32 lines
1.2 KiB
TypeScript
Executable file
32 lines
1.2 KiB
TypeScript
Executable file
import {PromiseValue} from './promise-value';
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import {SetReturnType} from './set-return-type';
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/**
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Create an async version of the given function type, by boxing the return type in `Promise` while keeping the same parameter types.
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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.
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@example
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```
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import {Asyncify} from 'type-fest';
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// Synchronous function.
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function getFooSync(someArg: SomeType): Foo {
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// …
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}
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type AsyncifiedFooGetter = Asyncify<typeof getFooSync>;
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//=> type AsyncifiedFooGetter = (someArg: SomeType) => Promise<Foo>;
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// Same as `getFooSync` but asynchronous.
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const getFooAsync: AsyncifiedFooGetter = (someArg) => {
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// TypeScript now knows that `someArg` is `SomeType` automatically.
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// It also knows that this function must return `Promise<Foo>`.
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// If you have `@typescript-eslint/promise-function-async` linter rule enabled, it will even report that "Functions that return promises must be async.".
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// …
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}
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```
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*/
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export type Asyncify<Fn extends (...args: any[]) => any> = SetReturnType<Fn, Promise<PromiseValue<ReturnType<Fn>>>>;
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