Fix redux support for observables

reduxjs/redux-devtools#275

package.json

@@ -47,10 +47,13 @@
     "expect": "^1.6.0",
     "isparta": "^3.0.3",
     "mocha": "^2.2.5",
-    "redux": "^3.0.0",
-    "rimraf": "^2.3.4"
+    "redux": "^3.5.2",
+    "rimraf": "^2.3.4",
+    "rxjs": "^5.0.0-beta.6",
+    "webpack": "^1.11.0"
   },
   "dependencies": {
-    "lodash": "^4.2.0"
+    "lodash": "^4.2.0",
+    "symbol-observable": "^0.2.4"
   }
 }

src/instrument.js

@@ -1,6 +1,7 @@
 import difference from 'lodash/difference';
 import union from 'lodash/union';
 import isPlainObject from 'lodash/isPlainObject';
+import $$observable from 'symbol-observable';
 
 export const ActionTypes = {
   PERFORM_ACTION: 'PERFORM_ACTION',
@@ -392,6 +393,14 @@ export function unliftState(liftedState) {
 export function unliftStore(liftedStore, liftReducer) {
   let lastDefinedState;
 
+  function getState() {
+    const state = unliftState(liftedStore.getState());
+    if (state !== undefined) {
+      lastDefinedState = state;
+    }
+    return lastDefinedState;
+  }
+
   return {
     ...liftedStore,
 
@@ -402,16 +411,31 @@ export function unliftStore(liftedStore, liftReducer) {
       return action;
     },
 
-    getState() {
-      const state = unliftState(liftedStore.getState());
-      if (state !== undefined) {
-        lastDefinedState = state;
-      }
-      return lastDefinedState;
-    },
+    getState,
 
     replaceReducer(nextReducer) {
       liftedStore.replaceReducer(liftReducer(nextReducer));
+    },
+
+    [$$observable]() {
+      return {
+        ...liftedStore[$$observable](),
+        subscribe(observer) {
+          if (typeof observer !== 'object') {
+            throw new TypeError('Expected the observer to be an object.');
+          }
+
+          function observeState() {
+            if (observer.next) {
+              observer.next(getState());
+            }
+          }
+
+          observeState();
+          const unsubscribe = liftedStore.subscribe(observeState);
+          return { unsubscribe };
+        }
+      };
     }
   };
 }

test/instrument.spec.js

@@ -1,6 +1,9 @@
 import expect, { spyOn } from 'expect';
 import { createStore, compose } from 'redux';
 import instrument, { ActionCreators } from '../src/instrument';
+import { Observable } from 'rxjs';
+
+import 'rxjs/add/observable/from';
 
 function counter(state = 0, action) {
   switch (action.type) {
@@ -53,6 +56,21 @@ describe('instrument', () => {
     expect(store.getState()).toBe(2);
   });
 
+  it('should provide observable', () => {
+    let lastValue;
+    let calls = 0;
+
+    Observable.from(store)
+        .subscribe(state => {
+          lastValue = state;
+          calls++;
+        });
+
+    expect(lastValue).toBe(0);
+    store.dispatch({ type: 'INCREMENT' });
+    expect(lastValue).toBe(1);
+  });
+
   it('should rollback state to the last committed state', () => {
     store.dispatch({ type: 'INCREMENT' });
     store.dispatch({ type: 'INCREMENT' });