Implement top-level __findFile

[jwiegley]

No description provided.

[drets]

If it is still relevant I would like to try to tackle it.

Should it work something like this?

hnix:master* λ ./dist/build/hnix/hnix --eval --expr "builtins.findFile nixpkgs/default.nix"
/home/drets/src/dots/channels/nixpkgs/default.nix

hnix:master* λ ./dist/build/hnix/hnix --eval --expr "builtins.findFile nixpkgs/blah.nix"
error: file 'nixpkgs/blah.nix' was not found in the Nix search path (add it using $NIX_PATH or -I)

[shlevy]

@drets No, findFile takes an explicit set corresponding to the NIX_PATH. nix-instantiate --eval -E builtins.nixPath --strict can show you what that argument looks like, basically it's a list of sets, where each set has a path attribute and an optional prefix. Given prefix = "foo" and path = /bar, <foo/baz> will resolve to /bar/baz. Given no prefix, or an empty string, and path = /bar, and given /bar/foo exists, <foo/baz> will resolve to /bar/foo/baz

[drets]

@shlevy, thank you.

It seems, I figured out how it works:

~ λ nix-instantiate --eval -E "builtins.nixPath" --strict
[ { path = "/home/drets/src/dots/nixos/configuration.nix"; prefix = "nixos-config"; } { path = "/home/drets/src/dots/channels"; prefix = ""; } { path = "/nix/store/2xzhrn49hzcpkg72sgqh6qdx0klckssv-nix-2.0/share/nix/corepkgs"; prefix = "nix"; } ]
~ λ nix-instantiate --eval -E 'builtins.findFile builtins.nixPath "nixpkgs/default.nix"' --strict
/home/drets/src/dots/channels/nixpkgs/default.nix
~ λ nix-instantiate --eval -E 'builtins.findFile builtins.nixPath "nixos-config"' --strict
/home/drets/src/dots/nixos/configuration.nix
~ λ nix-instantiate --eval -E 'builtins.findFile builtins.nixPath "nixpkgs/blah.nix"' --strict
error: file 'nixpkgs/blah.nix' was not found in the Nix search path (add it using $NIX_PATH or -I), at (string):1:1