Catch and rethrow error from reducer init in combineReducers

Author: ellbee

src/utils/combineReducers.js

@@ -76,7 +76,15 @@ export default function combineReducers(reducers) {
 
   Object.keys(finalReducers).forEach(key => {
     var reducer = finalReducers[key];
-    if (!sanityError && typeof reducer(undefined, { type: ActionTypes.INIT }) === 'undefined') {
+    var initialState;
+
+    try {
+      initialState = reducer(undefined, { type: ActionTypes.INIT });
+    } catch (e) {
+      sanityError = e;
+    }
+
+    if (!sanityError && typeof initialState === 'undefined') {
       sanityError = new Error(
         `Reducer "${key}" returned undefined during initialization. ` +
         `If the state passed to the reducer is undefined, you must ` +

test/utils/combineReducers.spec.js

@@ -84,6 +84,17 @@ describe('Utils', () => {
       );
     });
 
+    it('should catch error thrown in reducer when initializing and re-throw', () => {
+      const reducer = combineReducers({
+        throwingReducer() {
+          throw new Error('Error thrown in reducer');
+        }
+      });
+      expect(() => reducer({})).toThrow(
+        /Error thrown in reducer/
+      );
+    });
+
     it('should allow a symbol to be used as an action type', () => {
       const increment = Symbol('INCREMENT');