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Maniphest T429887

Talk page: edit section: Cannot find section -> off by one error
Closed, ResolvedPublicBUG REPORT
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Description

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

What happens?:

Cannot find section
You tried to edit a section that does not exist. It may have been moved or deleted while you were viewing the page.

What should have happened instead?:

Editing Dyskusja wikipedysty:Saper (section)

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

MediaWiki 1.47.0-wmf.7 (rMW294e7850569f) 2026-06-23T00:03:20

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

Section number 529 linked from the edit source does not exist

https://pl.wikipedia.org/w/index.php?title=Dyskusja_wikipedysty:Saper&action=edit&section=529

Section number 528 works

https://pl.wikipedia.org/w/index.php?title=Dyskusja_wikipedysty:Saper&action=edit&section=528

Details

Related Changes in Gerrit:
SubjectAuthorRepoBranchLines +/-
Bump wikimedia/parsoid to 0.24.0-a13Isabelle Hurbain-Palatinmediawiki/vendormaster+2 K -2 K
Unbalanced preproc prevents headingArlolramediawiki/services/parsoidmaster+1 K -1 K
Customize query in gerrit

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Event Timeline

saper created this task.Jun 23 2026, 9:38 AM
Restricted Application added a subscriber: Aklapper. · View Herald TranscriptJun 23 2026, 9:38 AM
Aklapper added a project: MediaWiki-Page-editing.Jun 23 2026, 9:43 AM
MichalSobkowski subscribed.Jun 23 2026, 10:23 AM
Zaidusyy claimed this task.Jun 23 2026, 11:03 AM
Zaidusyy subscribed.

Hi! I was able to reproduce this issue and would like to investigate it.

matmarex edited projects, added: Parsoid; removed: MediaWiki-Page-editing.Jun 23 2026, 12:31 PM
matmarex subscribed.

Looks like a Parsoid bug. https://pl.wikipedia.org/w/index.php?title=Dyskusja_wikipedysty:Saper&useparsoid=0#toolserwer_3 has the correct, working link.

The first broken section on the page is https://pl.wikipedia.org/w/index.php?title=Dyskusja_wikipedysty:Saper&useparsoid=1#Odp:[[Akceleracja_(biologia), probably due to the unclosed [[ markup.
When using the old parser, that section has no [edit] link: https://pl.wikipedia.org/w/index.php?title=Dyskusja_wikipedysty:Saper&useparsoid=0#Odp:[[Akceleracja_(biologia).
When using Parsoid, it has a link, and all section edit links from that point are off by one.

SomeRandomDeveloper subscribed.Jun 23 2026, 3:52 PM
ABreault-WMF added a parent task: T391624: Parsoid section edit link issues.Jun 24 2026, 12:13 AM
ABreault-WMF subscribed.
== Test [[123 ==

asdf
ssastry subscribed.Jun 25 2026, 9:32 PM

T372387: Wrong section numbering if Parsoid is used and wikitext is invalid is related which we previously resolved.

gerritbot added a comment.Jun 26 2026, 8:27 PM

Change #1305971 had a related patch set uploaded (by Arlolra; author: Arlolra):

[mediawiki/services/parsoid@master] Unbalanced preproc prevents heading

https://gerrit.wikimedia.org/r/1305971

gerritbot added a project: Patch-For-Review.Jun 26 2026, 8:27 PM
ABreault-WMF claimed this task.Jun 26 2026, 8:34 PM
ABreault-WMF added a project: Content-Platform-Team (Work In Progress).
In T429887#12044783, @Zaidusyy wrote:

Hi! I was able to reproduce this issue and would like to investigate it.

@Zaidusyy Sorry, I put up a patch for this already. T391624: Parsoid section edit link issues, that this falls under, is an active area of development and probably not the best place to be looking for bugs to tackle. Hopefully you didn't spend too much time investigating

ABreault-WMF triaged this task as Medium priority.Jun 26 2026, 8:34 PM
ABreault-WMF moved this task from Backlog to Code Review on the Content-Platform-Team (Work In Progress) board.
Zaidusyy added a comment.Jun 26 2026, 9:25 PM

@ABreault-WMF
No worries, it was a good learning experience.
Thanks for the heads up

gerritbot added a comment.Jun 27 2026, 5:27 AM

Change #1305971 merged by jenkins-bot:

[mediawiki/services/parsoid@master] Unbalanced preproc prevents heading

https://gerrit.wikimedia.org/r/1305971

Maintenance_bot removed a project: Patch-For-Review.Jun 27 2026, 5:31 AM
ABreault-WMF moved this task from Code Review to To Deploy on the Content-Platform-Team (Work In Progress) board.Jun 27 2026, 1:27 PM
gerritbot added a comment.Jun 29 2026, 9:46 AM

Change #1306186 had a related patch set uploaded (by Isabelle Hurbain-Palatin; author: Isabelle Hurbain-Palatin):

[mediawiki/vendor@master] Bump wikimedia/parsoid to 0.24.0-a13

https://gerrit.wikimedia.org/r/1306186

gerritbot added a project: Patch-For-Review.Jun 29 2026, 9:46 AM
gerritbot added a comment.Jun 29 2026, 1:43 PM

Change #1306186 merged by jenkins-bot:

[mediawiki/vendor@master] Bump wikimedia/parsoid to 0.24.0-a13

https://gerrit.wikimedia.org/r/1306186

Maintenance_bot removed a project: Patch-For-Review.Jun 29 2026, 2:32 PM
ABreault-WMF moved this task from To Deploy to To Verify on the Content-Platform-Team (Work In Progress) board.Jul 2 2026, 3:40 PM
ABreault-WMF closed this task as Resolved.Jul 2 2026, 3:55 PM

Post-deploy and purge, the #Odp:[[Akceleracja_(biologia) heading is still on the page but now the section edit link on both

https://pl.wikipedia.org/wiki/Dyskusja_wikipedysty:Saper?useparsoid=0#toolserwer_3
https://pl.wikipedia.org/wiki/Dyskusja_wikipedysty:Saper?useparsoid=1#toolserwer_3

point to https://pl.wikipedia.org/w/index.php?title=Dyskusja_wikipedysty:Saper&action=edit&section=528

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