Change #1225083 had a related patch set uploaded (by SarthakSingh2904; author: SarthakSingh2904):

[mediawiki/extensions/Translate@master] PageTranslation: Fix incorrect "removed priority languages" log

https://gerrit.wikimedia.org/r/1225083

Patch submitted to Gerrit: PageTranslation: Fix incorrect "removed priority languages" log

The previous code only treated the input as a string (comma or newline separated), causing array inputs to be interpreted as empty/null.
This resulted in a false positive log entry claiming that priority languages were removed when they were simply being re-submitted as-is.

From the commit message, it sounds like only an incorrect log entry was recorded.
However, is it possible that the priority languages were actually being set to empty at that point, rather than this being purely a logging issue?

If they were incorrectly cleared, I wonder whether there is a need to identify the affected cases and restore the priority languages that were unintentionally removed.
Could you clarify whether the underlying data was modified, or if this was strictly limited to the log output?

In T414254#11510030, @Shirayuki wrote:

However, is it possible that the priority languages were actually being set to empty at that point, rather than this being purely a logging issue?

I also fear this is what happened. Looking at https://www.mediawiki.org/w/index.php?title=Special:Log&page=Growth%2FPersonalized+first+day%2FNewcomer+homepage%2FMeasurement+and+experiment+plan, I see only priority language change entry – probably because the second time you marked the page for translation, there wasn’t anything to remove anymore.

If they were incorrectly cleared, I wonder whether there is a need to identify the affected cases and restore the priority languages that were unintentionally removed.

Translate’s database tables are not versioned (though maybe they should be), so the removed rows are gone; the only way I can think of to restore the data is looking at the preceding priority language change log entry, and approximate based on that. This may fall short when the page has been renamed in the meantime.

I’ve dug into this a bit more. Unfortunately, the analysis of @SarthakSingh2904 wasn’t correct. The real bug is that the submitted value is empty unless the language selector field has been touched. That is,

• If there are no priority languages, an empty string is submitted, as expected.
• If the translation admin changes the list after the form was loaded, they are saved as expected (see example log: I could easily add back the priority languages that @Minorax accidentally removed). This change can be anything: addition, removal, even adding and subsequently removing a language (which is a usable workaround until the bug is fixed, by the way).
• The bug manifests if the page already has priority languages, and the translation admin doesn’t change them. In this case, the <input> doesn’t get populated with the list of existing languages, and so an empty list gets submitted.

As I have already expected, this is a Regression from https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Translate/+/1211663 / T410267: Build a language selector component into MediaWiki core by @abi_.

Change #1225160 had a related patch set uploaded (by SarthakSingh2904; author: SarthakSingh2904):

[mediawiki/extensions/Translate@master] Translate: Initialize priority languages input on page load

https://gerrit.wikimedia.org/r/1225160

Change #1225083 abandoned by SarthakSingh2904:

[mediawiki/extensions/Translate@master] PageTranslation: Fix incorrect "removed priority languages" log

Reason:

I have created a fresh submission as per the recommendation of the Reviewer

https://gerrit.wikimedia.org/r/1225083

Change #1225160 merged by jenkins-bot:

[mediawiki/extensions/Translate@master] Translate: Initialize priority languages input on page load

https://gerrit.wikimedia.org/r/1225160

I think this should be in the scope of the current task.

I disagree. I'll file a separate task, but I am not sure if we have time to do it.