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26 lines
1.2 KiB
26 lines
1.2 KiB
// tslint:disable:max-line-length
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// credits: https://stackoverflow.com/questions/49998665/promisified-function-type
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// Generic Function definition
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type AnyFunction = (...args: any[]) => any;
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// Extracts the type if wrapped by a Promise
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type Unpacked<T> = T extends Promise<infer U> ? U : T;
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type PromisifiedFunction<T extends AnyFunction> =
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T extends () => infer U ? () => Promise<Unpacked<U>> :
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T extends (a1: infer A1) => infer U ? (a1: A1) => Promise<Unpacked<U>> :
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T extends (a1: infer A1, a2: infer A2) => infer U ? (a1: A1, a2: A2) => Promise<Unpacked<U>> :
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T extends (a1: infer A1, a2: infer A2, a3: infer A3) => infer U ? (a1: A1, a2: A2, a3: A3) => Promise<Unpacked<U>> :
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T extends (a1: infer A1, a2: infer A2, a3: infer A3, a4: infer A4) => infer U ? (a1: A1, a2: A2, a3: A3, a4: A4) => Promise<Unpacked<U>> :
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// ...
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T extends (...args: any[]) => infer U ? (...args: any[]) => Promise<Unpacked<U>> : T;
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/**
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* `Promisified<T>` has the same methods as `T` but they all return promises. This is useful when
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* creating a stub with `grain-rpc` for an api which is synchronous.
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*/
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export type Promisified<T> = {
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[K in keyof T]: T[K] extends AnyFunction ? PromisifiedFunction<T[K]> : never
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};
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