Portal for housekeeping

[hanaral]

Problem

Currently housekeeping with flatpaks only effect trashed files, but that isn't the only thing housekeeping already has as a feature.

Proposal

Create a portal for the system to housekeep apps' cache and tmp files under their name in the ~/.var/app/ directory. The user and the system already have access to those files; I image that developers could have some kind of flag either in the .desktop (or elsewhere) saying that their app can be housekept by providing a location of temporary files.
Of course there is the obvious 'nuke cache folder' option (by completely emptying the pictured dir.), which could potentially be harmful, hence why it should be opt-in

To be fair, I'm not sure if this even needs to be a portal - could't there be an OS component that manually removes these files that are flagged as 'housekeepable'?

Prior Art

[Marukesu]

I don't think what is beginning suggested here is a portal, portals are to allow the sandbox interact with the host, not the inverse.

What's beginning proposed here is a way to applications tell the host that "this folder should be cleanup automatically" and that don't need to be an portal.

Also, I don't think we need this, we could just recommend that flatpak applications set they TPMDIR to XDG_CACHE_DIR/tmp and we handle that with tmpfiles. we are doing that with downloads already.

[hanaral]

I wasn't aware that temporary files could remain after the application is closed