Use class-extends to wrap Pool (#1541)

* Use class-extends to wrap Pool

* Minimize diff

* Test `BoundPool` inheritance

Co-authored-by: Charmander <~@charmander.me>
Co-authored-by: Brian C <brian.m.carlson@gmail.com>

packages/pg/lib/index.js

@@ -7,25 +7,18 @@
  * README.md file in the root directory of this source tree.
  */
 
-var util = require('util')
 var Client = require('./client')
 var defaults = require('./defaults')
 var Connection = require('./connection')
 var Pool = require('pg-pool')
-const checkConstructor = require('./compat/check-constructor')
 
 const poolFactory = (Client) => {
-  var BoundPool = function (options) {
-    // eslint-disable-next-line no-eval
-    checkConstructor('pg.Pool', 'PG-POOL-NEW', () => eval('new.target'))
-
-    var config = Object.assign({ Client: Client }, options)
-    return new Pool(config)
+  return class BoundPool extends Pool {
+    constructor (options) {
+      var config = Object.assign({ Client: Client }, options)
+      super(config)
+    }
   }
-
-  util.inherits(BoundPool, Pool)
-
-  return BoundPool
 }
 
 var PG = function (clientConstructor) {

packages/pg/test/integration/gh-issues/1542-tests.js

@@ -0,0 +1,25 @@
+
+"use strict"
+const helper = require('./../test-helper')
+const assert = require('assert')
+
+const suite = new helper.Suite()
+
+suite.testAsync('BoundPool can be subclassed', async () => {
+  const Pool = helper.pg.Pool;
+  class SubPool extends Pool {
+
+  }
+  const subPool = new SubPool()
+  const client = await subPool.connect()
+  client.release()
+  await subPool.end()
+  assert(subPool instanceof helper.pg.Pool)
+})
+
+suite.test('calling pg.Pool without new throws', () => {
+  const Pool = helper.pg.Pool;
+  assert.throws(() => {
+    const pool = Pool()
+  })
+})