Add an explicit private action type for replacing reducers

Author: timdorr

src/combineReducers.js

@@ -44,6 +44,8 @@ function getUnexpectedStateShapeWarningMessage(inputState, reducers, action, une
     unexpectedKeyCache[key] = true
   })
 
+  if (action && action.type == ActionTypes.REPLACE) return
+
   if (unexpectedKeys.length > 0) {
     return (
       `Unexpected ${unexpectedKeys.length > 1 ? 'keys' : 'key'} ` +

src/createStore.js

@@ -213,7 +213,7 @@ export default function createStore(reducer, preloadedState, enhancer) {
     }
 
     currentReducer = nextReducer
-    dispatch({ type: ActionTypes.INIT })
+    dispatch({ type: ActionTypes.REPLACE })
   }
 
   /**

src/utils/actionTypes.js

@@ -5,7 +5,8 @@
  * Do not reference these action types directly in your code.
  */
 var ActionTypes = {
-  INIT: '@@redux/INIT'
+  INIT: '@@redux/INIT',
+  REPLACE: '@@redux/REPLACE'
 }
 
 export default ActionTypes

test/createStore.spec.js

@@ -1,12 +1,12 @@
 import { createStore, combineReducers } from '../src/index'
-import { 
-  addTodo, 
-  dispatchInMiddle, 
+import {
+  addTodo,
+  dispatchInMiddle,
   getStateInMiddle,
   subscribeInMiddle,
   unsubscribeInMiddle,
-  throwError, 
-  unknownAction 
+  throwError,
+  unknownAction
 } from './helpers/actionCreators'
 import * as reducers from './helpers/reducers'
 import * as Rx from 'rxjs'
@@ -767,4 +767,30 @@ describe('createStore', () => {
       expect(results).toEqual([ { foo: 0, bar: 0, fromRx: true }, { foo: 1, bar: 0, fromRx: true } ])
     })
   })
+
+  it('does not log an error if parts of the current state will be ignored by a nextReducer using combineReducers', () => {
+    const originalConsoleError = console.error
+    console.error = jest.fn()
+
+    const store = createStore(
+      combineReducers({
+        x: (s=0, a) => s,
+        y: combineReducers({
+          z: (s=0, a) => s,
+          w: (s=0, a) => s,
+        }),
+      })
+    )
+
+    store.replaceReducer(
+      combineReducers({
+        y: combineReducers({
+          z: (s=0, a) => s,
+        }),
+      })
+    )
+
+    expect(console.error.mock.calls.length).toBe(0)
+    console.error = originalConsoleError
+  })
 })