feat(shorebird_cli): add shorebird build aar command (#570)

packages/shorebird_cli/lib/src/commands/build/build.dart

@@ -1,3 +1,4 @@
+export 'build_aar_command.dart';
 export 'build_apk_command.dart';
 export 'build_app_bundle_command.dart';
 export 'build_command.dart';

packages/shorebird_cli/lib/src/commands/build/build_aar_command.dart

@@ -0,0 +1,99 @@
+import 'dart:async';
+import 'dart:io';
+
+import 'package:mason_logger/mason_logger.dart';
+import 'package:path/path.dart' as p;
+import 'package:shorebird_cli/src/auth_logger_mixin.dart';
+import 'package:shorebird_cli/src/command.dart';
+import 'package:shorebird_cli/src/shorebird_build_mixin.dart';
+import 'package:shorebird_cli/src/shorebird_config_mixin.dart';
+import 'package:shorebird_cli/src/shorebird_validation_mixin.dart';
+
+/// {@template build_aar_command}
+///
+/// `shorebird build aar`
+/// Build an Android aar file from your app.
+/// {@endtemplate}
+class BuildAarCommand extends ShorebirdCommand
+    with
+        AuthLoggerMixin,
+        ShorebirdValidationMixin,
+        ShorebirdConfigMixin,
+        ShorebirdBuildMixin {
+  BuildAarCommand({
+    required super.logger,
+    super.auth,
+  }) {
+    // We would have a "target" option here, similar to what [BuildApkCommand]
+    // and [BuildAabCommand] have, but target cannot currently be configured in
+    // `flutter build aar` and is always assumed to be lib/main.dart.
+    argParser
+      ..addOption(
+        'flavor',
+        help: 'The product flavor to use when building the app.',
+      )
+      // `flutter build aar` defaults to a build number of 1.0, so we do the
+      // same.
+      ..addOption(
+        'build-number',
+        help: 'The build number of the aar',
+        defaultsTo: '1.0',
+      );
+  }
+
+  @override
+  String get name => 'aar';
+
+  @override
+  String get description => 'Build an Android AAR file from your module.';
+
+  @override
+  Future<int> run() async {
+    if (!auth.isAuthenticated) {
+      printNeedsAuthInstructions();
+      return ExitCode.noUser.code;
+    }
+
+    final pubspec = getPubspecYaml();
+    if (pubspec == null) {
+      logger.err('No pubspec.yaml file found.');
+      return ExitCode.config.code;
+    }
+
+    final module = pubspec.flutter?['module'] as Map?;
+    final androidPackageName = module?['androidPackage'] as String?;
+    if (androidPackageName == null) {
+      logger.err('Could not find androidPackage in pubspec.yaml.');
+      return ExitCode.config.code;
+    }
+
+    final flavor = results['flavor'] as String?;
+    final buildNumber = results['build-number'] as String;
+    final buildProgress = logger.progress('Building aar');
+    try {
+      await buildAar(buildNumber: buildNumber, flavor: flavor);
+    } on ProcessException catch (error) {
+      buildProgress.fail('Failed to build: ${error.message}');
+      return ExitCode.software.code;
+    }
+
+    buildProgress.complete();
+
+    final aarPath = p.joinAll([
+      'build',
+      'host',
+      'outputs',
+      'repo',
+      ...androidPackageName.split('.'),
+      'flutter_release',
+      buildNumber,
+      'flutter_release-$buildNumber.aar',
+    ]);
+
+    logger.info('''
+📦 Generated an aar at:
+${lightCyan.wrap(aarPath)}''');
+
+    return ExitCode.success.code;
+  }
+}

packages/shorebird_cli/lib/src/commands/build/build_command.dart

@@ -8,6 +8,7 @@ import 'package:shorebird_cli/src/commands/build/build.dart';
 class BuildCommand extends ShorebirdCommand {
   /// {@macro build_command}
   BuildCommand({required super.logger}) {
+    addSubcommand(BuildAarCommand(logger: logger));
     addSubcommand(BuildApkCommand(logger: logger));
     addSubcommand(BuildAppBundleCommand(logger: logger));
     addSubcommand(BuildIpaCommand(logger: logger));

packages/shorebird_cli/lib/src/shorebird_build_mixin.dart

@@ -93,6 +93,37 @@ mixin ShorebirdBuildMixin on ShorebirdCommand {
     }
   }
 
+  Future<void> buildAar({
+    required String buildNumber,
+    String? flavor,
+  }) async {
+    const executable = 'flutter';
+    final arguments = [
+      'build',
+      'aar',
+      '--no-debug',
+      '--no-profile',
+      '--build-number=$buildNumber',
+      if (flavor != null) '--flavor=$flavor',
+      ...results.rest,
+    ];
+
+    final result = await process.run(
+      executable,
+      arguments,
+      runInShell: true,
+    );
+
+    if (result.exitCode != ExitCode.success.code) {
+      throw ProcessException(
+        'flutter',
+        arguments,
+        result.stderr.toString(),
+        result.exitCode,
+      );
+    }
+  }
+
   Future<void> buildApk({String? flavor, String? target}) async {
     const executable = 'flutter';
     final arguments = [