Promisify in redis client violates eslint rules

Question

I wanted to use redis client with promisify:

import type { RedisClient } from "redis";
import * as util from "util";

class MyClass {
  private redisClient: RedisClient;

  constructor(client: RedisClient) {
    this.redisClient = client;
  }

  getMyData = (): SomeType[] => {
    const getAsync: Promise<string | undefined> = util.promisify(this.redisClient.get).bind(this.redisClient);
 // ...
  };
}

However I ran into two issues with eslint:

1. ESLint: Avoid referencing unbound methods which may cause unintentional scoping of 'this'.(@typescript-eslint/unbound-method) at this.redisClient.get fragment

and

2. ESLint: Unsafe assignment of an any value.(@typescript-eslint/no-unsafe-assignment) at getAsync

How I can use promisify in a way that will be type aware and proper this scoping?

Answer 1

In your first eslint error, you are binding this to the wrong method.

In the second error, you are telling Typescript what return type getAsync should hold, instead you need to tell promisify what is the return value that your are trying to promisify.

This should fix both eslint errors:

import type { RedisClient } from "redis";
import * as util from "util";

class MyClass {
  private redisClient: RedisClient;

  constructor(client: RedisClient) {
    this.redisClient = client;
  }

  getMyData = (): SomeType[] => {
    const getAsync = util.promisify<string |undefined>(this.redisClient.get.bind(this.redisClient))

  };
}