Idea: allow "pinning" base themes to specific versions (to solve the issue with breaking changes in core themes)

This idea was initiated by @BWPanda in Zulip: https://backdrop.zulipchat.com/#narrow/stream/218635-Backdrop/topic/Core...

The Olivero theme is not backwards compatible

I think that's the kicker. In Backdrop, we tend to be more desiring backwards-compatibility. Perhaps we could adopt a compromise instead - fork Basis and mark it 'not backwards-compatible', then include it by default in core for new sites going forward. This new version would get all the new features, fixes, etc. and would put an end to the issues we have with updating Basis currently. The old, backwards-compatible version of Basis would remain in core (or perhaps just contrib?) for posterity and for existing sites, but marked as such so people know they can use it for subtheming but it won't receive updates.

@herbdool

That could work. Then if someone wants to use the new one they could copy the whole theme and rename functions etc?

@klonos

I thought that before each minor release, we could be grabbing the current core basis theme folder and dumping it to contrib, as a new versioned branch/release. Then people could either choose to subtheme as they currently do now, by simply by using base theme = basis in the .info file of their subtheme (which would always get them the core version, and which may introduce breaking changes in the future), or they could also be doing something like dependencies = basis (1.23.0) (which would "pin" their base theme to a specific version - which would only be provided by the contrib theme). ...or something like that anyway ...if dependencies requires too much refactoring to support all that, then we could come up with a new property in the .info file, like pin base theme = 1.23.0. ...or just have the existing base theme property support versions.