I don't think it's feature is completely broken, as it worked on an untranslated page - https://www.mediawiki.org/w/index.php?title=User%3AReedy%2FTest&diff=6041122&oldid=566646

Either way, it shouldn't be failing silently and doing apparently nothing...

Trying another page https://www.mediawiki.org/wiki/Help:Categories/Test it seems there is again weirdness in the diff...

And on Publish,

{
	"error": {
		"code": "pt-shake-empty",
		"info": "Empty translation unit for marker \"3\".",
		"*": "See https://www.mediawiki.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/postorius/lists/mediawiki-api-announce.lists.wikimedia.org/> for notice of API deprecations and breaking changes."
	},
	"servedby": "mw-api-ext.eqiad.main-5cf9879585-tlrxx"
}

Which is seemingly suppressed by the frontend JS. Nothing is shown at all.

It seems it does some weird duplication of syntax etc too. Which really becomes T342651: Special:PagePreparation should handled pages with translation markup better (or do nothing).

I think the TLDR for handling is using .fail() etc

Change 944244 had a related patch set uploaded (by Reedy; author: Reedy):

[mediawiki/extensions/Translate@master] WIP: PagePreparation: Add fail() handlers to api calls

https://gerrit.wikimedia.org/r/944244

Change 944244 merged by jenkins-bot:

[mediawiki/extensions/Translate@master] PagePreparation: Add/Improve error handling

https://gerrit.wikimedia.org/r/944244

@abi_ Please attach F38101348 (see https://www.mediawiki.org/wiki/Phabricator/Help#File_visibility).

In T342628#9235054, @Tacsipacsi wrote:

@abi_ Please attach F38101348 (see https://www.mediawiki.org/wiki/Phabricator/Help#File_visibility).

Thanks, fixed.

Yay!

I'm sure there's always more we can do, but we're catching some (most?) of the errors that were annoying me at the time.

Can always file tasks down the line if/when I or anyone else finds any issues :)