View source for Category talk:Pages with template loops

== [[m:Special:MyLanguage/Tech/News/2017/14|Tech News: 2017-14]] ==
{{hatnote|Copied from {{section link|Wikipedia:Village pump (technical)/Archive 154#Tech News: 2017-14}}}}

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Latest '''[[m:Special:MyLanguage/Tech/News|tech news]]''' from the Wikimedia technical community. Please tell other users about these changes. Not all changes will affect you. [[m:Special:MyLanguage/Tech/News/2017/14|Translations]] are available.

'''Recent changes'''
* The tracking category [[:{{ns:14}}:{{MediaWiki:Template-loop-category}}]] is now added when a template loop is found. A template loop is for example when a template tries to use a second template that uses the first template. [https://phabricator.wikimedia.org/T160743]
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== Category:Pages with template loops ==
{{hatnote|Copied from {{section link|Wikipedia:Village pump (technical)/Archive 154#Category:Pages with template loops}}}}

Per the above tech news, [[:Category:Pages with template loops]] now exists to track pages with template loops in them. Some documentation on that Category page about how to fix template loops, assuming that they are a problem, would be welcome. – [[User:Jonesey95|Jonesey95]] ([[User talk:Jonesey95|talk]]) 21:32, 3 April 2017 (UTC)
:What's the difference between that category, and [[:Category:Template loop warnings]]? Problems in the latter category are usually easy to understand. [[User:Wbm1058|wbm1058]] ([[User talk:Wbm1058|talk]]) 21:38, 3 April 2017 (UTC)
::The new [[:Category:Pages with template loops]] automatically tracks all pages where a template loop was encountered during rendering. It may populate slowly as pages are rendered. It can take months before a page is rendered if it isn't edited. The English Wikipedia has added [[:Category:Template loop warnings]] in [[MediaWiki:Parser-template-loop-warning]] since 2009 (the default message has no category). However, the category is only added if [[MediaWiki:Parser-template-loop-warning]] is displayed in the rendered page and that only happens if a page tries to display the result of a template loop. For example, on page X the code <code><nowiki>{{X}}</nowiki></code> will produce the message and therefore the category. But the code <code><nowiki>{{#if:{{X}}|A|B}}</nowiki></code> will not try to display <code><nowiki>{{X}}</nowiki></code> which will just evaluate to a non-empty error message during processing, so the <code>#if</code> will display <code>A</code>. [[:Category:Template loop warnings]] is not added in this case but [[:Category:Pages with template loops]] is. The former should be a subset of the latter, at least when [[:Category:Pages with template loops]] has been fully populated. We could also "merge" the two categories by removing our old category from [[MediaWiki:Parser-template-loop-warning]] (we could still keep the name by creating [[MediaWiki:Template-loop-category]] with it). [[User:PrimeHunter|PrimeHunter]] ([[User talk:PrimeHunter|talk]]) 00:23, 4 April 2017 (UTC)
:I picked a page in [[:Category:Pages with template loops]], [[Postbellum]], to track down the problem.
:Next I isolated the code that was generating the error: <code><nowiki>{{Language with name/for||Latin|"after the war"}}</nowiki></code> (trial & error to do that, as there's no obvious error message)
:Digging deeper into that, I found:
:*<code><nowiki>{{#ifexist: {{ISO 639 name|}} }}</nowiki></code> (with a blank parameter) silently populates [[:Category:Pages with template loops]]
:*<code><nowiki>{{ISO 639 name|}}</nowiki></code> populates [[:Category:Template loop warnings]] and writes the message: {{red|Template loop detected}}: Template:ISO 639 name
: I'll try to patch [[Template:ISO 639 name]] to make the error go away. – [[User:Wbm1058|wbm1058]] ([[User talk:Wbm1058|talk]]) 22:52, 3 April 2017 (UTC)
::[[Template_talk:ISO_639_name#Loop_error_with_blank_parameter|A fix may already be in that template's sandbox]] from three years ago. – [[User:Jonesey95|Jonesey95]] ([[User talk:Jonesey95|talk]]) 23:19, 3 April 2017 (UTC)
:::[[special:diff/773714136|This patch]] cleared the problem from [[Postbellum]]. – [[User:Wbm1058|wbm1058]] ([[User talk:Wbm1058|talk]]) 23:21, 3 April 2017 (UTC)
::::Yuck. Fix one issue and the side-effect of that is to introduce another. Now there are a ton of false-positive {{tl|error}} transclusions.
::::Taking this off the village pump; see [[Template talk:ISO 639 name/Archive 1#Return empty string for codes not on the list|Template talk:ISO 639 name#Return empty string for codes not on the list]]. {{ping|Jonesey95}} you may be interested in this as I see you created [[:Category:Articles containing unknown ISO 639 language template]]. – [[User:Wbm1058|wbm1058]] ([[User talk:Wbm1058|talk]]) 18:33, 4 April 2017 (UTC)