The ParserMigration extension provides an interface for comparing article rendering with a new non-default version of the MediaWiki parser, thus serving as a parser migration tool.

It was deployed on the Wikimedia production cluster during 2018 to compare Tidy-based output with a RemexHTML-based replacement.

In 2023 it was overhauled to compare legacy parser output with Parsoid output.

Add:

wfLoadExtension( 'ParserMigration' );

to your LocalSettings.php to enable.

Running npm test and composer test will run automated code checks.

This extension adds action=parser-migration to the MediaWiki action API, which parses a page with two different parser configurations and returns one or both variants in the API response.

It also adds 'Enable parser migration tool' to the list of 'Developer tools' options at the bottom of the 'Editing' options for a user. When this is enabled, an "Edit with migration tool" link is added to the Tools menu in the sidebar for article pages. Clicking this on an article page will bring up a variant of the "preview edit" page which allows you to compare the legacy parser output against Parsoid output.

== Migration to Parsoid read views ==

This extension also adds a dropdown under 'Developer tools' at the bottom of the 'Editing' options for a user, which allows the user to opt-in, opt-out, or follow the wiki defaults for the use of the new Parsoid wikitext parser to render article pages.

"Follow the wiki default" uses Parsoid based on three configuration options:

• $wgParserMigrationEnableParsoidDiscussionTools if set to true will use Parsoid for all pages in the talk namespace, but not for other pages. This is intended for use with the DiscussionTools extension, which is already powered by Parsoid and enabled by default on some wikis.
• $wgParserMigrationEnableParsoidArticlePages if set to true will use Parsoid for all pages in the main article namespace, but not for other pages.
• $wgParserMigrationEnableParsoidMobileFrontend if set to true will use Parsoid on mobile domains, for pages in the namespaces enabled by the other two options.

The first time the user views a page rendered with the new Parsoid parser, either because they have opted-in to use it always or because the wiki default is to use Parsoid for the particular page they are viewing, a notification will appear. This notification can be controlled with the following configuration options:

• $wgParserMigrationUserNoticeVersion: This value can be incremented whenever the notice text has materially changed, in order to display it again to users who have already dismissed it once.
• $wgParserMigrationUserNoticeDays: After the notice has been manually dismissed by the user, it will not be shown again until this number of days have passed. Setting it to 0 means the notice will never be shown again once dismissed unless the notice version increases.

The message shown is set by two localizable messages, which can also be locally overridden on-wiki:

• parsermigration-notice-title (Override at [[MediaWiki:Parsermigration-notice-title]]) sets the boldfaced title at the top of the notification; setting it to the empty string suppresses the title.
• parsermigration-notice-body (Override at [[MediaWiki:Parsermigration-notice-body]]) sets the body content for the notification. It is recommended that this notice provide a link to https://www.mediawiki.org/wiki/Parsoid/Parser_Unification/Migration for more information.