Add builder for messages

pkgs/messages/example_json/hook/build.dart

@@ -2,40 +2,16 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'dart:io';
-
+import 'package:messages/messages_build.dart';
 import 'package:native_assets_cli/native_assets_cli.dart';
 
-const package = 'example_json';
 void main(List<String> args) {
-  final dir = 'lib/';
   build(args, (config, output) async {
-    getArbs(config, output, dir, [
-      'testarb',
-      'testarbctx2',
-      'testarbctx2_fr',
-    ]);
-  });
-}
+    final builder = MessageBuilder(
+      arbFiles: ['lib/testarb.arb', 'lib/testarbctx2.arb'],
+      locales: ['en', 'de', 'fr'],
+    );
 
-void getArbs(
-  BuildConfig config,
-  BuildOutput output,
-  String dir,
-  List<String> assets,
-) {
-  output.addAssets(assets.map((asset) => getArb(config, dir, asset)));
-  output.addDependencies([
-    config.packageRoot.resolve('hook/build.dart'),
-  ]);
-}
-
-DataAsset getArb(BuildConfig config, String dir, String name) {
-  final directory = Directory(dir);
-  final resolved = directory.uri.resolve('$name.json');
-  return DataAsset(
-    package: package,
-    name: resolved.path,
-    file: config.packageRoot.resolveUri(resolved),
-  );
+    await builder.run(config: config, output: output, logger: null);
+  });
 }

pkgs/messages/lib/messages_build.dart

@@ -0,0 +1,51 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+
+import 'package:logging/logging.dart';
+import 'package:native_assets_cli/native_assets_cli.dart';
+import 'package:path/path.dart' as p;
+
+// implements Builder
+class MessageBuilder {
+  final List<String> arbFiles;
+  final List<String> locales;
+
+  MessageBuilder({
+    required this.arbFiles,
+    required this.locales,
+  });
+
+  Future<void> run({
+    required BuildConfig config,
+    required BuildOutput output,
+    required Logger? logger,
+  }) async {
+    DataAsset fileToAsset(String relativePath) => DataAsset(
+          package: config.packageName,
+          name: relativePath,
+          file: config.packageRoot.resolve(relativePath),
+        );
+
+    for (final arb in arbFiles) {
+      final arbNoExtension = p.withoutExtension(arb);
+      for (final locale in locales) {
+        final data = p.setExtension(arbNoExtension, '_$locale.json');
+        final asset = fileToAsset(data);
+        if (await File.fromUri(asset.file!).exists()) {
+          output.addAsset(asset);
+        } else {
+          logger?.warning('Could not find messages for locale "$locale" and'
+              ' arb "$arb" at ${asset.file}');
+        }
+      }
+    }
+
+    output.addDependencies([
+      ...arbFiles,
+      'hook/build.dart',
+    ].map(config.packageRoot.resolve));
+  }
+}

pkgs/messages/pubspec.yaml

@@ -9,6 +9,9 @@ environment:
 dependencies:
   collection: ^1.17.1
   intl: ^0.18.0
+  logging: ^1.2.0
+  native_assets_cli: ^0.6.0
+  path: ^1.9.0
 
 dev_dependencies:
   dart_flutter_team_lints: ^2.1.1