== PageNameFormula — a MediaWiki extension ==

PageNameFormula is an extension that provides a page_name_formula that will rename a page based on a formula if any template field within the formula has changed.

The idea comes from Yaron Koren during [https://www.mediawiki.org/wiki/EMWCon_Spring_2017 EMWCon Spring 2017] as a project for the Create Camp day.

I (Mark Hershberger) decided to use the extension as an example for how to build an extension.

== Examples ==

Supppose you have a page with the name <tt>Main_Page</tt> and it includes <tt><nowiki>{{#page_name_formula:{{Main_Page_Name}}}}</nowiki></tt> in the wikitext of the page.

=== first save ===
The first time you save,
# the result of the <tt><nowiki>{{Main_Page_Name}}</nowiki></tt> template would be checked,
# the current name (<tt>Main_Page</tt>) and revision number is stored in the <tt>page_name_mapping</tt> database table, and
# if the template resulted in anything but <tt>Main_Page</tt>, then the page is added to the [https://www.mediawiki.org/wiki/Manual:Job_queue job queue] to be renamed.

=== renaming job ===
When a page renaming job is found in the [https://www.mediawiki.org/wiki/Manual:Job_queue job queue],
# the page is renamed using the [https://doc.wikimedia.org/mediawiki-core/master/php/classMovePage.html MovePage] class,
# the new name (<tt>Main_Page</tt>) and revision number is stored in the <tt>page_name_mapping</tt> database table, and
# unless otherwise specified, a redirect is left in place, and
# any double redirects are fixed, unless <tt>[https://www.mediawiki.org/wiki/Manual:$wgFixDoubleRedirects $wgFixDoubleRedirects]</tt> is false.

=== when page renames are made ===