Solving the TS2769 Error in Upstash

Planted September 10, 2023

Upstash is a serverless data platform that supports Redis and Kafka. It is a great tool for building serverless applications. However, when I was trying to use it in my project, I encountered a TypeScript error TS2769: No overload matches this call.. This article will show you how to solve this error.

Setting Sail with Upstash

Upstash provides a Node.js package @upstash/redis that allows you to connect to Upstash Redis instances, along with some example code to get you started:

import { Redis } from '@upstash/redis'

const redis = new Redis({
  url: 'https://eu1-example.upstash.io',
  token: '********',
})
   
const data = await redis.set('foo', 'bar');

It is not recommended to hardcode the URL and token in the code, so it’s butter put them in .env.local instead:

UPSTASH_REDIS_REST_URL=https://eu1-example.upstash.io
UPSTASH_REDIS_REST_TOKEN=********

And then use process.env to access them:

import { Redis } from '@upstash/redis'

const redis = new Redis({
  url: process.env.UPSTASH_REDIS_REST_URL,
  token: process.env.UPSTASH_REDIS_REST_TOKEN,
})

const data = await redis.set('foo', 'bar');

Unexpected Error TS2769

After setting up the Upstash Redis client, I noticed that my IDE (WebStorm) is showing an error:

TS2769: No overload matches this call.   
Overload 1 of 2, '(config: RedisConfigNodejs): Redis', gave the following error.     
Type 'string | undefined' is not assignable to type 'string'.       
Type 'undefined' is not assignable to type 'string'.   

Overload 2 of 2, '(requesters: Requester): Redis', gave the following error.     
Argument of type '{ url: string | undefined; token: string; }' is not assignable to parameter of type 'Requester'.       
Object literal may only specify known properties, and 'url' does not exist in type 'Requester'. 

nodejs.d.ts(12, 5): The expected type comes from property 'url' which is declared here on type 'RedisConfigNodejs'

The error message indicated that the types string | undefined is not assignable to type string. This is because the environment variable returned by process.env is of type string | undefined, and the RedisConfigNodejs type only accepts string as the url property.

The Solution

The solution to this problem is simple:

const redis = Redis.fromEnv();

The fromEnv method will read the UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN environment variables and return a Redis instance.

It does the validation for you, so you don’t have to worry about the types:

// source: upstash-redis/platforms/nodejs.ts
/**
   * Create a new Upstash Redis instance from environment variables.
   *
   * Use this to automatically load connection secrets from your environment
   * variables. For instance when using the Vercel integration.
   *
   * This tries to load `UPSTASH_REDIS_REST_URL` and `UPSTASH_REDIS_REST_TOKEN` from
   * your environment using `process.env`.
   */
  static fromEnv(config?: Omit<RedisConfigNodejs, "url" | "token">): Redis {
    // @ts-ignore process will be defined in node
    if (typeof process?.env === "undefined") {
      throw new Error(
        'Unable to get environment variables, `process.env` is undefined. If you are deploying to cloudflare, please import from "@upstash/redis/cloudflare" instead',
      );
    }
    // @ts-ignore process will be defined in node
    const url = process?.env["UPSTASH_REDIS_REST_URL"];
    if (!url) {
      throw new Error(
        "Unable to find environment variable: `UPSTASH_REDIS_REST_URL`",
      );
    }
    // @ts-ignore process will be defined in node
    const token = process?.env["UPSTASH_REDIS_REST_TOKEN"];
    if (!token) {
      throw new Error(
        "Unable to find environment variable: `UPSTASH_REDIS_REST_TOKEN`",
      );
    }
    return new Redis({ ...config, url, token });
  }
}

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