Paths referenced by plugins.luasnip.from{Lua,Snipmate,Vscode}.*.paths are removed by nix store gc

[cezdro]

I configured the snippet path using the relative path like in the example. However, at one point the snippets stopped working and I figured that it happened because Nix thought the directory was only needed at a build time and could now be GC'd (I have nix.gc.automatic enabled). Here is the snippet from the generated init.lua:

require("luasnip.loaders.from_lua").lazy_load({
    ["paths"] = "/nix/store/1wm0qsxvri2pdxd67sxa569inz4pl385-f5jcwka5bpj542475ib1kgfplgnb9x8n-source/modules/home/nvim/plugins/luasnip",
})

require("luasnip.loaders.from_snipmate").lazy_load({
    ["paths"] = "/nix/store/1wm0qsxvri2pdxd67sxa569inz4pl385-f5jcwka5bpj542475ib1kgfplgnb9x8n-source/modules/home/nvim/plugins/luasnip",
})

require("luasnip.loaders.from_vscode").lazy_load({
    ["paths"] = "/nix/store/1wm0qsxvri2pdxd67sxa569inz4pl385-f5jcwka5bpj542475ib1kgfplgnb9x8n-source/modules/home/nvim/plugins/luasnip",
})

I don't know how Nix decides whether the referenced path should be kept or not. I think that if I used mkDerivation the directory wouldn't be treated as a garbage, but I don't think that such thing should be necessary in Nixvim config.

I wrote this in Discussions, because I don't know if this is my fault and if it can be improved in Nixvim.

[MattSturgeon]

I don't have a full grasp on this, but it's definitely unfortunate if paths referenced in a nixvim config aren't treated as persistent runtime dependencies...

Reading this nix pill, it seems nix usually figures it out automagically. However I wonder if, bucause the path is to a -source type derivation, perhaps things are treated differently?

In a nixpkgs style derivation all runtime/installed files will have been copied to the builder's $out path.

Looking at how nixos handles paths in (for example) its etc module, it seems they ensure all referenced paths are copied (not symlinked) into the final derivation. We do the same thing in our extraFiles module:

nixvim/modules/top-level/files/default.nix

Lines 70 to 92 in 9c11b54

	# A directory with all the files in it
	# Implementation based on NixOS's /etc module
	filesPlugin = pkgs.runCommandLocal "nvim-config" { } ''
	set -euo pipefail
	makeEntry() {
	src="$1"
	target="$2"
	mkdir -p "$out/$(dirname "$target")"
	cp "$src" "$out/$target"
	}
	mkdir -p "$out"
	${lib.concatMapStringsSep "\n" (
	{ target, finalSource, ... }:
	lib.escapeShellArgs [
	"makeEntry"
	# Force local source paths to be added to the store
	"${finalSource}"
	target
	]
	) extraFiles}
	'';

My first thought is that maybe any module allowing path type options should be coercing them into a derivation owned by the module implementing the option, but I feel like we'd need to discuss the issue with some experts to get a better understanding of the situation.

As an initial workaround, does doing something like builtins.toFile "filename" (builtins.readFile ./srcFile) help at all?

[cezdro]

I ended up doing this:

{ pkgs, ... }: let
  snippets = pkgs.stdenv.mkDerivation {
    name = "snippets";

    src = ./.;

    buildCommand = ''
      mkdir $out
      cp -r $src/*.{json,lua,snippets} $out
    '';
  };
in {
  programs.nixvim = {
    plugins.luasnip = {
      enable = true;

      fromLua = [{paths = "${snippets}";}];
      fromSnipmate = [{paths = "${snippets}";}];
      fromVscode = [{paths = "${snippets}";}];
    };
  };
}

The "snippets" derivation isn't removed on nix store gc. Anyway, I still think this is something that Nixvim could do automatically.

[cezdro]

I created an issue from this discussion: #2179