feat: restructure dev-components/dev-registry with direnv

features/dev.nix

@@ -9,7 +9,6 @@
         pkgs.git
         packages.git-linearize
         packages.ggman
-        pkgs.go
         pkgs.python3
         pkgs.mdbook
         pkgs.marksman
@@ -22,9 +21,5 @@
         pkgs.osc
       ];
 
-      programs.direnv = {
-        enable = true;
-        nix-direnv.enable = true;
-      };
     };
 }

features/direnv/default.nix

@@ -13,4 +13,14 @@
         };
       };
     };
+
+  home = _: {
+    programs.direnv = {
+      enable = true;
+      nix-direnv.enable = true;
+      config.global.hide_env_diff = true;
+    };
+
+    xdg.configFile."direnv/lib/use_dev.sh".source = ./use_dev.sh;
+  };
 }

features/direnv/use_dev.sh

@@ -0,0 +1,80 @@
+# shellcheck shell=bash
+# composable nix devshell from matej.nix
+# usage in .envrc: use dev uv_14 pg_18
+
+# generates a flake and delegates to use_flake at the calling scope
+use_dev() {
+	local nix_list=""
+	for c in "$@"; do
+		if [[ ! "$c" =~ ^[a-zA-Z_][a-zA-Z0-9_]*$ ]]; then
+			log_error "use_dev: invalid component name: $c"
+			return 1
+		fi
+		nix_list="$nix_list \"$c\""
+	done
+
+	local system
+	case "$(uname -s)-$(uname -m)" in
+	Linux-x86_64) system="x86_64-linux" ;;
+	Linux-aarch64) system="aarch64-linux" ;;
+	Darwin-x86_64) system="x86_64-darwin" ;;
+	Darwin-arm64) system="aarch64-darwin" ;;
+	esac
+
+	if [[ -z "$system" ]]; then
+		log_error "use_dev: unsupported platform: $(uname -s)-$(uname -m)"
+		return 1
+	fi
+
+	local dev_path nixpkgs_path registry_filter
+	# shellcheck disable=SC2016 # $id is a jq variable, not shell
+	registry_filter='.flakes[] | select(.from.id == $id) | .to.path'
+
+	local registry_file="${XDG_CONFIG_HOME:-$HOME/.config}/nix/registry.json"
+	if [[ ! -f "$registry_file" ]]; then
+		registry_file="/etc/nix/registry.json"
+	fi
+
+	dev_path="$(jq -re --arg id dev "$registry_filter" "$registry_file" 2>/dev/null)"
+	nixpkgs_path="$(jq -re --arg id nixpkgs "$registry_filter" "$registry_file" 2>/dev/null)"
+
+	if [[ -z "$dev_path" ]]; then
+		log_error "use_dev: 'dev' not found in nix registry"
+		return 1
+	fi
+	if [[ -z "$nixpkgs_path" ]]; then
+		log_error "use_dev: 'nixpkgs' not found in nix registry"
+		return 1
+	fi
+
+	local components_hash project_hash cache_dir
+	components_hash="$(sha256sum "$dev_path/flake/dev-components.nix" 2>/dev/null | cut -c1-16)"
+	project_hash="$(echo "$PWD" | sha256sum | cut -c1-16)"
+	cache_dir="${XDG_CACHE_HOME:-$HOME/.cache}/dev-flakes/$project_hash"
+	mkdir -p "$cache_dir"
+
+	cat >"$cache_dir/flake.nix.tmp" <<DEVFLAKE
+# dev-components: $components_hash
+{
+  inputs.dev = { url = "path:${dev_path}"; flake = false; };
+  inputs.nixpkgs.url = "path:${nixpkgs_path}";
+  outputs = { dev, nixpkgs, ... }:
+    let
+      system = "${system}";
+      pkgs = nixpkgs.legacyPackages.\${system};
+      devLib = import "\${dev}/flake/dev-components.nix" { inherit pkgs; lib = nixpkgs.lib; };
+    in {
+      devShells.\${system}.default = devLib.mkComponentShell [$nix_list ];
+    };
+}
+DEVFLAKE
+
+	if ! cmp -s "$cache_dir/flake.nix.tmp" "$cache_dir/flake.nix" 2>/dev/null; then
+		mv "$cache_dir/flake.nix.tmp" "$cache_dir/flake.nix"
+		rm -f "$cache_dir/flake.lock"
+	else
+		rm "$cache_dir/flake.nix.tmp"
+	fi
+
+	use_flake "path:$cache_dir"
+}

flake/dev-components.nix

@@ -0,0 +1,111 @@
+# composable dev environment components
+# imported by generated per-project flakes via use_dev
+{ pkgs, lib }:
+let
+  # libraries needed by python native extensions
+  pythonLibraries = [
+    pkgs.stdenv.cc.cc.lib
+    pkgs.zlib
+    pkgs.openssl
+    pkgs.curl
+  ];
+
+  mkNode = nodejs: {
+    packages = [
+      nodejs
+      pkgs.corepack
+    ];
+    env = {
+      COREPACK_ENABLE_STRICT = "0";
+    };
+  };
+
+  mkUv = python: {
+    packages = [
+      python
+      pkgs.uv
+    ];
+    libraries = pythonLibraries;
+    env = {
+      UV_PYTHON_DOWNLOADS = "never";
+      UV_PYTHON_PREFERENCE = "only-system";
+      UV_PYTHON = "${python}/bin/python";
+    };
+    shellHook = ''
+      unset PYTHONPATH
+      export UV_PROJECT_ENVIRONMENT="''${XDG_DATA_HOME:-$HOME/.local/share}/dev-venvs/$(basename "$PWD")-$(echo "$PWD" | sha256sum | cut -c1-8)"
+    '';
+  };
+
+  components = {
+    uv_10 = mkUv pkgs.python310;
+    uv_11 = mkUv pkgs.python311;
+    uv_12 = mkUv pkgs.python312;
+    uv_13 = mkUv pkgs.python313;
+    uv_14 = mkUv pkgs.python314;
+
+    pg_15 = {
+      packages = [ pkgs.postgresql_15 ];
+    };
+    pg_16 = {
+      packages = [ pkgs.postgresql_16 ];
+    };
+    pg_17 = {
+      packages = [ pkgs.postgresql_17 ];
+    };
+    pg_18 = {
+      packages = [ pkgs.postgresql_18 ];
+    };
+
+    node_20 = mkNode pkgs.nodejs_20;
+    node_22 = mkNode pkgs.nodejs_22;
+    node_24 = mkNode pkgs.nodejs_24;
+
+    go = {
+      packages = [ pkgs.go ];
+    };
+
+    rust = {
+      packages = [
+        pkgs.rustc
+        pkgs.cargo
+        pkgs.rust-analyzer
+        pkgs.openssl
+        pkgs.pkg-config
+      ];
+    };
+
+    cmake = {
+      packages = [
+        pkgs.cmake
+        pkgs.ninja
+      ];
+    };
+  };
+
+  # build a single mkShell from one or more component names
+  mkComponentShell =
+    names:
+    let
+      selected = map (n: components.${n}) names;
+      allPackages = lib.concatMap (c: c.packages or [ ]) selected;
+      allLibraries = lib.concatMap (c: c.libraries or [ ]) selected;
+      allHooks = lib.concatMapStrings (c: c.shellHook or "") selected;
+      allEnvs = lib.foldl' (acc: c: acc // (c.env or { })) { } selected;
+      libPath = lib.makeLibraryPath allLibraries;
+    in
+    pkgs.mkShell (
+      {
+        packages = allPackages;
+        shellHook =
+          (lib.optionalString (allLibraries != [ ]) ''
+            export LD_LIBRARY_PATH="${libPath}''${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
+          '')
+          + allHooks;
+      }
+      // lib.optionalAttrs (allEnvs != { }) { env = allEnvs; }
+    );
+in
+{
+  inherit components mkComponentShell;
+}

flake/devshell.nix

@@ -1,93 +1,6 @@
 _: {
   perSystem =
-    { pkgs, lib, ... }:
+    { pkgs, ... }:
-    let
-      # libraries needed by python native extensions
-      pythonLibraries = [
-        pkgs.stdenv.cc.cc.lib
-        pkgs.zlib
-        pkgs.openssl
-        pkgs.curl
-      ];
-
-      mkUv = python: {
-        packages = [
-          python
-          pkgs.uv
-        ];
-        libraries = pythonLibraries;
-        env = {
-          UV_PYTHON_DOWNLOADS = "never";
-          UV_PYTHON_PREFERENCE = "only-system";
-          UV_PYTHON = "${python}/bin/python";
-        };
-        shellHook = ''
-          unset PYTHONPATH
-          export UV_PROJECT_ENVIRONMENT="$HOME/.venvs/$(basename "$PWD")-$(echo "$PWD" | md5sum | cut -c1-8)"
-        '';
-      };
-
-      # composable dev environment components
-      # each is exposed as its own devShell, layered via `use dev` in .envrc
-      components = {
-        uv_10 = mkUv pkgs.python310;
-        uv_11 = mkUv pkgs.python311;
-        uv_12 = mkUv pkgs.python312;
-        uv_13 = mkUv pkgs.python313;
-        uv_14 = mkUv pkgs.python314;
-
-        pg_15 = {
-          packages = [ pkgs.postgresql_15 ];
-        };
-        pg_16 = {
-          packages = [ pkgs.postgresql_16 ];
-        };
-        pg_17 = {
-          packages = [ pkgs.postgresql_17 ];
-        };
-        pg_18 = {
-          packages = [ pkgs.postgresql_18 ];
-        };
-
-        rust = {
-          packages = [
-            pkgs.rustc
-            pkgs.cargo
-            pkgs.rust-analyzer
-            pkgs.openssl
-            pkgs.pkg-config
-          ];
-        };
-
-        cmake = {
-          packages = [
-            pkgs.cmake
-            pkgs.ninja
-          ];
-        };
-      };
-
-      mkComponentShell =
-        component:
-        let
-          c = components.${component};
-          libraries = c.libraries or [ ];
-          libPath = lib.makeLibraryPath libraries;
-        in
-        pkgs.mkShell (
-          {
-            packages = c.packages or [ ];
-            shellHook =
-              (lib.optionalString (libraries != [ ]) ''
-                export LD_LIBRARY_PATH="${libPath}''${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}"
-              '')
-              + (c.shellHook or "");
-          }
-          // lib.optionalAttrs (c ? env) { inherit (c) env; }
-        );
-
-      componentShells = lib.mapAttrs (name: _: mkComponentShell name) components;
-    in
     {
       formatter = pkgs.nixfmt-tree;
 
@@ -103,7 +16,6 @@ _: {
             pkgs.ssh-to-age
           ];
         };
-      }
+      };
-      // componentShells;
     };
 }

flake/hosts.nix

@@ -30,7 +30,7 @@ in
         "yubikey"
         "calibre"
         "steam"
-        "dev-registry"
+        "direnv"
         "neovim"
         "dev"
         "claude"
@@ -57,7 +57,7 @@ in
         "calibre"
         "steam"
         "initrd-ssh"
-        "dev-registry"
+        "direnv"
         "neovim"
         "dev"
         "claude"

lib/mkHost.nix

@@ -16,7 +16,13 @@ let
   hasUser = user != null;
 
   # path helpers
-  featurePath = f: ../features/${f}.nix;
+  featurePath =
+    f:
+    let
+      file = ../features/${f}.nix;
+      dir = ../features/${f};
+    in
+    if builtins.pathExists file then file else dir;
   userFeaturePath = u: ../features/user-${u}.nix;
   hostConfig = ../hosts/${name}/configuration.nix;
   hostHWConfig = ../hosts/${name}/hardware-configuration.nix;