[Taking the bug; it does not depend on 50007.]

I'm gonna go with no. 114 for the namespace and 115 for the corresponding talk page namespace; will submit it under its English name and add an alias in Ukrainian.

Why not adding it with the Ukrainian name and setting its English name as the canonical one as requested?

How about you submit a patch if you know how to do that?

No, sorry, I can't (at least for the time being). But let me say it again that it is important to do it with the English canonical namespace instead of dealing with aliases. While it might seem the same for a regular user, it can cause problems for script maintainers while porting scripts across wikis. Thanks

Well, then perhaps you can tell me how do I set up a canonical name for a non–system namespace so that I can update some documentation on MediaWiki.org and learn something new today!

PS That's totally serious—I don't think you can define a canonical name for a custom namespace.

Tomasz, when I come here, I expect to have serious collaboration, not playing fool or whatever. If setting canonical namespace is not possible for custom namespaces, just mention it in the very first comment to make it clear. It is not straightforward for me, as I can see canonical English names for custom Index, Page and Module namespaces for Ukrainian Wikisource:

https://uk.wikisource.org/w/api.php?action=query&meta=siteinfo&siprop=general|namespaces|namespacealiases

But if you still insist that it is not possible, it is fine for me and I will probably submit a new request for changes in the Mediawiki core in order to make it possible.

Assuming good faith as always, are you?

The "Index" and "Page" namespaces are added by an extension (ProofreadPage), and the Module namespace is added by the Scribunto extension, so that's why you can set a canonical name for them.

I have no idea what's the correct way to follow your request with, but I seriously doubt it's adding a new namespace to MediaWiki core.

[Un–assigning and un-CC'ing myself from this bug. Good luck.]

I didn't mean adding a new namespace to the Mediawiki core, but rather adding possibility of adding canonical names for custom namespaces.

(In reply to comment #8)

I didn't mean adding a new namespace to the Mediawiki core, but rather adding
possibility of adding canonical names for custom namespaces.

I suggest you to write what you want to achieve rather than the supposed ways to achieve it. The misunderstanding here probably is that you want a namespace alias but you're calling it canonical because canonical names redirect too.

I wrote what I want in the very first comment. And no, I don't confuse aliases with canonical names. I would like to be able to have the same value for wgCanonicalNamespace in Javascript regardless of the language of wiki.

http://www.mediawiki.org/wiki/Manual:Interface/JavaScript#Page-specific

Change 72054 had a related patch set uploaded by Odder:
A partial fix for https://bugzilla.wikimedia.org/show_bug.cgi?id=50561

https://gerrit.wikimedia.org/r/72054

[Assigning to Dmytro since it's his patch, removing dependency.]

Change 72054 merged by jenkins-bot:
(bug 50561) Add 'Translation' namespace for ukwikisource

https://gerrit.wikimedia.org/r/72054