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- import {PromiseValue} from './promise-value';
- import {SetReturnType} from './set-return-type';
-
- /**
- Create an async version of the given function type, by boxing the return type in `Promise` while keeping the same parameter types.
-
- Use-case: You have two functions, one synchronous and one asynchronous that do the same thing. Instead of having to duplicate the type definition, you can use `Asyncify` to reuse the synchronous type.
-
- @example
- ```
- import {Asyncify} from 'type-fest';
-
- // Synchronous function.
- function getFooSync(someArg: SomeType): Foo {
- // …
- }
-
- type AsyncifiedFooGetter = Asyncify<typeof getFooSync>;
- //=> type AsyncifiedFooGetter = (someArg: SomeType) => Promise<Foo>;
-
- // Same as `getFooSync` but asynchronous.
- const getFooAsync: AsyncifiedFooGetter = (someArg) => {
- // TypeScript now knows that `someArg` is `SomeType` automatically.
- // It also knows that this function must return `Promise<Foo>`.
- // If you have `@typescript-eslint/promise-function-async` linter rule enabled, it will even report that "Functions that return promises must be async.".
-
- // …
- }
- ```
- */
- export type Asyncify<Fn extends (...args: any[]) => any> = SetReturnType<Fn, Promise<PromiseValue<ReturnType<Fn>>>>;
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