Change 522221 had a related patch set uploaded (by Krinkle; owner: Krinkle):
[mediawiki/core@master] resourceloader: Remove use of object registering in test suites

https://gerrit.wikimedia.org/r/522221

Change 522222 had a related patch set uploaded (by Krinkle; owner: Krinkle):
[mediawiki/core@master] resourceloader: Remove support for 'object' in wgResourceModules

https://gerrit.wikimedia.org/r/522222

Change 522221 merged by jenkins-bot:
[mediawiki/core@master] resourceloader: Remove use of object registering in test suites

https://gerrit.wikimedia.org/r/522221

Change 522518 had a related patch set uploaded (by Krinkle; owner: Krinkle):
[mediawiki/core@master] resourceloader: Remove register() 'object' use in OutputPageTest

https://gerrit.wikimedia.org/r/522518

Change 522518 merged by jenkins-bot:
[mediawiki/core@master] resourceloader: Remove register() 'object' use in OutputPageTest

https://gerrit.wikimedia.org/r/522518

Change 522222 merged by jenkins-bot:
[mediawiki/core@master] resourceloader: Remove support for 'object' in wgResourceModules

https://gerrit.wikimedia.org/r/522222

Yay: https://travis-ci.org/cmln/chameleon/jobs/559626849

Could you provide information on where/when this was deprecated?

@Foxtrott It's been a discouraged feature since 2011 really, obsolete with other ways of registering. It was never used in production for MediaWiki core, tarballed, or WMF-deployed projects.

Release notes for 1.34 (not yet released), are at source.

For migrate, you can either: return the object from a factory closure:

// before
register(name, $obj);
// after
register(name, ['factory' => function () use ($obj) {
  return $obj;
});

Or, if the object is a plain construction, I'd recommend the declarative format, like so:

// before
register(name, new MyClass([
  'x' => 'y'
]);
// after
register(name, [
  'class' => MyClass::class,
  'x' => 'y'
]);

So, not deprecated and you don't care.

It was never intended for use, there were no known uses in any past or present released version of MediaWiki core, WMF production repos, and no current uses anywhere in repositories hosted on Gerrit, and no usage anywhere as found through Codesearch for third-party hosted repositories on GitHub etc.. Per these search queries I did:

• usage of "object" key
• usage of raw instance

With no known usage, and only a small chance of some other patterns I couldn't match or in private/other repos, I decided it would not be worth the overhead and maintenance cost of 6 more months of WMF-funded development resources. And thus to remove without deprecation. This is in line with our Deprecation policy – (I will e-mail Wikitech-l this week as well. I should have done this last week.)