| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | */ |
| 7 | |
| 8 | import React from 'react'; |
| 9 | |
| 10 | /** |
| 11 | * Replacement to React.createContext. |
| 12 | * |
| 13 | * Does not take any default value and avoids non-null assertions when using |
| 14 | * the value of the context, like the following scenario. |
| 15 | * |
| 16 | * ```ts |
| 17 | * const StoreDispatchContext = useContext<Dispatch<ReducerAction>>(null); |
| 18 | * const dispatchStore = useContext(StoreDispatchContext); |
| 19 | * ... |
| 20 | * dipatchStore!({ ... }); |
| 21 | * ``` |
| 22 | * |
| 23 | * Instead, it throws an error when `useContext` is not called within a |
| 24 | * Provider with a value. |
| 25 | */ |
| 26 | export default function createContext<T>(): { |
| 27 | useContext: () => NonNullable<T>; |
| 28 | Provider: React.Provider<T | null>; |
| 29 | } { |
| 30 | const context = React.createContext<T | null>(null); |
| 31 | |
| 32 | function useContext(): NonNullable<T> { |
| 33 | const c = React.useContext(context); |
| 34 | if (!c) |
| 35 | throw new Error('useContext must be within a Provider with a value'); |
| 36 | return c; |
| 37 | } |
| 38 | |
| 39 | return {useContext, Provider: context.Provider}; |
| 40 | } |