nix print-dev-env --profile should include flake inputs

[Mic92]

Is your feature request related to a problem? Please describe.

When using nix print-dev-env in tools like direnv the nix shell is cached and --profile adds a gc root to prevent garbage collection. However all inputs are still garbage collected every 15 minutes (?), which makes working with bad/no internet harder/impossible.

Describe the solution you'd like

the --profile parameter should also add a garbage collection root for all (evaluated?) flake inputs.

Describe alternatives you've considered

Do it manually using some script doing: nix flake archive --json | grep -P -o -m1 '(?<="path":")/nix/store[^"]+' and then add a gc root for all inputs.

[stale]

I marked this as stale due to inactivity. → More info

[Mic92]

I sort of fixed this for nix-direnv: nix-community/nix-direnv@763d572

[stale]

I marked this as stale due to inactivity. → More info

[Mic92]

Still an issue. Only with nix-direnv it is possible to get an development environment that works off-the-grid (no internet).

[stale]

I marked this as stale due to inactivity. → More info

[nrdxp]

Perhaps to make this more general, and because print-dev-env is basically just building a devShell output and exporting it in a special format anyway, we should probably rename this to "add flake inputs to --profile closure" or something along those lines. It'd be great if registering a profile (and gc root) for any package would also give us any flake inputs required to build that package.

I have a few flakes where even nix-direnv doesn't seem to cache all flake inputs. Much better if nix was internally aware of what was required to fetch to build something and include all of that in the profile closure