Problem/Motivation
The critical need
As documented in #3051352: [Plan] Remove unused jQuery UI components and replace with a suite of contrib packages for the continuous upgrade path, jQueryUI is deprecated in Drupal9 core. In Drupal 9, contrib themes dependent on jQueryUI should be satisfying their jQueryUI requirements via the contrib jQueryUI modules. It needs to be possible for these themes to declare these contrib modules as dependencies.
Additional motivation
Parsing .info files for dependency information is already implemented on the modules administration page. Adding support for the same dependencies in theme.info files, and implementing the same behavior on the admin/build/themes page, would allow designers building heavily customized themes to make safer assumptions about their target sites.
A theme might require the existence of imagecache to auto-generate variations of a header image. This would be a nice compromise between systems like Wordpress and Joomla!, which give themes much greater control over the functionality of the site, and Drupal's module-centric approach.
Proposed resolution
- Allow themes to add the dependencies to
.info.ymlfiles - Show these dependencies on /admin/appearance and make it impossible to install without the requirements via UI or command line
Install dependencies automatically on API level.Moved to followup #3100374: Make it possible to install dependent modules when installing theme- Validation is added to prevent installing themes that depend on uninstalled modules, and prevent uninstalling modules that are depended upon by installed themes. This is implemented at a level that prevents these installs/uninstalls from occurring programatically or via cli (Drush/Drupal Console).
Follow-ups
- #3100374: Make it possible to install dependent modules when installing theme
- Update #3005229: Provide optional support for using composer.json for dependency metadata to read composer.json theme's also
User interface changes
Themes listed in admin/appearance will list the modules they depend on and the ability to install that theme will not be available unless those module dependencies are met.
The module descriptions found at admin/modules and admin/module/uninstall will include themes in their "Required By" description.
API changes
Themes will be able to define modules dependencies in their info.yml via the dependencies key.
Release notes snippet
Pending.
Original report by [eaton]
Issue Summary
Parsing .info files for dependency information is already implemented on the modules administration page. Adding support for the same dependencies in theme.info files, and implementing the same behavior on the admin/build/themes page, would allow designers building heavily customized themes to make safer assumptions about their target sites.
A theme might require the existence of imagecache to auto-generate variations of a header image. This would be a nice compromise between systems like Wordpress and Joomla!, which give themes much greater control over the functionality of the site, and Drupal's module-centric approach.