The return type for the request handler should be a response handler and not void.

[LuisAverhoff]

There is a type error that occurs if you try to get the number of calls a handler has made. In the index.d.ts file, the return type for any request http verb is void, when in the actual source code it is a function that returns a handler; particularly, the handler that was passed to the register function. This handler is the one that maintains state of how many calls has been made. Here is an example of how it is being used in the READMe.md file.

server.get(/* ... */);
const handler = server.handlers[0]; // type error. handlers does not exist as a type for the server.

// or

const handler = server.get(/* ... */); // type error. http verb function returns void.

// then

const numberOfCalls = handler.numberOfCalls;

My suggestion is to change

export type RequestHandler = (
  urlExpression: string,
  response: ResponseHandler,
  asyncOrDelay?: boolean | number
) => void;

to

export type RequestHandler = (
  urlExpression: string,
  response: ResponseHandler,
  asyncOrDelay?: boolean | number
) => ResponseHandler;

For reference, here is what the verbify function is doing.

function verbify(verb) {
  return function(path, handler, async) {
    return this.register(verb, path, handler, async);
  };
}

and here is what the register function is doing.

 register: function register(verb, url, handler, async) {
    if (!handler) {
      throw new Error('The function you tried passing to Pretender to handle ' +
        verb + ' ' + url + ' is undefined or missing.');
    }

    handler.numberOfCalls = 0;
    handler.async = async;
    this.handlers.push(handler);

    var registry = this.hosts.forURL(url)[verb];

    registry.add([{
      path: parseURL(url).fullpath,
      handler: handler
    }]);

    return handler; // notice how we are returning a handler in the register function.
  },

Of course, that leaves the issue of the handler not having the properties numberOfCalls and async as those seem to get added dynamically.

So the interface for ResponseHandler will also need to get updated but I dont know much about the codebase to get this done smoothly. Hopefully it should not be to much work to add these missing properties to the handler.

[xg-wang]

@mike-north any idea how to address the dynamically added properties type?

[mike-north]

@xg-wang the easiest way to handle this would be something like

 register: function register(verb, url, handler: RequestHandler, async: Async) {
    // Locally, work with a value w/ optional properties
    const h: RequestHandler & { numberOfCalls?: number, async?: Async } = handler;
    h.numberOfCalls = 0;
    h.async = async;
    this.handlers.push(h);

    var registry = this.hosts.forURL(url)[verb];

    registry.add([{
      path: parseURL(url).fullpath,
      handler: h
    }]);
   // Ultimately return a type with non-optional extra properties
    return h as RequestHandler & { numberOfCalls: number; async: Async }
  },