Maniphest T419908

DiscussionTools duplicates the meta-data sub-header content when Previewing
Closed, ResolvedPublicBUG REPORT
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Authored By

	Quiddity
	Mar 12 2026, 9:23 PM

Description

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

Edit an existing section of a talkpage, e.g. the thread at https://en.wikipedia.org/wiki/Talk:Example
Click "Preview"

What happens?:

The meta-data is duplicated. (Confirmed on Enwiki and Frwiki, with a default-setting account)

Details

Related Changes in Gerrit:

Subject	Repo	Branch	Lines +/-
Ensure preview parser matches the user's current read views parser	mediawiki/extensions/VisualEditor	master	+1 -0
Fix double post-processing in legacy preview case	mediawiki/extensions/DiscussionTools	wmf/1.46.0-wmf.19	+9 -1
Fix double post-processing in legacy preview case	mediawiki/extensions/DiscussionTools	master	+9 -1

Customize query in gerrit

Related Objects

Mentioned In: T419830: Signatures aren't properly recognized on ruwiktionary and other projects when using Parsoid, resulting in a missing [ reply ] button

Event Timeline

Quiddity created this task.Mar 12 2026, 9:23 PM

Restricted Application added a subscriber: Aklapper. · View Herald TranscriptMar 12 2026, 9:23 PM

matmarex added a subscriber: cscott.Mar 13 2026, 6:43 AM

Johannnes89 subscribed.Mar 13 2026, 9:04 AM

Happens in the 2017 editor's preview as well, which takes a different path.

It's caused by https://gerrit.wikimedia.org/r/c/mediawiki/extensions/DiscussionTools/+/1225002

I wonder if Don't invoke ParserAfterTidy hook from Parsoid extension handling (1251133) · Gerrit Code Review fixes that?

@cscott It doesn't seem to for me.

I looked into this, and it's the same cause as 1251133 though, except ::useParsoid() doesn't seem to be set when VE is doing the preview parse (for some reason). We could use another indication of a being a "parsoid parse" to avoid the issue, or fix VE to set ::useParsoid() when doing its preview parse.

I don't have a patch yet, but will figure one out on Monday if @ihurbain doesn't beat me to it.

Alternatively/additionally, the bug goes away if you set $wgUsePostprocCacheLegacy = true, which it should be in production shortly, since DT won't use the postprocessing cache otherwise.

Toadette subscribed.Sat, Mar 14, 4:34 PM

Change #1253446 had a related patch set uploaded (by Isabelle Hurbain-Palatin; author: Isabelle Hurbain-Palatin):

[mediawiki/extensions/DiscussionTools@master] Fix double post-processing in legacy preview case

https://gerrit.wikimedia.org/r/1253446

gerritbot added a project: Patch-For-Review.Mon, Mar 16, 11:11 AM

ihurbain claimed this task.Mon, Mar 16, 11:11 AM

ihurbain edited projects, added Content-Transform-Team (Work In Progress); removed Content-Transform-Team.

ihurbain removed a project: Parsoid.

ihurbain moved this task from Backlog to Code Review on the Content-Transform-Team (Work In Progress) board.

Change #1253551 had a related patch set uploaded (by C. Scott Ananian; author: Isabelle Hurbain-Palatin):

[mediawiki/extensions/DiscussionTools@wmf/1.46.0-wmf.19] Fix double post-processing in legacy preview case

https://gerrit.wikimedia.org/r/1253551

Change #1253446 merged by jenkins-bot:

[mediawiki/extensions/DiscussionTools@master] Fix double post-processing in legacy preview case

https://gerrit.wikimedia.org/r/1253446

cscott mentioned this in T419830: Signatures aren't properly recognized on ruwiktionary and other projects when using Parsoid, resulting in a missing [ reply ] button.Mon, Mar 16, 4:27 PM

Change #1253560 had a related patch set uploaded (by C. Scott Ananian; author: C. Scott Ananian):

[mediawiki/extensions/VisualEditor@master] Ensure preview parser matches the user's current read views parser

https://gerrit.wikimedia.org/r/1253560

ReleaseTaggerBot added a project: MW-1.46-notes (1.46.0-wmf.20; 2026-03-17).Mon, Mar 16, 5:00 PM

Change #1253551 merged by jenkins-bot:

[mediawiki/extensions/DiscussionTools@wmf/1.46.0-wmf.19] Fix double post-processing in legacy preview case

https://gerrit.wikimedia.org/r/1253551

Mentioned in SAL (#wikimedia-operations) [2026-03-16T20:25:59Z] <cscott@deploy2002> Started scap sync-world: Backport for [[gerrit:1253551|Fix double post-processing in legacy preview case (T419908)]]

Mentioned in SAL (#wikimedia-operations) [2026-03-16T20:27:46Z] <cscott@deploy2002> cscott: Backport for [[gerrit:1253551|Fix double post-processing in legacy preview case (T419908)]] synced to the testservers (see https://wikitech.wikimedia.org/wiki/Mwdebug). Changes can now be verified there.

Mentioned in SAL (#wikimedia-operations) [2026-03-16T20:32:52Z] <cscott@deploy2002> Finished scap sync-world: Backport for [[gerrit:1253551|Fix double post-processing in legacy preview case (T419908)]] (duration: 06m 52s)