How to represent absolute paths to binaries?

[m3thm4th]

For example the absolute path to Thunderbird from the Nix repo would be ${pkgs.thunderbird}/bin/thunderbird
What would be the equivalent for the flatpak org.mozilla.Thunderbird?

[gmodena]

What are you trying to achieve?

The typical path for a Flatpak application will be within the ~/.local/share/flatpak/app directory for user installations, or /var/lib/flatpak/app for system wide ones.

Each application is built and run in an isolated environment (the sanbox), installed side-by-side nix store.

nix will not be aware of those environments, but if you want to find the absolute path for an executable you can query flatpak directly with:

flatpak info --show-location org.mozilla.Thunderbird.

[m3thm4th]

So basically it will be /var/lib/flatpak/app because they are non-generational, the path variable would be needed with other projects like this one where Flatpaks are generational, correct?

[gmodena]

I'm not sure how the implementation you linked handles things these days, but the path isn't related to the fact that nix-flatpak is not generational.

Flatpak (upstream) uses its own directory layout to store its application sandboxes outside of the Nix store. Nix, and its tooling, won't be aware of those binaries.