Moving any page results in: TypeError: Return value of TitleArrayFromResult::current() must be an instance of Title, boolean returned
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	Inductiveload
	Sep 9 2021, 10:22 AM

Description

Trying to move any page at Beta enwikisource (e.g. https://en.wikisource.beta.wmflabs.org/wiki/Special:MovePage/Font_tests) results in an error like the following:

[YTngAioMF3gg3mw@WKwbZQAAAAw] /wiki/Special:MovePage/Font_tests TypeError: Return value of TitleArrayFromResult::current() must be an instance of Title, boolean returned

Backtrace:

from /srv/mediawiki/php-master/includes/TitleArrayFromResult.php(75)
#0 /srv/mediawiki/php-master/includes/Title.php(2785): TitleArrayFromResult->current()
#1 /srv/mediawiki/php-master/includes/specials/SpecialMovepage.php(317): Title->hasSubpages()
#2 /srv/mediawiki/php-master/includes/specials/SpecialMovepage.php(212): MovePageForm->showForm(array)
#3 /srv/mediawiki/php-master/includes/specialpage/SpecialPage.php(647): MovePageForm->execute(string)
#4 /srv/mediawiki/php-master/includes/specialpage/SpecialPageFactory.php(1366): SpecialPage->run(string)
#5 /srv/mediawiki/php-master/includes/MediaWiki.php(314): MediaWiki\SpecialPage\SpecialPageFactory->executePath(string, RequestContext)
#6 /srv/mediawiki/php-master/includes/MediaWiki.php(925): MediaWiki->performRequest()
#7 /srv/mediawiki/php-master/includes/MediaWiki.php(559): MediaWiki->main()
#8 /srv/mediawiki/php-master/index.php(53): MediaWiki->run()
#9 /srv/mediawiki/php-master/index.php(46): wfIndexMain()
#10 /srv/mediawiki/w/index.php(3): require(string)
#11 {main}

Also at Beta Commons: https://commons.wikimedia.beta.wmflabs.org/wiki/Special:MovePage/Artturi

Details

	Subject	Repo	Branch	Lines +/-
	title: Avoid calling TitleArray::current on empty iterator	mediawiki/core	master	+1 -4

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Status	Subtype	Assigned	Task
Resolved	BUG REPORT	Jdforrester-WMF	T290640 Undefined variable: wgFileBlacklist
Resolved	Release	• mmodell	T281164 1.37.0-wmf.23 deployment blockers
Resolved	BUG REPORT	Umherirrender	T290642 Moving any page results in: TypeError: Return value of TitleArrayFromResult::current() must be an instance of Title, boolean returned

Event Timeline

Inductiveload created this task.Sep 9 2021, 10:22 AM

Restricted Application added a subscriber: Aklapper. · View Herald TranscriptSep 9 2021, 10:22 AM

Inductiveload updated the task description. (Show Details)Sep 9 2021, 10:24 AM

Tentatively labelling as a blocker
Caused by rMW24d64c755799: docs: Declare UserArray/TitleArray as Iterator<User>/Iterator<Title> by @Umherirrender

Zabe subscribed.Sep 9 2021, 2:53 PM

Change 720069 had a related patch set uploaded (by Umherirrender; author: Umherirrender):

[mediawiki/core@master] title: Avoid calling TitleArray::current on empty iterator

https://gerrit.wikimedia.org/r/720069

gerritbot added a project: Patch-For-Review.Sep 9 2021, 5:16 PM

In T290642#7341955, @DannyS712 wrote:

Caused by rMW24d64c755799: docs: Declare UserArray/TitleArray as Iterator<User>/Iterator<Title> by @Umherirrender

The real type hint was suggested on code review.

TitleArrayFromResult is using Title::newFromRow which always returns a Title object. When the TitleArray is instanced with a valid row, it should return something.
When it is instanced with an empty result set, than it is possible the current() returns false. I am not sure if it is okay to call Iterator functions without checking if the iterator has something to iterate