feat(ui-store): onDisconnect on ui-store

decls/vars.js

@@ -14,6 +14,9 @@ declare var chrome: {
                 sender: ?string,
                 cb: (res: any) => void
             ) => ?boolean) => void
+        },
+        onDisconnect: {
+            addListener: (handler: () => ?boolean) => void
         }
     }
 };

src/ui-store.js

@@ -8,6 +8,7 @@ import {
 
 let listeners = [];
 let state;
+let onDisconnect;
 
 function handleMessage(msg: Object): void {
     if (msg.type === UPDATE_STATE) {
@@ -17,6 +18,12 @@ function handleMessage(msg: Object): void {
     }
 }
 
+function handleDisconnect(): void {
+    if (onDisconnect) {
+        onDisconnect();
+    }
+}
+
 function subscribe(listener: EmptyFunc): EmptyFunc {
     listeners.push(listener);
 
@@ -38,13 +45,23 @@ function getState(): Object {
     return state;
 }
 
-export default function (): Promise<Store> {
+export default function (options?: {
+    onDisconnect?: EmptyFunc,
+} = {}): Promise<Store> {
+    if (options.hasOwnProperty('onDisconnect') && typeof options.onDisconnect !== 'function') {
+        return Promise.reject(new Error('Expected the "onDisconnect" to be a function.'));
+    }
+
+    onDisconnect = options.onDisconnect;
+
     // connect to "background" store
     const connection = chrome.runtime.connect({name: CONNECTION_NAME});
 
     // listen for changes in the "background" store
     connection.onMessage.addListener(handleMessage);
 
+    connection.onDisconnect.addListener(handleDisconnect);
+
     // return promise to allow getting current state of "background" store
     return new Promise(resolve => {
         chrome.runtime.sendMessage({type: UPDATE_STATE}, res => {

tests/ui-store.js

@@ -9,6 +9,9 @@ async function createStore(state) {
     const connection = {
         onMessage: {
             addListener: jest.fn()
+        },
+        onDisconnect: {
+            addListener: jest.fn()
         }
     };