Migrate to Den

Strategy

Migration to Den is incremental. You do not need to rewrite everything at once.

1. Add Den as Input

   Add Den to your flake and import the flake module:

   {
     inputs.den.url = "github:vic/den";
     inputs.import-tree.url = "github:vic/import-tree";
   
     outputs = inputs: inputs.flake-parts.lib.mkFlake { inherit inputs; }
       (inputs.import-tree ./modules);
   }

   modules/den.nix

   { inputs, ... }: {
     imports = [ inputs.den.flakeModule ];
   }

2. Declare Hosts

   Move your host declarations into den.hosts:

   {
     den.hosts.x86_64-linux.laptop.users.alice = { };
   }

3. Import Existing Modules

   Use den.provides.import-tree to load your existing non-dendritic modules:

   modules/legacy.nix

   { den, ... }: {
     den.ctx.host.includes = [
       (den.provides.import-tree._.host ./hosts)
     ];
     den.ctx.user.includes = [
       (den.provides.import-tree._.user ./users)
     ];
   }

   With this directory structure:

   hosts/
     laptop/
       _nixos/
         hardware.nix
         networking.nix
       _homeManager/
         shell.nix
   users/
     alice/
       _homeManager/
         git.nix
       _nixos/
         groups.nix

   Files under _nixos/ are imported as NixOS modules, _homeManager/ as Home Manager modules, etc. This requires inputs.import-tree.

4. Extract Aspects

   Gradually extract features from your legacy modules into Den aspects:

   modules/dev-tools.nix

   {
     den.aspects.dev-tools = {
       nixos = { pkgs, ... }: {
         environment.systemPackages = with pkgs; [ git vim tmux ];
       };
       homeManager.programs.git.enable = true;
     };
   }

   modules/laptop.nix

   { den, ... }: {
     den.aspects.laptop.includes = [ den.aspects.dev-tools ];
   }

5. Remove Legacy

   As aspects replace legacy modules, remove the corresponding files from hosts/ and users/. Eventually remove den.provides.import-tree usage.

Tips

• Start with one host. Migrate a single machine first to learn the pattern.
• Keep legacy working. import-tree loads your existing files alongside Den aspects — they coexist without conflicts.
• Use batteries. Replace manual user/shell/HM setup with den.provides.*.
• Test with VM. Use nix run .#vm to validate changes before applying to hardware.