At present, it is possible for people maintaining packages to omit dependencies from ebuilds when the dependencies are installed on their systems. This is an issue that has personally affected me on Gentoo many times in the past and likely hits every user of both Gentoo and Funtoo at some point.

Proper packaging generally should be verified by installing the package from a minimal stage3, but this is time intensive and seldom done. This results in situations where new users try to install software, but the builds fail, due to the missing dependency.

As an alternative to the status quo, we could implement a feature in portage to track all files accessed during the build process, check them against the dependency list (plus the system set) and report the packages of missed dependencies.

There are a few ways of doing this. One possibility would be through the sandbox. Another possibility might be through cgroups and ftrace/eBPF. This should allow us to collect information on which files are opened. Then the rest should be fairly straightforward by checking them against the portage database. This might be somewhat slow, but it is really only needed for QA, so that should be fine.

This is really an upstream portage issue, but I thought of it following a conversation with drobbins where he encouraged me to think of fundamental improvements, so I am filing this here to track it in Funtoo.