Background

It is possible to create pages and sections with preloaded text, using the preload URL parameter.

When a translateable page is the target of the preload param, it would be helpful to fall back to an appropriate language if a particular translation does not exist. For an example of where we might want to do this, see T296272#7619882.

We can do this using Special:MyLanguage, which redirects to a translated version of a given page in the user's language, using the fallback chain if a translation is missing in that language.

Acceptance criteria

When the target of the preload param is a translateable page for a language that does not yet have a translation, the page for the next available language in the fallback chain is preloaded instead. This should work for:

• action=edit https://gerrit.wikimedia.org/r/755335
• veaction=edit and veaction=editsource https://gerrit.wikimedia.org/r/c/mediawiki/extensions/VisualEditor/+/755926

Notes

Requirements for testing:

• Translate extension (see configuration docs and related pages)

Example steps for testing (non-VisualEditor):

• Create a page e.g. TranslateablePage, and translate it into a language that other languages fall back to (helpful tutorial here), e.g. TranlsateablePage/fr
• Create a new page with this page preloaded, with the language set to one that falls back to the translated language, e.g. NewPage?action=edit&preload=Special:MyLanguage/TranslateablePage&uselang=frp (frp falls back to fr)
• Expected: The editor for NewPage is pre-filled with the contents of TranslateablePage/fr (assuming no tranlsation exists for frp)

Example steps for testing (VisualEditor):

• Requires the VisualEditor extension: https://www.mediawiki.org/wiki/Extension:VisualEditor#Setting_up_VisualEditor
• Do as above, but with veaction=edit and veaction=editsource, instead of action=edit