如何保证 promise 永远不会拒绝的 API 用户

Question

I have a promise returning function and that promise never rejects I always handle all errors and still resolve a value. I want to inform the user that s/he doesn't have to append catch function to the promise.

const createItem = (name: string): Promise<boolean> => {
   return new Promise<boolean>(resolve => {
       someAjaxCall().then(response => {
           if (response.status >= 200 && response.status < 300) {
              resolve(true);
           } else {
              handleError();    // some logging to console
              resolve(false);
           }
       }).catch(error => {
           handleError();    // some logging to console
           resolve(false);
       });
   });
} 

Actually changing return type to Promise<void> and replacing resolve(true) parts with resolve() and replacing resolve(false) parts with reject() solves my problem.

But I want to know that is there any other elegant way to tell the API user that "you won't ever need to append catch and you must handle exactly these values in your then".

Answer 1

But I want to know that is there any other elegant way to tell the API user that "you won't ever need to append catch and you must handle exactly these values in your then".

No. Similar to the fact that there is no way in the type system to say a function never throws there is no way for promise never rejects .

Your only option is to add documentation for this fact if you want