Add migration to git ignore SwiftPM build directories (#152766)

Opening a Swift package in Xcode generates `.build` and `.swiftpm` directories. These should be ignored as they contain intermediary build artifacts that aren't meant to be checked-in.

Part of https://github.com/flutter/flutter/issues/148018

packages/flutter_tools/lib/src/ios/mac.dart

@@ -24,6 +24,7 @@ import '../globals.dart' as globals;
 import '../macos/cocoapod_utils.dart';
 import '../macos/swift_package_manager.dart';
 import '../macos/xcode.dart';
+import '../migrations/swift_package_manager_gitignore_migration.dart';
 import '../migrations/swift_package_manager_integration_migration.dart';
 import '../migrations/xcode_project_object_version_migration.dart';
 import '../migrations/xcode_script_build_phase_migration.dart';
@@ -175,6 +176,7 @@ Future<XcodeBuildResult> buildXcodeProject({
         fileSystem: globals.fs,
         plistParser: globals.plistParser,
       ),
+      SwiftPackageManagerGitignoreMigration(project, globals.logger),
   ];
 
   final ProjectMigration migration = ProjectMigration(migrators);

packages/flutter_tools/lib/src/macos/build_macos.dart

@@ -16,6 +16,7 @@ import '../convert.dart';
 import '../globals.dart' as globals;
 import '../ios/xcode_build_settings.dart';
 import '../ios/xcodeproj.dart';
+import '../migrations/swift_package_manager_gitignore_migration.dart';
 import '../migrations/swift_package_manager_integration_migration.dart';
 import '../migrations/xcode_project_object_version_migration.dart';
 import '../migrations/xcode_script_build_phase_migration.dart';
@@ -100,6 +101,7 @@ Future<void> buildMacOS({
         fileSystem: globals.fs,
         plistParser: globals.plistParser,
       ),
+      SwiftPackageManagerGitignoreMigration(flutterProject, globals.logger),
   ];
 
   final ProjectMigration migration = ProjectMigration(migrators);

packages/flutter_tools/lib/src/migrations/swift_package_manager_gitignore_migration.dart

@@ -0,0 +1,63 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import '../base/file_system.dart';
+import '../base/project_migrator.dart';
+import '../project.dart';
+
+const String _gitignoreBefore = '''
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+migrate_working_dir/
+''';
+
+const String _gitignoreAfter = '''
+.DS_Store
+.atom/
+.build/
+.buildlog/
+.history
+.svn/
+.swiftpm/
+migrate_working_dir/
+''';
+
+/// Adds `.build/` and `.swiftpm/` to the .gitignore file.
+class SwiftPackageManagerGitignoreMigration extends ProjectMigrator {
+  SwiftPackageManagerGitignoreMigration(FlutterProject project, super.logger)
+      : _gitignoreFile = project.gitignoreFile;
+
+  final File _gitignoreFile;
+
+  @override
+  Future<void> migrate() async {
+    if (!_gitignoreFile.existsSync()) {
+      logger.printTrace(
+        '.gitignore file not found, skipping Swift Package Manager .gitignore migration.',
+      );
+      return;
+    }
+
+    final String originalContent = _gitignoreFile.readAsStringSync();
+
+    // Skip if .gitignore is already migrated.
+    if (originalContent.contains('.build/') && originalContent.contains('.swiftpm/')) {
+      return;
+    }
+
+    final String newContent = originalContent.replaceFirst(
+      _gitignoreBefore,
+      _gitignoreAfter,
+    );
+    if (newContent != originalContent) {
+      logger.printWarning(
+        '.gitignore does not ignore Swift Package Manager build directories, updating.',
+      );
+      _gitignoreFile.writeAsStringSync(newContent);
+    }
+  }
+}

packages/flutter_tools/lib/src/project.dart

@@ -233,6 +233,9 @@ class FlutterProject {
   /// which contains the dependencies each plugin depends on.
   File get flutterPluginsDependenciesFile => directory.childFile('.flutter-plugins-dependencies');
 
+  /// The `.gitignore` file of this project.
+  File get gitignoreFile => directory.childFile('.gitignore');
+
   /// The `.dart-tool` directory of this project.
   Directory get dartTool => directory.childDirectory('.dart_tool');
 

packages/flutter_tools/templates/app_shared/.gitignore.tmpl

@@ -5,9 +5,11 @@
 *.swp
 .DS_Store
 .atom/
+.build/
 .buildlog/
 .history
 .svn/
+.swiftpm/
 migrate_working_dir/
 
 # IntelliJ related

packages/flutter_tools/templates/plugin_shared/.gitignore.tmpl

@@ -5,9 +5,11 @@
 *.swp
 .DS_Store
 .atom/
+.build/
 .buildlog/
 .history
 .svn/
+.swiftpm/
 migrate_working_dir/
 
 # IntelliJ related

packages/flutter_tools/test/general.shard/migrations/swift_package_manager_gitignore_migration_test.dart

@@ -0,0 +1,132 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:file/file.dart';
+import 'package:file/memory.dart';
+import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/base/terminal.dart';
+import 'package:flutter_tools/src/migrations/swift_package_manager_gitignore_migration.dart';
+
+import 'package:flutter_tools/src/project.dart';
+import 'package:test/fake.dart';
+
+import '../../src/common.dart';
+
+void main() {
+  group('Swift Package Manager .gitignore migration', () {
+    late MemoryFileSystem memoryFileSystem;
+    late BufferLogger testLogger;
+    late FakeFlutterProject mockProject;
+    late File gitignoreFile;
+
+    setUp(() {
+      memoryFileSystem = MemoryFileSystem.test();
+      gitignoreFile = memoryFileSystem.file('.gitignore');
+
+      testLogger = BufferLogger(
+        terminal: Terminal.test(),
+        outputPreferences: OutputPreferences.test(),
+      );
+
+      mockProject = FakeFlutterProject(fileSystem: memoryFileSystem);
+    });
+
+    testWithoutContext('skipped if .gitignore file is missing', () {
+      final SwiftPackageManagerGitignoreMigration migration = SwiftPackageManagerGitignoreMigration(
+        mockProject,
+        testLogger,
+      );
+      migration.migrate();
+      expect(gitignoreFile.existsSync(), isFalse);
+
+      expect(
+        testLogger.traceText,
+        contains('.gitignore file not found, skipping Swift Package Manager .gitignore migration.'),
+      );
+      expect(testLogger.warningText, isEmpty);
+    });
+
+    testWithoutContext('skipped if nothing to migrate', () {
+      const String gitignoreFileContents = 'Nothing to migrate';
+
+      gitignoreFile.writeAsStringSync(gitignoreFileContents);
+
+      final DateTime updatedAt = gitignoreFile.lastModifiedSync();
+
+      final SwiftPackageManagerGitignoreMigration migration = SwiftPackageManagerGitignoreMigration(
+        mockProject,
+        testLogger,
+      );
+      migration.migrate();
+
+      expect(gitignoreFile.lastModifiedSync(), updatedAt);
+      expect(gitignoreFile.readAsStringSync(), gitignoreFileContents);
+      expect(testLogger.warningText, isEmpty);
+    });
+
+    testWithoutContext('skipped if already migrated', () {
+      const String gitignoreFileContents = '''
+.build/
+.swiftpm/
+''';
+
+      gitignoreFile.writeAsStringSync(gitignoreFileContents);
+
+      final DateTime updatedAt = gitignoreFile.lastModifiedSync();
+
+      final SwiftPackageManagerGitignoreMigration migration = SwiftPackageManagerGitignoreMigration(
+        mockProject,
+        testLogger,
+      );
+      migration.migrate();
+
+      expect(gitignoreFile.lastModifiedSync(), updatedAt);
+      expect(gitignoreFile.readAsStringSync(), gitignoreFileContents);
+      expect(testLogger.warningText, isEmpty);
+    });
+
+    testWithoutContext('migrates project to ignore Swift Package Manager build directories', () {
+      gitignoreFile.writeAsStringSync(
+        '.DS_Store\n'
+        '.atom/\n'
+        '.buildlog/\n'
+        '.history\n'
+        '.svn/\n'
+        'migrate_working_dir/\n'
+      );
+
+      final SwiftPackageManagerGitignoreMigration migration = SwiftPackageManagerGitignoreMigration(
+        mockProject,
+        testLogger,
+      );
+      migration.migrate();
+
+      expect(
+        gitignoreFile.readAsStringSync(),
+        '.DS_Store\n'
+        '.atom/\n'
+        '.build/\n'
+        '.buildlog/\n'
+        '.history\n'
+        '.svn/\n'
+        '.swiftpm/\n'
+        'migrate_working_dir/\n'
+      );
+
+      expect(
+        testLogger.warningText,
+        contains('.gitignore does not ignore Swift Package Manager build directories, updating.'),
+      );
+    });
+  });
+}
+
+class FakeFlutterProject extends Fake implements FlutterProject {
+  FakeFlutterProject({
+    required MemoryFileSystem fileSystem,
+  }) : gitignoreFile = fileSystem.file('.gitignore');
+
+  @override
+  File gitignoreFile;
+}