TypeScript 类型用于扩展内置节点类型的 package

Question

I'm trying to create full typings for https://www.npmjs.com/package/keypress

I've got the basic function typed out correctly (I think) but can't figure out how to extend the declaration of process.stdin as this package does to make IntelliSense happy.

Specifically, keypress adds a process.stdin.on('keypress', listener) event. The listener has signature like (ch: Ch, key?: Key) => void .

I'm not sure if I need to extend the Process interface or maybe the ReadStream interface since, in theory if I'm understanding correctly, it could work on any ReadStream .

I'm also not sure if it's possible to inform TypeScript that it's calling keypress() on a ReadStream that adds the functionality. For instance, preventing access unless keypress() was called. I doubt this is possible but asking in case it could be.

Here is my current attempt:

declare module "keypress" {
  export default function keypress(stream: NodeJS.ReadStream): void;

  export type Ch = any; // TODO
  export type Key = {
    // TODO
    ctrl: any;
    name: string;
  };

  namespace global {
    namespace NodeJS {
      interface Process {
        stdin: NodeJS.ReadStream & {
          fd: 0; // From official node types
          on(event: "keypress", listener: (ch: Ch, key?: Key) => void): this;
        };
      }
    }
  }
}

I've tried a few variations on this but I'd rather not keep shooting blind. Any pointers on this greatly appreciated. Cheers!

Answer 1

Looking at the official node type definitions this is what you are trying to extend: https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/node/process.d.ts#L217

Your approach looks fine to me, however I don't think this can be done at the moment. You can use declaration merging to extend types, but you can't use it to overwrite existing members of types. Otherwise several type definitions could be in conflict with one another.

However there is a discussion about implementing a solution here: https://github.com/microsoft/TypeScript/issues/36146