Port error message updates from master

errors.json

@@ -1,18 +1,19 @@
 {
-  "0": "It looks like you are passing several store enhancers to createStore(). This is not supported. Instead, compose them together to a single function.",
-  "1": "Expected the enhancer to be a function.",
-  "2": "Expected the reducer to be a function.",
+  "0": "It looks like you are passing several store enhancers to createStore(). This is not supported. Instead, compose them together to a single function. See https://redux.js.org/tutorials/fundamentals/part-4-store#creating-a-store-with-enhancers for an example.",
+  "1": "Expected the enhancer to be a function. Instead, received: ''",
+  "2": "Expected the root reducer to be a function. Instead, received: ''",
   "3": "You may not call store.getState() while the reducer is executing. The reducer has already received the state as an argument. Pass it down from the top reducer instead of reading it from the store.",
-  "4": "Expected the listener to be a function.",
+  "4": "Expected the listener to be a function. Instead, received: ''",
   "5": "You may not call store.subscribe() while the reducer is executing. If you would like to be notified after the store has been updated, subscribe from a component and invoke store.getState() in the callback to access the latest state. See https://redux.js.org/api/store#subscribelistener for more details.",
   "6": "You may not unsubscribe from a store listener while the reducer is executing. See https://redux.js.org/api/store#subscribelistener for more details.",
-  "7": "Actions must be plain objects. Use custom middleware for async actions.",
-  "8": "Actions may not have an undefined \"type\" property. Have you misspelled a constant?",
+  "7": "Actions must be plain objects. Instead, the actual type was: ''. You may need to add middleware to your store setup to handle dispatching other values, such as 'redux-thunk' to handle dispatching functions. See https://redux.js.org/tutorials/fundamentals/part-4-store#middleware and https://redux.js.org/tutorials/fundamentals/part-6-async-logic#using-the-redux-thunk-middleware for examples.",
+  "8": "Actions may not have an undefined \"type\" property. You may have misspelled an action type string constant.",
   "9": "Reducers may not dispatch actions.",
-  "10": "Expected the nextReducer to be a function.",
-  "11": "Expected the observer to be an object.",
-  "12": "bindActionCreators expected an object or a function, instead received . Did you write \"import ActionCreators from\" instead of \"import * as ActionCreators from\"?",
-  "13": "Dispatching while constructing your middleware is not allowed. Other middleware would not be applied to this dispatch.",
-  "14": "Reducer \"\" returned undefined during initialization. If the state passed to the reducer is undefined, you must explicitly return the initial state. The initial state may not be undefined. If you don't want to set a value for this reducer, you can use null instead of undefined.",
-  "15": "Reducer \"\" returned undefined when probed with a random type. Don't try to handle  or other actions in \"redux/*\" namespace. They are considered private. Instead, you must return the current state for any unknown actions, unless it is undefined, in which case you must return the initial state, regardless of the action type. The initial state may not be undefined, but can be null."
+  "10": "Expected the nextReducer to be a function. Instead, received: '",
+  "11": "Expected the observer to be an object. Instead, received: ''",
+  "12": "The slice reducer for key \"\" returned undefined during initialization. If the state passed to the reducer is undefined, you must explicitly return the initial state. The initial state may not be undefined. If you don't want to set a value for this reducer, you can use null instead of undefined.",
+  "13": "The slice reducer for key \"\" returned undefined when probed with a random type. Don't try to handle '' or other actions in \"redux/*\" namespace. They are considered private. Instead, you must return the current state for any unknown actions, unless it is undefined, in which case you must return the initial state, regardless of the action type. The initial state may not be undefined, but can be null.",
+  "14": "When called with an action of type , the slice reducer for key \"\" returned undefined. To ignore an action, you must explicitly return the previous state. If you want this reducer to hold no value, you can return null instead of undefined.",
+  "15": "Dispatching while constructing your middleware is not allowed. Other middleware would not be applied to this dispatch.",
+  "16": "bindActionCreators expected an object or a function, but instead received: ''. Did you write \"import ActionCreators from\" instead of \"import * as ActionCreators from\"?"
 }

src/bindActionCreators.js

@@ -1,3 +1,5 @@
+import { kindOf } from './utils/kindOf'
+
 function bindActionCreator(actionCreator, dispatch) {
   return function () {
     return dispatch(actionCreator.apply(this, arguments))
@@ -32,9 +34,9 @@ export default function bindActionCreators(actionCreators, dispatch) {
 
   if (typeof actionCreators !== 'object' || actionCreators === null) {
     throw new Error(
-      `bindActionCreators expected an object or a function, instead received ${
-        actionCreators === null ? 'null' : typeof actionCreators
-      }. ` +
+      `bindActionCreators expected an object or a function, but instead received: '${kindOf(
+        actionCreators
+      )}'. ` +
         `Did you write "import ActionCreators from" instead of "import * as ActionCreators from"?`
     )
   }

src/combineReducers.js

@@ -1,18 +1,7 @@
 import ActionTypes from './utils/actionTypes'
 import warning from './utils/warning'
 import isPlainObject from './utils/isPlainObject'
-
-function getUndefinedStateErrorMessage(key, action) {
-  const actionType = action && action.type
-  const actionDescription =
-    (actionType && `action "${String(actionType)}"`) || 'an action'
-
-  return (
-    `Given ${actionDescription}, reducer "${key}" returned undefined. ` +
-    `To ignore an action, you must explicitly return the previous state. ` +
-    `If you want this reducer to hold no value, you can return null instead of undefined.`
-  )
-}
+import { kindOf } from './utils/kindOf'
 
 function getUnexpectedStateShapeWarningMessage(
   inputState,
@@ -35,9 +24,9 @@ function getUnexpectedStateShapeWarningMessage(
 
   if (!isPlainObject(inputState)) {
     return (
-      `The ${argumentName} has unexpected type of "` +
-      {}.toString.call(inputState).match(/\s([a-z|A-Z]+)/)[1] +
-      `". Expected argument to be an object with the following ` +
+      `The ${argumentName} has unexpected type of "${kindOf(
+        inputState
+      )}". Expected argument to be an object with the following ` +
       `keys: "${reducerKeys.join('", "')}"`
     )
   }
@@ -69,7 +58,7 @@ function assertReducerShape(reducers) {
 
     if (typeof initialState === 'undefined') {
       throw new Error(
-        `Reducer "${key}" returned undefined during initialization. ` +
+        `The slice reducer for key "${key}" returned undefined during initialization. ` +
           `If the state passed to the reducer is undefined, you must ` +
           `explicitly return the initial state. The initial state may ` +
           `not be undefined. If you don't want to set a value for this reducer, ` +
@@ -83,8 +72,8 @@ function assertReducerShape(reducers) {
       }) === 'undefined'
     ) {
       throw new Error(
-        `Reducer "${key}" returned undefined when probed with a random type. ` +
-          `Don't try to handle ${ActionTypes.INIT} or other actions in "redux/*" ` +
+        `The slice reducer for key "${key}" returned undefined when probed with a random type. ` +
+          `Don't try to handle '${ActionTypes.INIT}' or other actions in "redux/*" ` +
           `namespace. They are considered private. Instead, you must return the ` +
           `current state for any unknown actions, unless it is undefined, ` +
           `in which case you must return the initial state, regardless of the ` +
@@ -167,8 +156,14 @@ export default function combineReducers(reducers) {
       const previousStateForKey = state[key]
       const nextStateForKey = reducer(previousStateForKey, action)
       if (typeof nextStateForKey === 'undefined') {
-        const errorMessage = getUndefinedStateErrorMessage(key, action)
-        throw new Error(errorMessage)
+        const actionType = action && action.type
+        throw new Error(
+          `When called with an action of type ${
+            actionType ? `"${String(actionType)}"` : '(unknown type)'
+          }, the slice reducer for key "${key}" returned undefined. ` +
+            `To ignore an action, you must explicitly return the previous state. ` +
+            `If you want this reducer to hold no value, you can return null instead of undefined.`
+        )
       }
       nextState[key] = nextStateForKey
       hasChanged = hasChanged || nextStateForKey !== previousStateForKey

src/createStore.js

@@ -2,6 +2,7 @@ import $$observable from 'symbol-observable'
 
 import ActionTypes from './utils/actionTypes'
 import isPlainObject from './utils/isPlainObject'
+import { kindOf } from './utils/kindOf'
 
 /**
  * Creates a Redux store that holds the state tree.
@@ -36,7 +37,7 @@ export default function createStore(reducer, preloadedState, enhancer) {
     throw new Error(
       'It looks like you are passing several store enhancers to ' +
         'createStore(). This is not supported. Instead, compose them ' +
-        'together to a single function.'
+        'together to a single function. See https://redux.js.org/tutorials/fundamentals/part-4-store#creating-a-store-with-enhancers for an example.'
     )
   }
 
@@ -47,14 +48,22 @@ export default function createStore(reducer, preloadedState, enhancer) {
 
   if (typeof enhancer !== 'undefined') {
     if (typeof enhancer !== 'function') {
-      throw new Error('Expected the enhancer to be a function.')
+      throw new Error(
+        `Expected the enhancer to be a function. Instead, received: '${kindOf(
+          enhancer
+        )}'`
+      )
     }
 
     return enhancer(createStore)(reducer, preloadedState)
   }
 
   if (typeof reducer !== 'function') {
-    throw new Error('Expected the reducer to be a function.')
+    throw new Error(
+      `Expected the root reducer to be a function. Instead, received: '${kindOf(
+        reducer
+      )}'`
+    )
   }
 
   let currentReducer = reducer
@@ -118,7 +127,11 @@ export default function createStore(reducer, preloadedState, enhancer) {
    */
   function subscribe(listener) {
     if (typeof listener !== 'function') {
-      throw new Error('Expected the listener to be a function.')
+      throw new Error(
+        `Expected the listener to be a function. Instead, received: '${kindOf(
+          listener
+        )}'`
+      )
     }
 
     if (isDispatching) {
@@ -184,15 +197,15 @@ export default function createStore(reducer, preloadedState, enhancer) {
   function dispatch(action) {
     if (!isPlainObject(action)) {
       throw new Error(
-        'Actions must be plain objects. ' +
-          'Use custom middleware for async actions.'
+        `Actions must be plain objects. Instead, the actual type was: '${kindOf(
+          action
+        )}'. You may need to add middleware to your store setup to handle dispatching other values, such as 'redux-thunk' to handle dispatching functions. See https://redux.js.org/tutorials/fundamentals/part-4-store#middleware and https://redux.js.org/tutorials/fundamentals/part-6-async-logic#using-the-redux-thunk-middleware for examples.`
       )
     }
 
     if (typeof action.type === 'undefined') {
       throw new Error(
-        'Actions may not have an undefined "type" property. ' +
-          'Have you misspelled a constant?'
+        'Actions may not have an undefined "type" property. You may have misspelled an action type string constant.'
       )
     }
 
@@ -228,7 +241,11 @@ export default function createStore(reducer, preloadedState, enhancer) {
    */
   function replaceReducer(nextReducer) {
     if (typeof nextReducer !== 'function') {
-      throw new Error('Expected the nextReducer to be a function.')
+      throw new Error(
+        `Expected the nextReducer to be a function. Instead, received: '${kindOf(
+          nextReducer
+        )}`
+      )
     }
 
     currentReducer = nextReducer
@@ -259,7 +276,11 @@ export default function createStore(reducer, preloadedState, enhancer) {
        */
       subscribe(observer) {
         if (typeof observer !== 'object' || observer === null) {
-          throw new TypeError('Expected the observer to be an object.')
+          throw new TypeError(
+            `Expected the observer to be an object. Instead, received: '${kindOf(
+              observer
+            )}'`
+          )
         }
 
         function observeState() {

src/utils/kindOf.js

@@ -0,0 +1,68 @@
+export function kindOf(val) {
+  let typeOfVal = typeof val
+
+  if (process.env.NODE_ENV !== 'production') {
+    // Inlined / shortened version of `kindOf` from https://github.com/jonschlinkert/kind-of
+    function miniKindOf(val) {
+      if (val === void 0) return 'undefined'
+      if (val === null) return 'null'
+
+      const type = typeof val
+      switch (type) {
+        case 'boolean':
+        case 'string':
+        case 'number':
+        case 'symbol':
+        case 'function': {
+          return type
+        }
+        default: break;
+      }
+
+      if (Array.isArray(val)) return 'array'
+      if (isDate(val)) return 'date'
+      if (isError(val)) return 'error'
+
+      const constructorName = ctorName(val)
+      switch (constructorName) {
+        case 'Symbol':
+        case 'Promise':
+        case 'WeakMap':
+        case 'WeakSet':
+        case 'Map':
+        case 'Set':
+          return constructorName
+        default: break;
+      }
+
+      // other
+      return type.slice(8, -1).toLowerCase().replace(/\s/g, '')
+    }
+
+    function ctorName(val) {
+      return typeof val.constructor === 'function' ? val.constructor.name : null
+    }
+
+    function isError(val) {
+      return (
+        val instanceof Error ||
+        (typeof val.message === 'string' &&
+          val.constructor &&
+          typeof val.constructor.stackTraceLimit === 'number')
+      )
+    }
+
+    function isDate(val) {
+      if (val instanceof Date) return true
+      return (
+        typeof val.toDateString === 'function' &&
+        typeof val.getDate === 'function' &&
+        typeof val.setDate === 'function'
+      )
+    }
+
+    typeOfVal = miniKindOf(val)
+  }
+
+  return typeOfVal
+}

test/bindActionCreators.spec.js

@@ -75,26 +75,26 @@ describe('bindActionCreators', () => {
     expect(() => {
       bindActionCreators(undefined, store.dispatch)
     }).toThrow(
-      'bindActionCreators expected an object or a function, instead received undefined. ' +
-        'Did you write "import ActionCreators from" instead of "import * as ActionCreators from"?'
+      `bindActionCreators expected an object or a function, but instead received: 'undefined'. ` +
+        `Did you write "import ActionCreators from" instead of "import * as ActionCreators from"?`
     )
   })
 
   it('throws for a null actionCreator', () => {
     expect(() => {
       bindActionCreators(null, store.dispatch)
     }).toThrow(
-      'bindActionCreators expected an object or a function, instead received null. ' +
-        'Did you write "import ActionCreators from" instead of "import * as ActionCreators from"?'
+      `bindActionCreators expected an object or a function, but instead received: 'null'. ` +
+        `Did you write "import ActionCreators from" instead of "import * as ActionCreators from"?`
     )
   })
 
   it('throws for a primitive actionCreator', () => {
     expect(() => {
       bindActionCreators('string', store.dispatch)
     }).toThrow(
-      'bindActionCreators expected an object or a function, instead received string. ' +
-        'Did you write "import ActionCreators from" instead of "import * as ActionCreators from"?'
+      `bindActionCreators expected an object or a function, but instead received: 'string'. ` +
+        `Did you write "import ActionCreators from" instead of "import * as ActionCreators from"?`
     )
   })
 })

test/combineReducers.spec.js

@@ -235,7 +235,7 @@ describe('Utils', () => {
 
       createStore(reducer, 1)
       expect(spy.mock.calls[2][0]).toMatch(
-        /createStore has unexpected type of "Number".*keys: "foo", "baz"/
+        /createStore has unexpected type of "number".*keys: "foo", "baz"/
       )
 
       reducer({ corge: 2 })
@@ -250,7 +250,7 @@ describe('Utils', () => {
 
       reducer(1)
       expect(spy.mock.calls[5][0]).toMatch(
-        /reducer has unexpected type of "Number".*keys: "foo", "baz"/
+        /reducer has unexpected type of "number".*keys: "foo", "baz"/
       )
 
       spy.mockClear()