Enhance ES6 Promises with TypeScript overrides using Bluebird

Question

Enhance ES6 Promises with TypeScript overrides using Bluebird

I am encountering a challenge with a Node.js library that utilizes promises, specifically TypeScript declarations using ES6 Promise. Interestingly, this library can be adjusted to work with any promise library, such as Bluebird.

The issue lies in making the Bluebird promise interface accessible at a declarative level without modifying the library itself. Is there a method to communicate to the compiler that a different Promise protocol is being used?

Naturally, altering the library directly would resolve this dilemma effortlessly. However, that option is not viable in this scenario.

To provide insight into the nature of this library, consider the following simplistic interface example:

interface Protocol {
    methodName(param1:string, param2:number):Promise<Object[]>
}

This interface complexity is then amplified by a factor of 1000.

Creating a mock protocol in a separate file will not suffice. The key is determining how to specify to the compiler that the default ES6 Promise should be replaced with the Bluebird TypeScript version.

typescript bluebird

Answer 1

Answer №1

If you want to modify the Promise type, one way to do it is by using a union. You can find more information on union types here.

While this approach works, it is not recommended

import Bluebird from 'bluebird';

type Promise = Promise | Bluebird;

As suggested in the comment by @Paarth, a better way would be to typecast your Bluebird promise to an ES6 Promise.

This is the preferred method

If you have a third-party library with a structure like:

interface Protocol {
    methodName(param1:string, param2:number):Promise<Object[]>
}

You could use it in the following way:

import Bluebird from 'bluebird';

class Http implements Protocol {
  methodName(url: string, payload: number): Promise<Object[]> {
    return <Promise<Object[]>>new Bluebird((resolve, reject) => {

      // Perform necessary actions with the url and payload

      resolve([{ data: 'Done' }]);
    });
  }
}

let http = new Http();

http.methodName('//get-some-data', 10);

Note: This code snippet has not been tested through compilation due to lack of environment setup, and issues with the Typescript compiler in jsbin

Answer 2

If you want to modify the Promise type, one way to do it is by using a union. You can find more information on union types here.

While this approach works, it is not recommended

import Bluebird from 'bluebird';

type Promise = Promise | Bluebird;

As suggested in the comment by @Paarth, a better way would be to typecast your Bluebird promise to an ES6 Promise.

This is the preferred method

If you have a third-party library with a structure like:

interface Protocol {
    methodName(param1:string, param2:number):Promise<Object[]>
}

You could use it in the following way:

import Bluebird from 'bluebird';

class Http implements Protocol {
  methodName(url: string, payload: number): Promise<Object[]> {
    return <Promise<Object[]>>new Bluebird((resolve, reject) => {

      // Perform necessary actions with the url and payload

      resolve([{ data: 'Done' }]);
    });
  }
}

let http = new Http();

http.methodName('//get-some-data', 10);

Note: This code snippet has not been tested through compilation due to lack of environment setup, and issues with the Typescript compiler in jsbin

Enhance ES6 Promises with TypeScript overrides using Bluebird

Answer №1

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