Bug 247613

WPT: https://wpt.live/IndexedDB/idbindex_keyPath.any.html

Steps to reproduce:

const store = db.createObjectStore("store")
store.createIndex("byIdArrayKey", ["id"], { multiEntry: false }))

store.put({
  id: 1,
  title: "hello"
})

Expected behavior:
The index key that gets extracted from the record value should be [1] (array with a single subkey)

Actual results:
On WebKit this yield a scalar key with value 1 (number)
Confirmed on Safari 16 on macOS and iOS and Safari Tech Preview Release 156 (Safari 16.4, WebKit 17615.1.8.5)

An array keyPath should always produce an array key (https://www.w3.org/TR/IndexedDB/#evaluate-a-key-path-on-a-value)

Works as expected on V8 and SpiderMonkey
Note: single entry array keyPaths work as expected with IDBObjectStore on WebKit. The unexpected behavior is only observed with IDBIndex keyPaths.