IDBFactory.deleteDatabase(): result is undefined, not null

[RizgarOzan]

Description

Fixes the result value documented on the IDBFactory.deleteDatabase() page:

• The "Return value" section said the request's result is null after a successful deletion. It is undefined. The page's own "Description" section already says undefined, so the page contradicted itself.
• The example logged event.result. The success event here is an IDBVersionChangeEvent, which has no result property, so the line printed undefined for the wrong reason. It now logs dbDeleteRequest.result.

Motivation

The spec sets the result to undefined. IndexedDB 3.0, §4.3 The IDBFactory interface, deleteDatabase(name) steps:

Otherwise, set request's result to undefined, set request's done flag to true, and fire a version change event named success at request with result and null.

All three engines do the same:

• Blink: measured, see below.
• WebKit: IDBOpenDBRequest::onDeleteDatabaseSuccess() calls setResultToUndefined() (Source/WebCore/Modules/indexeddb/IDBOpenDBRequest.cpp).
• Gecko: BackgroundFactoryRequestChild::HandleResponse(const DeleteDatabaseRequestResponse&) passes JS::UndefinedHandleValue as the result (dom/indexedDB/ActorsChild.cpp).

How I tested

I wrote a test page that opens a database (version 3), closes it, deletes it, and then deletes a database that doesn't exist. In each success handler it logs the request's result. Output in Edge 153 (Chromium, headless):

existing db: event type = success
existing db: event constructor = IDBVersionChangeEvent
existing db: request.result = undefined (typeof undefined)
existing db: event.target.result = undefined (typeof undefined)
existing db: 'result' in event = false
existing db: event.oldVersion = 3, event.newVersion = null
missing db: request.result = undefined (typeof undefined)
missing db: event.oldVersion = 0, event.newVersion = null

markdownlint-cli2, prettier --check, and cspell (with .vscode/cspell.json) all pass on the changed file.

Related issues and pull requests

The page's other gaps (the blocked state) were covered in #44350 for #42779.

[github-actions]

Preview URLs (1 page)

• /en-US/docs/Web/API/IDBFactory/deleteDatabase

[wbamberg]

Interesting, it looks like the non-normative bit of the spec is wrong:

Attempts to delete the named database. If the database already exists and there are open connections that don’t close in response to a versionchange event, the request will be blocked until they all close. If the request is successful request’s result will be null.

[wbamberg]

👍 thank you!

[RizgarOzan]

Yes, that sentence is from the "For web developers" box (<div class="domintro note"> in the source), which is non-normative. The method steps themselves say "set request's result to undefined" and have since w3c/IndexedDB#202 (2017), and engines follow the steps. I filed w3c/IndexedDB#507 to get the note fixed.