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Maniphest T410363

Apply translation does not work: Cannot read properties of undefined (reading 'getTitleForLanguage')
Closed, ResolvedPublic4 Estimated Story PointsBUG REPORT
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Assigned To
ngkountas
Authored By
abi_
Nov 18 2025, 8:57 AM
Project Tags
Referenced Files
F85877507: image.png
Jun 1 2026, 7:29 AM
F81082263: image.png
May 12 2026, 7:56 AM
F70815311: Screencast From 2025-12-02 10-54-36.webm
Dec 2 2025, 8:00 AM
F70271769: image.png
Nov 18 2025, 8:57 AM
Subscribers
abi_
Aklapper
ngkountas
Nikerabbit
• Wangombe

Description

Steps to replicate the issue (include links if applicable):

What happens?:
Translation does not load

image.png (1,511×888 px, 286 KB)

What should have happened instead?:
Translation should have been loaded and applied.

Software version (on Special:Version page; skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):
Noticed on Logstash:

Cannot read properties of undefined (reading 'getTitleForLanguage')
at https://it.wikipedia.org/w/load.php?lang=it&modules=ext.centralNotice.geoIP%7Cext.centralauth.ForeignApi%7Cext.centralauth.centralautologin.clearcookie%7Cext.checkUser.clientHints%7Cext.cx.articlefilters%2Cmodel%7Cext.cx.eventlogging.campaigns%7Cext.dismissableSiteNotice%2CeventLogging%2CnavigationTiming%2Cpopups%2CwikimediaEvents%2CxLab%7Cext.echo.api%2Cinit%7Cext.eventLogging.metricsPlatform%7Cext.growthExperiments.HelpPanel.init%7Cext.growthExperiments.SuggestedEditSession%7Cext.uls.common%2Ccompactlinks%2Cinterface%2Cpreferences%2Cwebfonts%7Cext.urlShortener.toolbar%7Cext.wikimediaEvents.xLab%7Cjquery%2Coojs%2Csite%2Cvue%2Cvuex%7Cjquery.client%2CtextSelection%7Cjquery.uls.data%7Cmediawiki.ForeignApi%2CString%2CTitle%2Capi%2Cbase%2Ccldr%2Ccookie%2Cexperiments%2CjqueryMsg%2Clanguage%2Cstorage%2Cuser%2Cutil%2CvisibleTimeout%7Cmediawiki.ForeignApi.core%7Cmediawiki.editfont.styles%7Cmediawiki.libs.pluralruleparser%7Cmediawiki.page.ready%7Cmw.cx.SiteMapper%2Ceventlogging%2Cutil%7Cmw.cx3&skin=contenttranslation&version=1nq9x:841:596

Source: https://logstash.wikimedia.org/app/discover#/doc/logstash-*/logstash-default-1-7.0.0-1-2025.11.18?id=8HcmlpoB9tkJMVA5owSw

  • 28 November, 2025 - 264 occurences in the last 10 days - 2nd most frequent error.

Details

Related Changes in Gerrit:
SubjectAuthorRepoBranchLines +/-
CX3 Build 1.0.0+20260512Nik Gkountasmediawiki/extensions/ContentTranslationmaster+2 K -2 K
CX: Add logging for language links fetching/storage.Wangombemediawiki/extensions/ContentTranslationmaster+152 -24
Disable article language selector if no language-title groupNik Gkountasmediawiki/extensions/ContentTranslationmaster+7 -1
useSuggestionLoad: Throw error if no page stored after metadata fetchingNik Gkountasmediawiki/extensions/ContentTranslationmaster+8 -5
fetchLanguageTitles API: reject promise on fetch failureNik Gkountasmediawiki/extensions/ContentTranslationmaster+30 -16
Customize query in gerrit

Related Objects

Event Timeline

abi_ created this task.Nov 18 2025, 8:57 AM
Restricted Application added a subscriber: Aklapper. · View Herald TranscriptNov 18 2025, 8:57 AM
abi_ triaged this task as Medium priority.Nov 18 2025, 8:57 AM
abi_ moved this task from Backlog to Ready for dev on the LPL Essential (FY2025-26 Q2) board.
abi_ set the point value for this task to 2.
abi_ added a project: ContentTranslation.Nov 18 2025, 9:16 AM
Nikerabbit added a project: LPL Projects (CX observability).Nov 19 2025, 8:03 AM
• Wangombe changed the task status from Open to In Progress.Nov 25 2025, 9:11 AM
• Wangombe claimed this task.
• Wangombe moved this task from Ready for dev to In Progress on the LPL Essential (FY2025-26 Q2) board.
Nikerabbit moved this task from Needs Triage to Translation editor on the ContentTranslation board.Nov 27 2025, 8:18 AM
abi_ updated the task description. (Show Details)Nov 28 2025, 7:35 AM
• Wangombe added a comment.Dec 2 2025, 8:00 AM

Is it possible to provide more information about this bug? I tried replicating this with Google and MinT. None produced the results in the ticket description.

Nikerabbit subscribed.Dec 10 2025, 12:05 PM
In T410363#11422643, @Wangombe wrote:

Is it possible to provide more information about this bug? I tried replicating this with Google and MinT. None produced the results in the ticket description.

Figuring out the cause is part of the task. This needs debugging. Looking for clues in Logstash, reading the code and generating hypothesis how it may fail, possibly adding more logging to learn more, etc.

Nikerabbit edited projects, added: LPL Essential (FY2025-26 Q3&4); removed: LPL Essential (FY2025-26 Q2).Jan 15 2026, 4:09 PM
Nikerabbit moved this task from Backlog to In Progress on the LPL Essential (FY2025-26 Q3&4) board.
gerritbot added a comment.Jan 19 2026, 1:29 PM

Change #1228492 had a related patch set uploaded (by Wangombe; author: Wangombe):

[mediawiki/extensions/ContentTranslation@master] CX: Add a null check to getTitleForLanguage

https://gerrit.wikimedia.org/r/1228492

gerritbot added a project: Patch-For-Review.Jan 19 2026, 1:29 PM
ngkountas subscribed.Jan 22 2026, 4:44 PM

The error still occurs (121 occurrences last week).

The root cause of the issue is that the language links for the currently selected article could not be fetched/stored successfully. Adding null checks to the current point of failure, will just close this task and open a new one.

My suggestion is that we need to improve the error handling for the failed API requests, especially for data that are crucial for the application. Until then, we can keep this task open and maybe lower its priority for now.

Nikerabbit edited projects, added: LPL Projects (Other); removed: LPL Projects (CX observability).Feb 16 2026, 12:38 PM
Nikerabbit added a comment.Mar 4 2026, 8:09 AM

Code reviews in progress.

• Wangombe removed • Wangombe as the assignee of this task.Apr 13 2026, 7:46 AM
• Wangombe subscribed.
ngkountas mentioned this in T424154: Mobile translation editor: Error when trying to edit translation for pages not connected to Wikidata.Apr 22 2026, 6:17 PM
gerritbot added a comment.Apr 23 2026, 12:02 AM

Change #1276442 had a related patch set uploaded (by Nik Gkountas; author: Nik Gkountas):

[mediawiki/extensions/ContentTranslation@master] fetchLanguageTitles API: reject promise on fetch failure

https://gerrit.wikimedia.org/r/1276442

gerritbot added a comment.Apr 23 2026, 12:02 AM

Change #1276443 had a related patch set uploaded (by Nik Gkountas; author: Nik Gkountas):

[mediawiki/extensions/ContentTranslation@master] Disable article language selector if no language-title group

https://gerrit.wikimedia.org/r/1276443

gerritbot added a comment.Apr 23 2026, 12:02 AM

Change #1276445 had a related patch set uploaded (by Nik Gkountas; author: Nik Gkountas):

[mediawiki/extensions/ContentTranslation@master] useSuggestionLoad: Throw error if no page stored after metadata fetching

https://gerrit.wikimedia.org/r/1276445

gerritbot added a comment.Apr 28 2026, 12:41 PM

Change #1276442 merged by jenkins-bot:

[mediawiki/extensions/ContentTranslation@master] fetchLanguageTitles API: reject promise on fetch failure

https://gerrit.wikimedia.org/r/1276442

ReleaseTaggerBot added a project: MW-1.47-notes (1.47.0-wmf.1; 2026-05-05).Apr 28 2026, 1:00 PM
gerritbot added a comment.Apr 29 2026, 6:09 AM

Change #1276445 merged by jenkins-bot:

[mediawiki/extensions/ContentTranslation@master] useSuggestionLoad: Throw error if no page stored after metadata fetching

https://gerrit.wikimedia.org/r/1276445

gerritbot added a comment.Apr 29 2026, 10:26 AM

Change #1276443 merged by jenkins-bot:

[mediawiki/extensions/ContentTranslation@master] Disable article language selector if no language-title group

https://gerrit.wikimedia.org/r/1276443

Nikerabbit assigned this task to ngkountas.Apr 30 2026, 6:50 AM
Nikerabbit moved this task from In Progress to Pending Deployment on the LPL Essential (FY2025-26 Q3&4) board.
Nikerabbit removed a project: Patch-For-Review.
gerritbot added a comment.Apr 30 2026, 6:51 AM

Change #1228492 abandoned by Nikerabbit:

[mediawiki/extensions/ContentTranslation@master] CX: Add logging for language links fetching/storage.

https://gerrit.wikimedia.org/r/1228492

Nikerabbit moved this task from Pending Deployment to In Progress on the LPL Essential (FY2025-26 Q3&4) board.May 12 2026, 7:56 AM

I do not see change in error frequency after these patches:

image.png (1,911×968 px, 125 KB)

Nikerabbit moved this task from In Progress to Pending Deployment on the LPL Essential (FY2025-26 Q3&4) board.May 12 2026, 10:56 AM

Changes are not in effect yet, because there hasn't been a CX build.

gerritbot added a comment.May 12 2026, 2:18 PM

Change #1286377 had a related patch set uploaded (by Nik Gkountas; author: Nik Gkountas):

[mediawiki/extensions/ContentTranslation@master] CX3 Build 1.0.0+20260512

https://gerrit.wikimedia.org/r/1286377

gerritbot added a project: Patch-For-Review.May 12 2026, 2:18 PM
gerritbot added a comment.May 14 2026, 12:22 AM

Change #1286377 merged by jenkins-bot:

[mediawiki/extensions/ContentTranslation@master] CX3 Build 1.0.0+20260512

https://gerrit.wikimedia.org/r/1286377

Maintenance_bot removed a project: Patch-For-Review.May 14 2026, 12:31 AM
Nikerabbit moved this task from Pending Deployment to Need QA on the LPL Essential (FY2025-26 Q3&4) board.May 21 2026, 11:37 AM

There is already one event in wmf.3 https://logstash.wikimedia.org/app/discover#/doc/logstash-*/logstash-default-1-7.0.0-1-2026.05.21?id=UHHiSZ4Br2RT0BE3ypIc which indicates this is not fully fixed. Can check next week is there is any change in volume to indicate there is another cause.

Nikerabbit closed this task as Resolved.Jun 1 2026, 7:29 AM
Nikerabbit mentioned this in T427756: Cannot read properties of undefined (reading 'getTitleForLanguage') at getCurrentTitleByLanguage.
Nikerabbit changed the point value for this task from 2 to 4.
Nikerabbit moved this task from Need QA to Done on the LPL Essential (FY2025-26 Q3&4) board.

image.png (1,903×541 px, 79 KB)

I am fairly sure we have fixed on cause of this. For the other one, I have created T427756: Cannot read properties of undefined (reading 'getTitleForLanguage') at getCurrentTitleByLanguage.

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