Why can't Pool be inherited?

[tulayang]

class MyPool extends require('pg').Pool {
  f() {
    console.log('...')
  }
}

var pool = new MyPool()
pool.f()

I got a TypeError:

TypeError: pool.f is not a function

[tulayang]

And the definition of @types/pg-pool is wrong:

/// <reference types="pg" />
export {Pool, PoolConfig } from "pg";

[charmander]

See #1541.

[tulayang]

@charmander

I see. Would it be a solution to copy the prototype?

var pool = new Pool(config)
var prototype = Object.assign(Reflect.getPrototypeOf(this), Reflect.getPrototypeOf(pool))
Reflect.setPrototypeOf(pool, prototype)
return pool

[charmander]

I don’t think it should be done with Object.assign. Would a workaround with a direct dependency on pg-pool be acceptable?

const Pool = require('pg-pool')
const {Client} = require('pg')

class MyPool extends Pool {
  constructor(options) {
    super({Client, ...options})
  }

  f() {
    console.log('...')
  }
}

[tulayang]

@charmander

pg-pool should be ok. But the ts definition for pg-pool is wrong. See https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/pg-pool/index.d.ts

That incorrectly refer to pg definition. Therefore, cannot use pg-pool like：

import * as Pool from 'pg-pool'  // error
import Pool from 'pg-pool'       // error

import {Pool} from 'pg-pool'     

console.log(Pool)                // error, not found Pool

[charmander]

pg’s bound pool (the Pool export) is a class as of 8.0.