Closing in favor of T427642.

See https://stackoverflow.com/questions/4538732/what-does-collation-mean

What's a collation?

Nice idea ‚ worth noting that category refs can be inside templates/parser functions, so plain text replacement won't always work. Pywikibot's category.py move already does something similar.

This is already possible with the deepcategory search operator. That's a hacky way and often does not work; it doesn't solve this issue but so far it wasn't mentioned here. Further info on missing things and available ways & tools here.

Change #1258362 abandoned by Saucy:

[mediawiki/core@master] CategoryViewer: Change access modifiers

https://gerrit.wikimedia.org/r/1258362

Places in core needing migration:

• WikiFilePage::getForeignCategories()

If your implementation doesn't care about what sounds like 80 to 90% of the original class' implementation, why do we need to make these irrelevant parts public to subclasses?

The reason for reusing the methods is that I have no reason to make the paging links, count message, etc., any different from what is generated by MediaWiki core. In fact, I want those components to be exactly the same as in vanilla MediaWiki.

In T422579#11797860, @thiemowmde wrote:

I do have a few questions:

• The current PictoCategoryViewer class doesn't look complicated. How would that benefit from being able to reuse code from core's CategoryViewer class?
• The patch https://gerrit.wikimedia.org/r/1258362 exposes 4 methods. Neither looks complicated, in my opinion. What is the benefit of reusing them rather than making your own custom version? Doing so gives you the chance to customize the code exactly to your needs without the need to add extra complexity to the base class.
• Why does https://gerrit.wikimedia.org/r/1258362 expose 2 previously private properties?
• The LanguageConverter should be changed to dependency injection via a constructor parameter.
• Generally it sounds more like what you need is a hook that allows you to modify the presentation of each page link. Isn't that what the CategoryViewer::generateLink hook already does? Maybe it's just missing something and your problem can be solved by adding one or two new parameters to the hook?

I do have a few questions:

• The current PictoCategoryViewer class doesn't look complicated. How would that benefit from being able to reuse code from core's CategoryViewer class?
• The patch https://gerrit.wikimedia.org/r/1258362 exposes 4 methods. Neither looks complicated, in my opinion. What is the benefit of reusing them rather than making your own custom version? Doing so gives you the chance to customize the code exactly to your needs without the need to add extra complexity to the base class.
• Why does https://gerrit.wikimedia.org/r/1258362 expose 2 previously private properties?
• The LanguageConverter should be changed to dependency injection via a constructor parameter.
• Generally it sounds more like what you need is a hook that allows you to modify the presentation of each page link. Isn't that what the CategoryViewer::generateLink hook already does? Maybe it's just missing something and your problem can be solved by adding one or two new parameters to the hook?

Change #1258362 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Saucy):

[mediawiki/core@master] CategoryViewer: Change access modifiers

https://gerrit.wikimedia.org/r/1258362

Change #575398 restored by Thcipriani:

[mediawiki/core@master] Api: Populate variables startsortkey and endsortkey before conditional check

https://gerrit.wikimedia.org/r/575398

Change #189178 restored by Thcipriani:

[mediawiki/core@master] Add per-category editnotices

https://gerrit.wikimedia.org/r/189178

Change #65176 restored by Thcipriani:

[mediawiki/core@master] Automatically move category members when redirected

https://gerrit.wikimedia.org/r/65176

Change #789968 restored by Thcipriani:

[mediawiki/core@master] CategoryViewer: Display count link if from/until parameter is set

https://gerrit.wikimedia.org/r/789968

Change #887962 restored by Thcipriani:

[mediawiki/core@master] LanguageConverter: Keep the namespace unchanged for findVariantLink()

https://gerrit.wikimedia.org/r/887962

Change #327762 restored by Thcipriani:

[mediawiki/core@master] Make language-appropriate collations default during install

https://gerrit.wikimedia.org/r/327762

Change #533728 restored by Thcipriani:

[mediawiki/core@master] Better randomness for Special:RandomInCat and no more subcats

https://gerrit.wikimedia.org/r/533728