Description

Allow for Wikifunctions calls in WIkipedia to set empty values for inputs of "Gregorian calendar date/Z20420", which would be interpreted by default as the current date.

Acceptance criteria

• Functions which take Gregorian calendar date input types should allow empty values which will be interpreted as today's date in the client wiki locale.

Subtasks

• T391019 [Spike]: decide whether to set default values in the client or in the server, contemplate pros and cons of both solutions
• T391021 [Wikilambda]: implement setting of date default value to today's day
  • If we set args in client:
    • ClientHooks: request function from Wikifunctions and replace empty argument with default value
    • ClientHooks: adapt caching strategy to new default value features
• T391023 [VisualEditor Wikifunctions]: allow dates with empty values without stopping them on validation
• T391077 [Design]: investigate effects of displaced Wikifunctions default values user guidance

Completion checklist

• Before closing this Epic, review one by one the checklist available here: https://www.mediawiki.org/wiki/Abstract_Wikipedia_team/Definition_of_Done#CUJ/Epic_completion_checklist