Incorrect typings lead to pool.destroy is not a function

[dancrumb]

I'm using version 3.9.7 of mysql2, running TypeScript 5.4.3

I'm importing this module with import mysql from "mysql2/promise";

When I create a Pool with mysql.createPool, I get my pool and am able to use it without any problems.

However, when I come to wrap things up, I call pool.destroy(). No complaints from TS, but when I run the code, I get:

<REDACTED>/db/stores/SqlStore.js:19
        pool.destroy();
             ^

TypeError: pool.destroy is not a function
    at SqlStore.shutdown (<REDACTED>/db/stores/SqlStore.js:19:14)
    at <REDACTED>/tools/migrate-to-mongo.mts:85:54
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

I took a look at promises.d.ts in the code base and I can see why there's no type error:

export interface Pool extends Connection {

Since destroy is a method in the Connection interface, it's also a method in the Pool interface.

I'm not sure if the bug is the assertion that Pool extends Connection or whether it's just that Pool only supports some methods of Connection.

[dancrumb]

I'm guessing that this is probably what's going on with #2465

[wellwelwel]

Thanks, @dancrumb 🙋🏻‍♂️

---

I'll keep some debugging to check later:

import mysql from 'mysql2';
// import mysql from 'mysql2/promise';

const pool = mysql.createPool({});

typeof pool.addListener === 'undefined' && console.log('addListener');
typeof pool.beginTransaction === 'undefined' && console.log('beginTransaction');
typeof pool.changeUser === 'undefined' && console.log('changeUser');
typeof pool.commit === 'undefined' && console.log('commit');
typeof pool.config === 'undefined' && console.log('config');
typeof pool.connect === 'undefined' && console.log('connect');
typeof pool.destroy === 'undefined' && console.log('destroy');
typeof pool.emit === 'undefined' && console.log('emit');
typeof pool.end === 'undefined' && console.log('end');
typeof pool.escape === 'undefined' && console.log('escape');
typeof pool.escapeId === 'undefined' && console.log('escapeId');
typeof pool.eventNames === 'undefined' && console.log('eventNames');
typeof pool.execute === 'undefined' && console.log('execute');
typeof pool.format === 'undefined' && console.log('format');
typeof pool.getConnection === 'undefined' && console.log('getConnection');
typeof pool.getMaxListeners === 'undefined' && console.log('getMaxListeners');
typeof pool.listenerCount === 'undefined' && console.log('listenerCount');
typeof pool.listeners === 'undefined' && console.log('listeners');
typeof pool.off === 'undefined' && console.log('off');
typeof pool.on === 'undefined' && console.log('on');
typeof pool.once === 'undefined' && console.log('once');
typeof pool.pause === 'undefined' && console.log('pause');
typeof pool.ping === 'undefined' && console.log('ping');
typeof pool.pool === 'undefined' && console.log('pool');
typeof pool.prepare === 'undefined' && console.log('prepare');
typeof pool.prependListener === 'undefined' && console.log('prependListener');
typeof pool.prependOnceListener === 'undefined' && console.log('prependOnceListener');
typeof pool.query === 'undefined' && console.log('query');
typeof pool.rawListeners === 'undefined' && console.log('rawListeners');
typeof pool.releaseConnection === 'undefined' && console.log('releaseConnection');
typeof pool.removeAllListeners === 'undefined' && console.log('removeAllListeners');
typeof pool.removeListener === 'undefined' && console.log('removeListener');
typeof pool.resume === 'undefined' && console.log('resume');
typeof pool.rollback === 'undefined' && console.log('rollback');
typeof pool.setMaxListeners === 'undefined' && console.log('setMaxListeners');
typeof pool.threadId === 'undefined' && console.log('threadId');
typeof pool.unprepare === 'undefined' && console.log('unprepare');
typeof pool.promise === 'undefined' && console.log('promise');

---

✅ = Properly typed (no typings for non-existent methods)
❌ = Incorrectly typed (probably) — Need to look into them

pool	mysql2	mysql2/promise
beginTransaction	✅	❌
changeUser	✅	❌
commit	✅	❌
config	✅	❌
connect	✅	❌
destroy	✅	❌
pause	✅	❌
ping	✅	❌
prepare	✅	❌
resume	✅	❌
rollback	✅	❌
threadId	✅	❌
unprepare	❌	❌

---

All cited methods are based in undefined type results, but have typings brought directly from the Connection interface.