复杂类型层次结构将叶子映射到“未知”类型

Question

我正在尝试为 API 外观构建一个灵活的通用基类。这些外观将定义一组返回特定​​类型的 HTTP 请求。这些定义用于构建自定义的请求注册表并在每个外观的基础上进行跟踪。我希望这些请求能够提供所有类型信息，但是我认为我在映射类型方面遇到了问题，因为在其核心，我使用的是`FacadeResultTypes = Record;

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///////////////////
//  Types setup  //
///////////////////

// Convenience operator
type ValueOf<T> = T[keyof T];

// Describes an HTTP request's name and result type - implemented by an individual facade service.
// Note that the `unknown` type here is resulting in the issue.
type FacadeResultTypes = Record<string, unknown>;

// Defines a single type of request made by an API facade. Tracks number of inflight requests, errors, and latest value (value type is critical)
type FacadeRequest<T extends ValueOf<FacadeResultTypes>> = {
  inFlight: number;
  latest: T|undefined;
  error: string|undefined;
}

// A dictionary to look up FacadeRequests by name (name comes from the FacadeResultTypes keys, value is individual requests)
type FacadeRequestDictionary<ResultTypes extends FacadeResultTypes>
  = Record<keyof ResultTypes, FacadeRequest<ValueOf<ResultTypes>>>;

// Tracks the latest request to complete, as well as contains a FacadeRequestDictionary of all requests for the facade
type FacadeRequestRegistry<ResultTypes extends FacadeResultTypes> = {
  latest: FacadeRequest<ValueOf<ResultTypes>> | undefined;
  all: FacadeRequestDictionary<ResultTypes>;
}



/////////////////////
//  Example usage  //
/////////////////////

interface ExampleResponseType {
  test: string;
  test2: number;
}

interface ExampleFacadeResultTypes extends FacadeResultTypes {
  exampleRequest: ExampleResponseType;
  // other request name/response type pairs go in this list
}

const exampleRegistry: FacadeRequestRegistry<ExampleFacadeResultTypes> = {
  latest: undefined,
  all: {
    exampleRequest: {     // <-- Maps to facadeRequest<unknown>
      inFlight: 0,
      latest: undefined,  // <-- Maps to `unkonwn`
      error: undefined,
    }
    // Other request types defined in the ExampleFacadeResultTypes interface would show up here
  }
};

// PROBLEM:
// While exampleRegistry and exampleRegistry.all map to their correctly resolved types, exampleRegistry.all.exampleRequest maps to facadeRequest<unknown> and its child .latest also maps to unknown.
// I would like those `unknown` types to map to their corresponding FacadeResultTypes.

// Specifically, I want exampleRegistry.all.exampleRequest.latest to map to ExampleResponseType.
exampleRegistry.all.exampleRequest.latest;

正如您所看到的，我不希望 unknown （这需要实现者进行类型转换）出现在对层次结构中最低级别元素的最终引用中。

有人看到我在这里做错了什么吗？感谢您的任何帮助。

Answer 1

// Convenience operator
type ValueOf<T> = T[keyof T];

我不确定为什么你有这个 ValueOf 类型。那就行了：

Type A = { a: 1, b: 2 }
Type B = ValueOf<A> // 1 | 2

我不明白这对你的问题有什么帮助。

如果你完全删除它，我认为一切都会按你的预期进行。

exampleRegistry.all.exampleRequest.latest; //  ExampleFacadeResultTypes | undefined

参见游乐场