugin.tsx

@@ -36,6 +36,7 @@ export function plugin(client: PluginClient<Events, Methods>) {
       persist: 'counter',
     },
   );
+  const unhandledMessages = createState<any[]>([]);
 
   client.onConnect(connectStub);
   client.onDisconnect(disconnectStub);
@@ -47,6 +48,11 @@ export function plugin(client: PluginClient<Events, Methods>) {
       draft.count += delta;
     });
   });
+  client.onUnhandledMessage((event, params) => {
+    unhandledMessages.update((draft) => {
+      draft.push({event, params});
+    });
+  });
 
   function _unused_JustTypeChecks() {
     // @ts-expect-error Argument of type '"bla"' is not assignable
@@ -77,6 +83,7 @@ export function plugin(client: PluginClient<Events, Methods>) {
     disconnectStub,
     getCurrentState,
     state,
+    unhandledMessages,
     appId: client.appId,
     appName: client.appName,
   };

desktop/flipper-plugin/src/__tests__/test-utils.node.tsx

@@ -180,6 +180,15 @@ test('a plugin can receive messages', async () => {
       },
     }
   `);
+
+  expect(instance.unhandledMessages.get().length).toBe(0);
+  sendEvent('unhandled' as any, {hello: 'world'});
+  expect(instance.unhandledMessages.get()).toEqual([
+    {
+      event: 'unhandled',
+      params: {hello: 'world'},
+    },
+  ]);
 });
 
 test('plugins support non-serializable state', async () => {

desktop/flipper-plugin/src/plugin/Plugin.tsx

@@ -63,6 +63,13 @@ export interface PluginClient<
     callback: (params: Events[Event]) => void,
   ): void;
 
+  /**
+   * Subscribe to all messages arriving from the devices not handled by another listener.
+   *
+   * This handler is untyped, and onMessage should be favored over using onUnhandledMessage if the event name is known upfront.
+   */
+  onUnhandledMessage(callback: (event: string, params: any) => void): void;
+
   /**
    * Send a message to the connected client
    */
@@ -156,6 +163,9 @@ export class SandyPluginInstance extends BasePluginInstance {
       onMessage: (event, callback) => {
         this.events.on('event-' + event, callback);
       },
+      onUnhandledMessage: (callback) => {
+        this.events.on('unhandled-event', callback);
+      },
       supportsMethod: async (method) => {
         this.assertConnected();
         return await realClient.supportsMethod(
@@ -212,7 +222,11 @@ export class SandyPluginInstance extends BasePluginInstance {
 
   receiveMessages(messages: Message[]) {
     messages.forEach((message) => {
-      this.events.emit('event-' + message.method, message.params);
+      if (this.events.listenerCount('event-' + message.method) > 0) {
+        this.events.emit('event-' + message.method, message.params);
+      } else {
+        this.events.emit('unhandled-event', message.method, message.params);
+      }
     });
   }