fix: on-unmatched option

checks/default.nix

@@ -10,6 +10,14 @@ let
       programs.${name}.enable = true;
     };
 
+  # Generate example config with only the formatter section (no default excludes)
+  toExampleConfig =
+    name:
+    treefmt-nix.mkConfigFile pkgs {
+      enableDefaultExcludes = false;
+      programs.${name}.enable = true;
+    };
+
   # Helper to get meta attributes for a specific formatter
   getFormatterMeta =
     name:
@@ -78,23 +86,23 @@ let
     }) usableFormatterNames
   );
 
+  # Example configs without default excludes
+  exampleConfigs = lib.listToAttrs (
+    map (name: {
+      name = "formatter-${name}";
+      value = toExampleConfig name;
+    }) (lib.filter (n: !shouldSkipExample n) usableFormatterNames)
+  );
+
   examples =
     let
-      configs =
-        lib.mapAttrs
-          (name: value: ''
-            {
-              echo "# Example generated by ../examples.sh"
-              sed -n '/^$/q;p' ${value} | sed 's|\(command = "\).*/\([^"]\+"\)|\1\2|' | sed 's|/nix/store/.*-||'
-            } > "$out/${name}.toml"
-          '')
-          (
-            lib.filterAttrs (
-              n: _:
-              # Filter out formatters to skip in example generation
-              !shouldSkipExample (lib.removePrefix "formatter-" n)
-            ) programConfigs
-          );
+      configs = lib.mapAttrs (name: value: ''
+        {
+          echo "# Example generated by ../examples.sh"
+          # Clean up store paths from command
+          sed 's|\(command = "\).*/\([^"]\+"\)|\1\2|' ${value} | sed 's|/nix/store/.*-||'
+        } > "$out/${name}.toml"
+      '') exampleConfigs;
     in
     pkgs.runCommand "examples" { } ''
       mkdir $out

module-options.nix

@@ -23,32 +23,47 @@ let
 
   configFormat = pkgs.formats.toml { };
 
+  # Remove keys in the setting that are "empty" to keep the config file lean
+  emptySettingsKeys =
+    lib.optional (config.settings.excludes == [ ]) "excludes"
+    ++ lib.optional (config.settings.on-unmatched == null) "on-unmatched"
+    # Remove deprecated 'global' key (created by mkRenamedOptionModule for backwards compatibility)
+    ++ [ "global" ];
+
+  settingsData = builtins.removeAttrs config.settings emptySettingsKeys;
+
+  configFile = configFormat.generate "treefmt.toml" settingsData;
+
   # The schema of the treefmt.toml data structure.
   configSchema = mkOption {
     default = { };
     description = "The contents of treefmt.toml";
     type = types.submodule {
+      imports = [
+        (lib.mkRenamedOptionModule [ "global" "excludes" ] [ "excludes" ])
+        (lib.mkRenamedOptionModule [ "global" "on-unmatched" ] [ "on-unmatched" ])
+      ];
       freeformType = configFormat.type;
       options = {
-        global = {
-          excludes = mkOption {
-            description = "A global list of paths to exclude. Supports glob.";
-            type = types.listOf types.str;
-            default = [ ];
-            example = [ "node_modules/*" ];
-          };
+        excludes = mkOption {
+          description = "A global list of paths to exclude. Supports glob.";
+          type = types.listOf types.str;
+          default = [ ];
+          example = [ "node_modules/*" ];
+        };
 
-          on-unmatched = mkOption {
-            description = "Log paths that did not match any formatters at the specified log level.";
-            type = types.enum [
+        on-unmatched = mkOption {
+          description = "Log paths that did not match any formatters at the specified log level.";
+          type = types.nullOr (
+            types.enum [
               "debug"
               "info"
               "warn"
               "error"
               "fatal"
-            ];
-            default = "warn";
-          };
+            ]
+          );
+          default = null;
         };
 
         formatter = mkOption {
@@ -87,7 +102,7 @@ let
         };
       };
       config = {
-        global.excludes = lib.mkIf config.enableDefaultExcludes [
+        excludes = lib.mkIf config.enableDefaultExcludes [
           # generated lock files i.e. yarn, cargo, nix flakes
           "*.lock"
           # Files generated by patch
@@ -327,7 +342,7 @@ in
 
   # Config
   config.build = {
-    configFile = configFormat.generate "treefmt.toml" config.settings;
+    inherit configFile;
     devShell = pkgs.mkShell {
       nativeBuildInputs = [ config.build.wrapper ] ++ (lib.attrValues config.build.programs);
     };

treefmt.nix

@@ -1,7 +1,7 @@
 { pkgs, ... }:
 {
   projectRootFile = "treefmt.nix";
-  settings.global.excludes = [ "*.toml" ];
+  settings.excludes = [ "*.toml" ];
 
   programs.deadnix.enable = true;
   programs.deno.enable = pkgs.hostPlatform.system != "riscv64-linux";