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Dendritic Pattern

What is the Dendritic Pattern?

The Dendritic pattern is a convention where each file is a self-contained Nix module. Rather than large monolithic files, your configuration becomes a directory tree where each concern lives in its own file.

modules/
  networking.nix       # network config
  openssh.nix          # SSH server
  desktop/
    sway.nix           # window manager
    waybar.nix         # status bar
    notifications.nix  # notification daemon
  users/
    alice.nix           # user account

Each file is a standard Nix module:

{ ... }: {
  services.openssh.enable = true;
  services.openssh.settings.PasswordAuthentication = false;
}

Why Dendritic?

Locality — each concern in its own file, easy to find and modify
Composability — add or remove features by adding or removing files
No boilerplate — import-tree handles the wiring
Git-friendly — file additions don’t cause merge conflicts in import lists
Discoverable — directory structure documents the system

Using with flake-parts

With flake-parts, each file is a flake-parts module:

{
  inputs.import-tree.url = "github:vic/import-tree";
  inputs.flake-parts.url = "github:hercules-ci/flake-parts";

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

{ inputs, ... }: {
  perSystem = { pkgs, ... }: {
    devShells.default = pkgs.mkShell {
      packages = [ pkgs.nil pkgs.nixfmt-rfc-style ];
    };
  };
}

The `/_` Convention

Files under /_ prefixed paths are ignored by default. This gives you a place for shared utilities:

modules/
  feature.nix
  _lib/
    helpers.nix    # not auto-imported

let helpers = import ./_lib/helpers.nix;
in { ... }: { /* use helpers */ }

Further Reading

Dendritic Design — the pattern specification
@mightyiam’s post — introducing the pattern
@drupol’s blog — real-world adoption
Dendrix — index of dendritic aspects

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