Before I forget again, a somehow similar messageid operator exists to search by message key (without language subpage), e.g. https://translatewiki.net/w/i.php?title=Special%3ASearchTranslations&query=messageid%3A%22MediaWiki%3ATitlematches%22 (first revealed by Nikerabbit in https://gerrit.wikimedia.org/r/#/c/94064/2/includes/specials/SpecialAllmessages.php).

[offtopic] Just in case someone else likes it, I use this a script like this to easily get from a WMF wiki to Translatewiki:

// Add a link to Translatewiki above the interface messages
if ( 8 === mw.config.get( 'wgNamespaceNumber' ) ) {
	mw.util.addPortletLink(
		'p-namespaces',
		'//translatewiki.net/wiki/' +
			mw.util.wikiUrlencode( mw.config.get( 'wgPageName' ) ) +
			'/' + mw.config.get( 'wgUserLanguage' ),
		'Translatewiki',
		'ca-trans',
		'See this message on Translatewiki.net'
	);
}

I'd like to discuss expected behaviour here. We have Special:Translations for a list of all translations of a key. For example https://translatewiki.net/wiki/Special:Translations/MediaWiki:Show.

You could search for "MediaWiki:Show" on the main page, or for "Show".

1. What would be expected behaviour, and
2. What would the algorithm look like that makes the decision?

Suggestion: I think the easier way would be a two click work flow. Similar to a "Did you mean". We can have Special:SearchTranslations do a check for keys that match the search term, and if it finds something, we could add a link to Special:Translations/<key> at the top of the search results.

How does that sound?

(In reply to Siebrand Mazeland from comment #3)

How does that sound?

It sounds like a separate feature requests, unless Nnemo disagrees on my interpretation of his request. The "go" search feature only checks title match; optionally you could pick an appropriate langcode subpage.

I think that @Nemo_bis has understood my request correctly. You may see the edited link to the discussion in the task's description.

Change 196140 had a related patch set uploaded (by Phoenix303):
Search message with message key without interwiki prefix

https://gerrit.wikimedia.org/r/196140

Change 226335 had a related patch set uploaded (by Phoenix303):
Search with exact title match

https://gerrit.wikimedia.org/r/226335

Change 226335 merged by jenkins-bot:
Search with exact title match

https://gerrit.wikimedia.org/r/226335

The "go" search feature only checks title match; optionally you could pick an appropriate langcode subpage.

More: that's definitely T70518: Special:SearchTranslations: allow messageid with ElasticSearch (we already take care of language scoring etc. there). This is for Special:Search-like "go" title match, while that's for the generic message key search.

Change 196140 abandoned by Nikerabbit:
Search message with message key

Reason:
Does not rebase cleanly, and I think we can resolve our use cases in other ways.

https://gerrit.wikimedia.org/r/196140

Change 236403 had a related patch set uploaded (by Phoenix303):
Ignore language parameter in the query when url parameter 'language' is present.

https://gerrit.wikimedia.org/r/236403

Change 236403 merged by jenkins-bot:
Ignore the language query parameter when a title with language subpage is given.

https://gerrit.wikimedia.org/r/236403