Broken IndexedDB event typings in 3.1.5

[dpogue]

TypeScript Version: 3.1.5

Search Terms:
indexedDB

Code

let dbreq = indexedDB.open('test', 1);

dbreq.onsuccess = function (evt) {
    let database = evt.target.result;
}

Expected behavior:
evt.target.result should be an IDBDatabase

Actual behavior:
TS2339: Property 'result' does not exist on type 'EventTarget'.

Playground Link:
http://www.typescriptlang.org/play/index.html#src=let%20dbreq%20%3D%20indexedDB.open('test'%2C%201)%3B%0D%0A%0D%0Adbreq.onsuccess%20%3D%20function%20(evt)%20%7B%0D%0A%20%20%20%20let%20database%20%3D%20evt.target.result%3B%0D%0A%7D

Related Issues:
This is caused by the updates resulting from #25547

It works if you add a cast:

let dbreq = indexedDB.open('test', 1);

dbreq.onsuccess = function (evt) {
    let database = (evt.target as IDBOpenDBRequest).result;
}

[weswigham]

PRs welcomed. You can find more information about contributing lib.d.ts fixes at https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md#contributing-libdts-fixes.

[sandersn]

Following on to @weswigham’s comment, this is now easily fixed as an extension to microsoft/TypeScript-DOM-lib-generator#707; ProgressEvent now has a type parameter that controls the type of target, so it’s just a matter of passing the type in from the subclass declaration.

[tonitrnel]

It can be write like this

let dbreq = indexedDB.open('test', 1);

dbreq.onsuccess = function (evt) {
  let database = dbreq.result;
}