I'm seeing a very weird bug with MW 1.35 and the Citizen Skin (uses mustache).
Every page on the wiki has a robots tag containing
<meta name="robots" content="noindex,nofollow">
Using the Timeless with ?useskin=timeless the robot tag disappears (correct behaviour).
I've narrowed it down to line 1019 in Article.php.
... if ( $this->mPage->getId() === 0 || $this->getOldID() ) { ...
If the getOldID() part is removed the correct behaviour is restored.
Alternatively I've expanded the if clause as following, which seems to produce the correct behaviour:
... $isOldRevision = false; # getOldID sometimes returns strings $oldId = (int)$this->getOldID(); $record = $this->mPage->getRevisionRecord(); if ( $record !== null && $oldId !== 0) { $isOldRevision = (int)$record->getId() !== $oldId; } if ( $this->mPage->getId() === 0 || $isOldRevision ) { ...
Trace:
setIndexPolicy: noindex #0 /var/www/html/includes/page/Article.php(889): OutputPage->setIndexPolicy(\'noindex\') #1 /var/www/html/includes/actions/ViewAction.php(74): Article->view() #2 /var/www/html/includes/MediaWiki.php(527): ViewAction->show() #3 /var/www/html/includes/MediaWiki.php(313): MediaWiki->performAction(Object(Article), Object(Title)) #4 /var/www/html/includes/MediaWiki.php(940): MediaWiki->performRequest() #5 /var/www/html/includes/MediaWiki.php(543): MediaWiki->main() #6 /var/www/html/index.php(53): MediaWiki->run() #7 /var/www/html/index.php(46): wfIndexMain() #8 {main}