Merge pull request #2041 from reduxjs/nullable-context

Author: markerikson

docs/api/Provider.md

@@ -39,9 +39,10 @@ interface ProviderProps<A extends Action = AnyAction, S = any> {
    * to create a context to be used.
    * If this is used, you'll need to customize `connect` by supplying the same
    * context provided to the Provider.
-   * Initial value doesn't matter, as it is overwritten with the internal state of Provider.
+   * Set the initial value to null, and the hooks will error
+   * if this is not overwritten by Provider.
    */
-  context?: Context<ReactReduxContextValue<S, A>>
+  context?: Context<ReactReduxContextValue<S, A> | null>
 
   /** Global configuration for the `useSelector` stability check */
   stabilityCheck?: StabilityCheck

docs/using-react-redux/accessing-store.md

@@ -27,7 +27,7 @@ Redux store accessible to deeply nested connected components. As of React Redux
 by a single default context object instance generated by `React.createContext()`, called `ReactReduxContext`.
 
 React Redux's `<Provider>` component uses `<ReactReduxContext.Provider>` to put the Redux store and the current store
-state into context, and `connect` uses `<ReactReduxContext.Consumer>` to read those values and handle updates.
+state into context, and `connect` uses `useContext(ReactReduxContext)` to read those values and handle updates.
 
 ## Using the `useStore` Hook
 
@@ -87,8 +87,8 @@ This also provides a natural isolation of the stores as they live in separate co
 
 ```js
 // a naive example
-const ContextA = React.createContext();
-const ContextB = React.createContext();
+const ContextA = React.createContext(null);
+const ContextB = React.createContext(null);
 
 // assuming reducerA and reducerB are proper reducer functions
 const storeA = createStore(reducerA);

src/components/Context.ts

@@ -19,20 +19,26 @@ const ContextKey = Symbol.for(`react-redux-context`)
 const gT: {
   [ContextKey]?: Map<
     typeof React.createContext,
-    Context<ReactReduxContextValue>
+    Context<ReactReduxContextValue | null>
   >
-} = (typeof globalThis !== "undefined" ? globalThis : /* fall back to a per-module scope (pre-8.1 behaviour) if `globalThis` is not available */ {}) as any; 
+} = (
+  typeof globalThis !== 'undefined'
+    ? globalThis
+    : /* fall back to a per-module scope (pre-8.1 behaviour) if `globalThis` is not available */ {}
+) as any
 
-function getContext(): Context<ReactReduxContextValue> {
+function getContext(): Context<ReactReduxContextValue | null> {
   if (!React.createContext) return {} as any
 
   const contextMap = (gT[ContextKey] ??= new Map<
     typeof React.createContext,
-    Context<ReactReduxContextValue>
+    Context<ReactReduxContextValue | null>
   >())
   let realContext = contextMap.get(React.createContext)
   if (!realContext) {
-    realContext = React.createContext<ReactReduxContextValue>(null as any)
+    realContext = React.createContext<ReactReduxContextValue | null>(
+      null as any
+    )
     if (process.env.NODE_ENV !== 'production') {
       realContext.displayName = 'ReactRedux'
     }

src/components/Provider.tsx

@@ -24,9 +24,10 @@ export interface ProviderProps<
   /**
    * Optional context to be used internally in react-redux. Use React.createContext() to create a context to be used.
    * If this is used, you'll need to customize `connect` by supplying the same context provided to the Provider.
-   * Initial value doesn't matter, as it is overwritten with the internal state of Provider.
+   * Set the initial value to null, and the hooks will error
+   * if this is not overwritten by Provider.
    */
-  context?: Context<ReactReduxContextValue<S, A>>
+  context?: Context<ReactReduxContextValue<S, A> | null>
 
   /** Global configuration for the `useSelector` stability check */
   stabilityCheck?: CheckFrequency

src/components/connect.tsx

@@ -584,7 +584,7 @@ function connect<
         : contextValue!.store
 
       const getServerState = didStoreComeFromContext
-        ? contextValue.getServerState
+        ? contextValue!.getServerState
         : store.getState
 
       const childPropsSelector = React.useMemo(() => {

src/hooks/useDispatch.ts

@@ -15,7 +15,7 @@ export function createDispatchHook<
   S = unknown,
   A extends Action<string> = UnknownAction
   // @ts-ignore
->(context?: Context<ReactReduxContextValue<S, A>> = ReactReduxContext) {
+>(context?: Context<ReactReduxContextValue<S, A> | null> = ReactReduxContext) {
   const useStore =
     // @ts-ignore
     context === ReactReduxContext ? useDefaultStore : createStoreHook(context)

src/hooks/useReduxContext.ts

@@ -10,7 +10,7 @@ import type { ReactReduxContextValue } from '../components/Context'
  * @returns {Function} A `useReduxContext` hook bound to the specified context.
  */
 export function createReduxContextHook(context = ReactReduxContext) {
-  return function useReduxContext(): ReactReduxContextValue | null {
+  return function useReduxContext(): ReactReduxContextValue {
     const contextValue = React.useContext(context)
 
     if (process.env.NODE_ENV !== 'production' && !contextValue) {
@@ -19,7 +19,7 @@ export function createReduxContextHook(context = ReactReduxContext) {
       )
     }
 
-    return contextValue
+    return contextValue!
   }
 }
 

src/hooks/useSelector.ts

@@ -43,7 +43,10 @@ const refEquality: EqualityFn<any> = (a, b) => a === b
  * @returns {Function} A `useSelector` hook bound to the specified context.
  */
 export function createSelectorHook(
-  context: React.Context<ReactReduxContextValue<any, any>> = ReactReduxContext
+  context: React.Context<ReactReduxContextValue<
+    any,
+    any
+  > | null> = ReactReduxContext
 ): UseSelector {
   const useReduxContext =
     context === ReactReduxContext
@@ -83,7 +86,7 @@ export function createSelectorHook(
       getServerState,
       stabilityCheck: globalStabilityCheck,
       noopCheck: globalNoopCheck,
-    } = useReduxContext()!
+    } = useReduxContext()
 
     const firstRun = React.useRef(true)
 

src/hooks/useStore.ts

@@ -17,7 +17,7 @@ export function createStoreHook<
   S = unknown,
   A extends BasicAction = UnknownAction
   // @ts-ignore
->(context?: Context<ReactReduxContextValue<S, A>> = ReactReduxContext) {
+>(context?: Context<ReactReduxContextValue<S, A> | null> = ReactReduxContext) {
   const useReduxContext =
     // @ts-ignore
     context === ReactReduxContext
@@ -29,7 +29,7 @@ export function createStoreHook<
     Action2 extends BasicAction = A
     // @ts-ignore
   >() {
-    const { store } = useReduxContext()!
+    const { store } = useReduxContext()
     // @ts-ignore
     return store as Store<State, Action2>
   }

test/components/connect.spec.tsx

@@ -2130,9 +2130,10 @@ describe('React', () => {
           }
         }
 
-        const context = React.createContext<
-          ReactReduxContextValue<any, AnyAction>
-        >(null as any)
+        const context = React.createContext<ReactReduxContextValue<
+          any,
+          AnyAction
+        > | null>(null)
 
         let actualState
 
@@ -2171,9 +2172,10 @@ describe('React', () => {
           }
         }
 
-        const context = React.createContext<
-          ReactReduxContextValue<any, AnyAction>
-        >(null as any)
+        const context = React.createContext<ReactReduxContextValue<
+          any,
+          AnyAction
+        > | null>(null)
 
         let actualState
 
@@ -2421,9 +2423,8 @@ describe('React', () => {
           (state: RootStateType = 0, action: ActionType) =>
             action.type === 'INC' ? state + 1 : state
         )
-        const customContext = React.createContext<ReactReduxContextValue>(
-          null as any
-        )
+        const customContext =
+          React.createContext<ReactReduxContextValue | null>(null)
 
         class A extends Component {
           render() {

test/hooks/useDispatch.spec.tsx

@@ -27,9 +27,8 @@ describe('React', () => {
     })
     describe('createDispatchHook', () => {
       it("returns the correct store's dispatch function", () => {
-        const nestedContext = React.createContext<ReactReduxContextValue>(
-          null as any
-        )
+        const nestedContext =
+          React.createContext<ReactReduxContextValue | null>(null)
         const useCustomDispatch = createDispatchHook(nestedContext)
         const { result } = renderHook(() => useDispatch(), {
           // eslint-disable-next-line react/prop-types

test/hooks/useReduxContext.spec.tsx

@@ -1,6 +1,6 @@
 import { renderHook } from '@testing-library/react-hooks'
 import { createContext } from 'react'
-import { ReactReduxContextValue } from '../../src/components/Context'
+import type { ReactReduxContextValue } from '../../src/components/Context'
 import {
   createReduxContextHook,
   useReduxContext,
@@ -23,7 +23,7 @@ describe('React', () => {
     })
     describe('createReduxContextHook', () => {
       it('throws if component is not wrapped in provider', () => {
-        const customContext = createContext<ReactReduxContextValue>(null as any)
+        const customContext = createContext<ReactReduxContextValue | null>(null)
         const useCustomReduxContext = createReduxContextHook(customContext)
         const spy = jest.spyOn(console, 'error').mockImplementation(() => {})
 

test/hooks/useSelector.spec.tsx

@@ -153,8 +153,8 @@ describe('React', () => {
           }
 
           const Parent = () => {
-            const { subscription } = useContext(ReactReduxContext)
-            appSubscription = subscription
+            const contextVal = useContext(ReactReduxContext)
+            appSubscription = contextVal && contextVal.subscription
             const count = useNormalSelector((s) => s.count)
             return count === 1 ? <Child /> : null
           }
@@ -179,8 +179,8 @@ describe('React', () => {
           let appSubscription: Subscription | null = null
 
           const Parent = () => {
-            const { subscription } = useContext(ReactReduxContext)
-            appSubscription = subscription
+            const contextVal = useContext(ReactReduxContext)
+            appSubscription = contextVal && contextVal.subscription
             const count = useNormalSelector((s) => s.count)
             return count === 0 ? <Child /> : null
           }
@@ -944,9 +944,8 @@ describe('React', () => {
       })
 
       it('subscribes to the correct store', () => {
-        const nestedContext = React.createContext<ReactReduxContextValue>(
-          null as any
-        )
+        const nestedContext =
+          React.createContext<ReactReduxContextValue | null>(null)
         const useCustomSelector = createSelectorHook(nestedContext)
         let defaultCount: number | null = null
         let customCount: number | null = null

test/typetests/connect-mapstate-mapdispatch.tsx

@@ -2,27 +2,25 @@
 
 import * as React from 'react'
 import * as ReactDOM from 'react-dom'
+import type { Dispatch, ActionCreator } from 'redux'
 import {
   Store,
-  Dispatch,
   AnyAction,
-  ActionCreator,
   createStore,
   bindActionCreators,
   ActionCreatorsMapObject,
   Reducer,
 } from 'redux'
+import type { ReactReduxContext, MapDispatchToProps } from '../../src/index'
 import {
   connect,
   ConnectedProps,
   Provider,
   DispatchProp,
   MapStateToProps,
-  ReactReduxContext,
   ReactReduxContextValue,
   Selector,
   shallowEqual,
-  MapDispatchToProps,
   useDispatch,
   useSelector,
   useStore,

test/typetests/connect-options-and-issues.tsx

@@ -2,23 +2,17 @@
 import * as PropTypes from 'prop-types'
 import * as React from 'react'
 import * as ReactDOM from 'react-dom'
-import {
-  Store,
-  Dispatch,
-  AnyAction,
-  ActionCreator,
-  createStore,
-  bindActionCreators,
-  ActionCreatorsMapObject,
-  Reducer,
-} from 'redux'
-import {
-  connect,
+import type { Store, Dispatch, AnyAction, ActionCreator, Reducer } from 'redux'
+import { createStore, bindActionCreators, ActionCreatorsMapObject } from 'redux'
+import type {
   Connect,
   ConnectedProps,
-  Provider,
   DispatchProp,
   MapStateToProps,
+} from '../../src/index'
+import {
+  connect,
+  Provider,
   ReactReduxContext,
   ReactReduxContextValue,
   Selector,

test/typetests/hooks.tsx

@@ -2,16 +2,20 @@
 
 import * as React from 'react'
 import * as ReactDOM from 'react-dom'
-import { Store, Dispatch, configureStore, AnyAction } from '@reduxjs/toolkit'
+import type { Store, Dispatch, AnyAction } from '@reduxjs/toolkit'
+import { configureStore } from '@reduxjs/toolkit'
+import type {
+  ReactReduxContextValue,
+  Selector,
+  TypedUseSelectorHook,
+} from '../../src/index'
 import {
   connect,
   ConnectedProps,
   Provider,
   DispatchProp,
   MapStateToProps,
   ReactReduxContext,
-  ReactReduxContextValue,
-  Selector,
   shallowEqual,
   MapDispatchToProps,
   useDispatch,
@@ -20,17 +24,15 @@ import {
   createDispatchHook,
   createSelectorHook,
   createStoreHook,
-  TypedUseSelectorHook,
 } from '../../src/index'
 
+import type { AppDispatch, RootState } from './counterApp'
 import {
   CounterState,
   counterSlice,
   increment,
   incrementAsync,
-  AppDispatch,
   AppThunk,
-  RootState,
   fetchCount,
 } from './counterApp'
 
@@ -224,9 +226,10 @@ function testCreateHookFunctions() {
     type: 'TEST_ACTION'
   }
 
-  const Context = React.createContext<
-    ReactReduxContextValue<RootState, RootAction>
-  >(null as any)
+  const Context = React.createContext<ReactReduxContextValue<
+    RootState,
+    RootAction
+  > | null>(null)
 
   // No context tests
   expectType<() => Dispatch<AnyAction>>(createDispatchHook())