基于回调推断嵌套函数的typeof

Question

我正在尝试编写一个接受对象并返回嵌套函数的函数，该函数将接受回调并返回相同类型的函数。不幸的是，我无法以这种方式编写它，因此结果将具有与回调相同的类型

type Constructor<T> = new (...args: any[]) => T


export type Settings = {
   maxCalls: number
   interval: number
   errors: Constructor<Error>[]
}

export function withRetryDelayed<R, U extends any[]>({
   maxCalls = 2,
   interval = 100,
   errors = [Error]
}: Partial<Settings> = {}): (cb: (...args: U) => Promise<R>) => (...args: U) => Promise<R> {
   let calls = maxCalls
   return (callback: (...args: U) => Promise<R>): (...args: U) => Promise<R> => {
      const retrying = async (...args: U): Promise<R> => {
         try {
            return await callback(...args)
         } catch (err) {
            if (calls-- <= 1 || !errors.some(ErrorConstructor => err instanceof ErrorConstructor)) {
               throw err
            }
            return interval
               ? new Promise(resolve => {
                  setTimeout(() => resolve(retrying(...args)), (maxCalls - calls) * interval)
               })
               : retrying(...args)
         }
      }
      return retrying
   }
}

const theX = (a: string): Promise<string> => Promise.resolve(a)

class MockError1 extends Error { }



const withRetryCallback = withRetryDelayed({
   maxCalls: 10,
   errors: [MockError1]
})(theX)


// typeof withRetryCallback is (...args: any[]) => Promise<unknown>

Playground

Answer 1

只需在应用它们时添加泛型 - 在内部函数而不是外部函数上。这样您在应用设置后获得的功能是通用的，并且可以根据您提供的参数进行推断。

type Constructor<T> = new (...args: any[]) => T


export type Settings = {
   maxCalls: number
   interval: number
   errors: Constructor<Error>[]
}

export function withRetryDelayed({
   maxCalls = 2,
   interval = 100,
   errors = [Error]
}: Partial<Settings> = {}) {
   let calls = maxCalls
   return <R, U extends any[]>(callback: (...args: U) => Promise<R>): (...args: U) => Promise<R> => {
      const retrying = async (...args: U): Promise<R> => {
         try {
            return await callback(...args)
         } catch (err) {
            if (calls-- <= 1 || !errors.some(ErrorConstructor => err instanceof ErrorConstructor)) {
               throw err
            }
            return interval
               ? new Promise(resolve => {
                  setTimeout(() => resolve(retrying(...args)), (maxCalls - calls) * interval)
               })
               : retrying(...args)
         }
      }
      return retrying
   }
}

const theX = (a: string): Promise<string> => Promise.resolve(a)

class MockError1 extends Error { }

const withRetryCallback = withRetryDelayed({
   maxCalls: 10,
   errors: [MockError1]
})(theX);

// Now typeof withRetryCallback is (a: string) => Promise<string>