Merge pull request #37 from marcins/36-fix-interop-with-devtools

change method for detemrining whether state is already wrapped in reducer

Fixes #36

__tests__/index-tests.js

@@ -8,6 +8,7 @@ import {
   ensureState
 } from '../src/index';
 import {createStore, combineReducers} from 'redux';
+import instrument from 'redux-devtools-instrument';
 
 // while there isn't an Immutable dependency in the library anymore we want to verify backwards
 // compat with immutable wrapped reducers
@@ -435,3 +436,18 @@ test('with redux and initialState without preloadState', t => {
     t.fail(error.message)
   }
 });
+
+test('works with preloadState and redux-devtools-instrumentation', t => {
+  const enhancedReducer = combineReducers({
+    counter: optimistic(counterReducer)
+  });
+  try {
+    const store = createStore(enhancedReducer, {
+      counter: 1
+    }, instrument((state, action) => state));
+    store.dispatch({type: 'INC'});
+    t.is(ensureState(store.getState().counter), 2);
+  } catch (error) {
+    t.fail(error.message)
+  }
+});

package.json

@@ -40,6 +40,7 @@
     "immutable": "^3.8.1",
     "nyc": "^6.6.1",
     "redux": "^3.6.0",
+    "redux-devtools-instrument": "^1.8.2",
     "rimraf": "^2.5.3"
   },
   "nyc": {

src/index.js

@@ -4,12 +4,12 @@ export const BEGIN = '@@optimist/BEGIN';
 export const COMMIT = '@@optimist/COMMIT';
 export const REVERT = '@@optimist/REVERT';
 
-export const ensureState = state => {
-  if (state && Array.isArray(state.history)) {
-    return state.current;
-  }
-  return state;
-};
+const isOptimistState = state => state && Object.keys(state).length === 3
+  && state.hasOwnProperty('beforeState')
+  && state.hasOwnProperty('history')
+  && state.hasOwnProperty('current');
+
+export const ensureState = state => isOptimistState(state) ? state.current : state;
 
 const createState = state => ({
   beforeState: undefined,
@@ -98,7 +98,7 @@ export const optimistic = (reducer, rawConfig = {}) => {
   }, rawConfig);
 
   return (state, action) => {
-    if (state === undefined || action.type === '@@redux/INIT') {
+    if (state === undefined || !isOptimistState(state)) {
       state = createState(reducer(ensureState(state), {}));
     }
     const historySize = state.history.length;