A home-manager directory that auto-creates dotfile symlinks to it in `~/.config/` based on the file structure

auto-symlinking-nix-directory.md

The code below lets you create a directory in your home-manager config that auto-creates symlinks for non-Nix dotfiles from ~/.config/ using xdg.configFile and mkOutOfStoreSymlink. This gives the following advantages:

1. You can keep all your non-Nix dotfiles in your home-manager repo.
2. You don't have to do home-manager switch on each dotfile change. Changes are instantly reflected.
3. You don't need to hard-code the paths for each symlink, the linking is instead file-based. Just add the new dotfile to the directory, and you're done.

For example, if your home-manager config is in ~/nixos/ and looks like this...:

~/nixos
├── ...
├── flake.nix
└── configs
    ├── starship.toml
    └── fish
        └── config.fish

...then home-mamager will create the following symlinks in ~/.config:

~/.config
├── ...
├── starship.toml -> ~/nixos/configs/starship.toml
└── fish
    └── config.fish -> ~/nixos/configs/fish/config.fish

Don't forget to git add when adding a new dotfile. Otherwise, they will be ignored by Nix. Then run home-manager switch to create the new symlink.

{ config }:
let
  # -------------------------------------------------------------------------
  #   `configsNixPath`: a Nix path type to a directory who's files/directories
  #   should be symlinked to from `~/.config/`.
  #
  #   `configsAbsPath`: an absolute string path to `configsPath`.
  #
  #   The reason this function requires two path parameters to the same
  #   directory is that it uses `builtins.readDir` which would require
  #   `--impure` if only an absolute path were used. If using only a literal
  #   Nix path, the symlinks would point to the Nix store, and thereby require
  #   a build whenever a config file is edited.
  #
  #   `returns`: an attribute set suitable for `xdg.configFile`.
  # -----------------------------------------------------------------
  mkSymlinks =
    configsAbsPath: configsNixPath:
    let
      inherit (config.lib.file) mkOutOfStoreSymlink;

      # Turn relative paths into xdg.configFile entries
      mkSymlink = nixPath: {
        name = nixPath;
        value.source = mkOutOfStoreSymlink "${configsNixPath}/${nixPath}";
      };

      # Recursively read in all files in all subdirectories
      readDirRecursive =
        relPath: nixPath:
        nixPath
        |> builtins.readDir
        |> builtins.attrNames
        |> map (
          name:
          let
            entryType = nixPath |> builtins.readDir |> (entries: entries.${name});
            relPath' = if relPath == "" then name else "${relPath}/${name}";
            nixPath' = "${nixPath}/${name}";
          in
          # Don't include paths to the directories themselves
          if entryType == "directory" then readDirRecursive relPath' nixPath' else [ relPath' ]
        )
        |> builtins.concatLists;
    in readDirRecursive "" configsAbsPath |> map mkSymlink |> builtins.listToAttrs;
in {
  # Change the arguments to point to your `configs` directory
  xdg.configFile = mkSymlinks ./configs "~/nixos/configs";
}

Please let me know if there's some way to improve the implementation so that you only have to pass in one path parameter.

I did some proompting and was able to improve the script to create symlinks recursively for files in any subdirectories, instead of just symlinking the first level of subdirectories themselves. This solves an issue I had with some home-manager modules that themselves generate files in subdirectories ~/.config/, including hyprpaper. I've updated the original gist with my new implementation.