Merge pull request #44 from feel-co/generator

feat: add config generator options

README.md

@@ -49,6 +49,15 @@ may use to manage individual users' homes by leveraging the module system.
       # This can be used to generate config files with various
       # formats expected by different programs.
       ".config/bar".source = pkgs.writeTextFile "file-foo" "file contents";
+
+      # You can also use generators to transform Nix values
+      ".config/baz" = {
+        # Works with `pkgs.formats` too!
+        generator = lib.generators.toJSON { };
+        value = {
+          some = "contents";
+        };
+      };
     };
   };
 }

flake.nix

@@ -28,7 +28,7 @@
     packages = forAllSystems (system: {
       # Expose the 'smfh' instance used by Hjem as a package in the Hjem flake
       # outputs. This allows consuming the exact copy of smfh used by Hjem.
-      smfh = inputs.smfh.packages.${system}.smfh;
+      inherit (inputs.smfh.packages.${system}) smfh;
     });
 
     checks = forAllSystems (system: let
@@ -56,6 +56,8 @@
         packages = attrValues {
           inherit
             (pkgs)
+            # formatter
+            alejandra
             # cue validator
             cue
             go
@@ -64,6 +66,22 @@
       };
     });
 
-    formatter = forAllSystems (system: nixpkgs.legacyPackages.${system}.alejandra);
+    formatter = forAllSystems (
+      system: let
+        pkgs = nixpkgs.legacyPackages.${system};
+      in
+        pkgs.writeShellApplication {
+          name = "nix3-fmt-wrapper";
+
+          runtimeInputs = [
+            pkgs.alejandra
+            pkgs.fd
+          ];
+
+          text = ''
+            fd "$@" -t f -e nix -x alejandra -q '{}'
+          '';
+        }
+    );
   };
 }

modules/common/user.nix

@@ -9,11 +9,11 @@
   ...
 }: let
   inherit (lib.attrsets) mapAttrsToList;
-  inherit (lib.strings) concatMapStringsSep concatLines;
+  inherit (lib.strings) concatLines concatMapStringsSep;
-  inherit (lib.modules) mkIf mkDefault mkDerivedConfig;
+  inherit (lib.modules) mkDefault mkDerivedConfig mkIf mkMerge;
-  inherit (lib.options) mkOption literalExpression mkEnableOption;
+  inherit (lib.options) literalExpression mkEnableOption mkOption;
   inherit (lib.strings) hasPrefix;
-  inherit (lib.types) attrsOf bool lines listOf nullOr package path str submodule oneOf int;
+  inherit (lib.types) addCheck anything attrsOf bool either functionTo int lines listOf nullOr package path str submodule oneOf;
   inherit (builtins) isList;
 
   cfg = config;
@@ -58,6 +58,32 @@
           description = "Path of the source file or directory";
         };
 
+        generator = lib.mkOption {
+          # functionTo doesn't actually check the return type, so do that ourselves
+          type = addCheck (nullOr (functionTo (either options.source.type options.text.type))) (x: let
+            generatedValue = x config.value;
+            generatesDrv = options.source.type.check generatedValue;
+            generatesStr = options.text.type.check generatedValue;
+          in
+            x != null -> (generatesDrv || generatesStr));
+          default = null;
+          description = ''
+            Function that when applied to `value` will create the `source` or `text` of the file.
+
+            Detection is automatic, as we check if the `generator` generates a derivation or a string after applying to `value`.
+          '';
+          example = literalExpression "lib.generators.toGitINI";
+        };
+
+        value = lib.mkOption {
+          type = nullOr (attrsOf anything);
+          default = null;
+          description = "Value passed to the `generator`.";
+          example = {
+            user.email = "me@example.com";
+          };
+        };
+
         executable = mkOption {
           type = bool;
           default = false;
@@ -90,14 +116,30 @@
         };
       };
 
-      config = {
+      config = let
+        generatedValue = config.generator config.value;
+        hasGenerator = config.generator != null;
+        generatesDrv = options.source.type.check generatedValue;
+        generatesStr = options.text.type.check generatedValue;
+      in
+        mkMerge [
+          {
             target = mkDefault name;
             source = mkIf (config.text != null) (mkDerivedConfig options.text (text:
               pkgs.writeTextFile {
                 inherit name text;
                 inherit (config) executable;
               }));
-      };
+          }
+
+          (lib.mkIf (hasGenerator && generatesDrv) {
+            source = mkDefault generatedValue;
+          })
+
+          (lib.mkIf (hasGenerator && generatesStr) {
+            text = mkDefault generatedValue;
+          })
+        ];
     });
 in {
   imports = [

tests/basic.nix

@@ -6,6 +6,7 @@ in
     nodes = {
       node1 = {
         self,
+        lib,
         pkgs,
         ...
       }: {
@@ -22,9 +23,21 @@ in
           alice = {
             enable = true;
             packages = [pkgs.hello];
-            files.".config/foo" = {
+            files = {
+              ".config/foo" = {
                 text = "Hello world!";
               };
+
+              ".config/bar.json" = {
+                generator = lib.generators.toJSON {};
+                value = {bar = true;};
+              };
+
+              ".config/baz.toml" = {
+                generator = (pkgs.formats.toml {}).generate "baz.toml";
+                value = {baz = true;};
+              };
+            };
           };
         };
 
@@ -47,6 +60,8 @@ in
 
       # Test file created by Hjem
       machine.succeed("[ -L ~alice/.config/foo ]")
+      machine.succeed("[ -L ~alice/.config/bar.json ]")
+      machine.succeed("[ -L ~alice/.config/baz.toml ]")
 
       # Test regular files, created by systemd-tmpfiles
       machine.succeed("[ -d ~alice/user_tmpfiles_created ]")