Flakes UX: nix run: unusable with --store "{remote}"

[colemickens]

Describe the bug

I am trying to remove my devenv-driven bash scripts by instead wrapping these scripts into derivations and exposing them via nix run.

What I'd like to do is this:

nix run '.#flash-blueline-boot' \
  --eval-store auto \
  --store 'ssh-ng://[email protected]' \
  --override-input mobile-nixos "${HOME}/code/mobile-nixos"

But what I get is:

ls: cannot access '/nix/store/9cr0zplqxzpwcl6blmlz5dpclh3z3mbh-flash-blueline.sh': No such file or directory

Despite:

❯ ssh [email protected] \
  "ls -al /nix/store/9cr0zplqxzpwcl6blmlz5dpclh3z3mbh-flash-blueline.sh"
-r-xr-xr-x 1 root root 292 Jan  1  1970 /nix/store/9cr0zplqxzpwcl6blmlz5dpclh3z3mbh-flash-blueline.sh

This mirrors behavior of using --store in other scenarios where the remote built store path is not copied back.

With nix build I can understand it, but not nix run.

nix version

nix (Nix) 2.8.0pre20220322_d5d4d98

[thufschmitt]

Just a side remark, but you probably don’t want to have nix run always copy back to the local store. For example with --store /some/dir you probably just want to run the thing from your chrooted store.

Maybe that could be solved by #5025 : If we’re able to differentiate the build store and the one used to store the final outputs, then you could do:

nix run '.#flash-blueline-boot' \
  --eval-store auto \
  --build-store 'ssh-ng://[email protected]' \
  --store auto \ # Would probably be the default
  --override-input mobile-nixos "${HOME}/code/mobile-nixos"

[edolstra]

nix run does not support remote execution, and probably won't because the store abstraction doesn't support executing arbitrary commands on a store. It should probably give a nicer error message if the store is not a LocalFSStore.

[colemickens]

Huh, I missed all the replies here. I agree with @thufschmitt's assessment and appreciate the error message that was committed. Thank you!