TypeScript correctly type a queryresult MySQL - mysql

Question

I am using the mysql2/promise npm package for connecting and doing queries to a MySQL database. I got confused trying to set the correct typing for my query result, because I don't know in advance what type the result will be.
I have created a database class that has an async query method.
// Database.ts
import mysql, { Pool } from "mysql2/promise"; // import mysql2/promise
export class Database implements IDatabase {
logger: ILogger;
pool: Pool;
constructor(logger: ILogger) {
this.logger = logger;
// pool connection is set up here
}
async query(sql: string, options?: unknown): Promise<unknown> { // type?
const [rows] = await this.pool.query(sql, options);
return rows;
}
}
In my server code, I would like to be able do something like this:
// server.ts
import { Database } from "./core/Database";
const db = new Database(logger);
app.get("/", async (req, res) => {
const sql = `
select *
from users;
`;
const users: IUser[] = await db.query(sql); // get people
// do some logic x
// send response
res.json({
result: x
});
});
Using unknown doesn't work because I can't assign it to my type, using any does, but feels wrong. Is there a clean way to do this?

Answer 1

Type the function as:
async query<T = unknown>(sql: string, options?: unknown): Promise<T[]> {
Then use the function this way:
const users = await db.query<IUser>(sql);

Answer 2

With help of #Evert and this answer, I found a solution
I created following types:
export type DbDefaults = RowDataPacket[] | RowDataPacket[][] | OkPacket[] | OkPacket;
export type DbQueryResult<T> = T & DbDefaults;
Rewrote my method like this:
async query<T>(sql: string, options?: unknown): Promise<DbQueryResult<T[]>> {
const [result] = await this.pool.query<DbQueryResult<T[]>>(sql, options);
return result;
}
I can use it like this now:
const sql = `
select *
from users;
`;
const people = await db.query<IUser>(sql);
Just casting as T is also possible.
public async query<T>(sql: QueryString, parameters?: unknown[]): Promise<T[]> {
const [rows] = await this.pool.query(sql, parameters);
return rows as T[];
}