Migrator for android 35/16kb page size cmake flags for plugin_ffi (#156221)

Migrates existing instantions of `--template plugin_ffi` to deal with Android 15 16kb memory pages.

Issue:

* https://github.com/flutter/flutter/issues/155933

@reidbaker I could only find migrations that run from the root application. However the file needing to be migrated is a plugin. The plugin is being referenced from the example in the example dir and that's where the migrator is run, so I wrote the code so that it walks up to find the plugin. Do you know of a way to run migrators to non-root projects? (Can we even safely do so, e.g. the non-root could be in the pub cache, could be a different project on the users' system etc. So maybe checking if we are in the examples dir is the only sane thing to do?)

Tests:

* Added unit tests in `test/general.shard/android/migrations/cmake_android_16k_pages_migration_test.dart`

packages/flutter_tools/lib/src/android/gradle.dart

@@ -35,6 +35,7 @@ import 'gradle_errors.dart';
 import 'gradle_utils.dart';
 import 'java.dart';
 import 'migrations/android_studio_java_gradle_conflict_migration.dart';
+import 'migrations/cmake_android_16k_pages_migration.dart';
 import 'migrations/min_sdk_version_migration.dart';
 import 'migrations/multidex_removal_migration.dart';
 import 'migrations/top_level_gradle_build_file_migration.dart';
@@ -311,6 +312,7 @@ class AndroidGradleBuilder implements AndroidBuilder {
           java: globals.java),
       MinSdkVersionMigration(project.android, _logger),
       MultidexRemovalMigration(project.android, _logger),
+      CmakeAndroid16kPagesMigration(project.android, _logger),
     ];
 
     final ProjectMigration migration = ProjectMigration(migrators);

packages/flutter_tools/lib/src/android/migrations/cmake_android_16k_pages_migration.dart

@@ -0,0 +1,74 @@
+// 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';
+
+/// Adds the snippet to the CMake file to compile for Android 15.
+///
+/// Location of CMakeLists.txt is the src/CMakeLists.txt in the plugin
+/// created with --template plugin_ffi.
+///
+/// ```cmake
+/// if (ANDROID)
+///   # Support Android 15 16k page size.
+///   target_link_options({{projectName}} PRIVATE "-Wl,-z,max-page-size=16384")
+/// endif()
+/// ```
+class CmakeAndroid16kPagesMigration extends ProjectMigrator {
+  CmakeAndroid16kPagesMigration(AndroidProject project, super.logger)
+      : _project = project;
+
+  final AndroidProject _project;
+
+  @override
+  Future<void> migrate() async {
+    // If the migrator is run in the example directory, navigate to the
+    // plugin directory which contains src/CMakeLists.txt.
+    final File cmakeLists = _project.parent.directory.parent
+        .childDirectory('src/')
+        .childFile('CMakeLists.txt');
+
+    if (!cmakeLists.existsSync()) {
+      logger.printTrace(
+          'CMake project not found, skipping support Android 15 16k page size migration.');
+      return;
+    }
+
+    final String original = cmakeLists.readAsStringSync();
+
+    if (original.contains('-Wl,-z,max-page-size=16384')) {
+      // Link flags already present.
+      return;
+    }
+
+    final RegExp regex =
+        RegExp(r'target_compile_definitions\(([^ ]*) PUBLIC DART_SHARED_LIB\)');
+    final String? projectName = regex.firstMatch(original)?.group(1);
+    const String before = '''
+ PUBLIC DART_SHARED_LIB)
+''';
+
+    /// Relevant template: templates/plugin_ffi/src.tmpl/CMakeLists.txt.tmpl
+    final String linkerFlags = '''
+
+if (ANDROID)
+  # Support Android 15 16k page size.
+  target_link_options($projectName PRIVATE "-Wl,-z,max-page-size=16384")
+endif()
+''';
+
+    final String updated = original.replaceFirst(
+      before,
+      '$before$linkerFlags',
+    );
+
+    if (original != updated) {
+      logger.printStatus(
+          'CMake missing support Android 15 16k page size, updating.');
+      cmakeLists.writeAsStringSync(updated);
+    }
+  }
+}

packages/flutter_tools/templates/plugin_ffi/src.tmpl/CMakeLists.txt.tmpl

@@ -16,7 +16,7 @@ set_target_properties({{projectName}} PROPERTIES
 
 target_compile_definitions({{projectName}} PUBLIC DART_SHARED_LIB)
 
-if(ANDROID)
+if (ANDROID)
   # Support Android 15 16k page size
   target_link_options({{projectName}} PRIVATE "-Wl,-z,max-page-size=16384")
 endif()

packages/flutter_tools/test/commands.shard/permeable/create_test.dart

@@ -3202,6 +3202,9 @@ void main() {
     expect(cmakeLists.existsSync(), true);
 
     final String cmakeListsContent = await cmakeLists.readAsString();
+    // If we ever change the flags, this should be accounted for in the
+    // migration as well:
+    // lib/src/android/migrations/cmake_android_16k_pages_migration.dart
     const String expected16KbFlags = 'PRIVATE "-Wl,-z,max-page-size=16384")';
     expect(cmakeListsContent, contains(expected16KbFlags));
   });

packages/flutter_tools/test/general.shard/android/migration/cmake_android_16k_pages_migration_test.dart

@@ -0,0 +1,136 @@
+// 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/android/migrations/cmake_android_16k_pages_migration.dart';
+import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/project.dart';
+import 'package:test/fake.dart';
+
+import '../../../src/common.dart';
+
+const String _sampleCmakeListsTxtUnmigrated = r'''
+# The Flutter tooling requires that developers have CMake 3.10 or later
+# installed. You should not increase this version, as doing so will cause
+# the plugin to fail to compile for some customers of the plugin.
+cmake_minimum_required(VERSION 3.10)
+
+project(my_plugin_library VERSION 0.0.1 LANGUAGES C)
+
+add_library(my_plugin SHARED
+  "my_plugin.c"
+)
+
+set_target_properties(my_plugin PROPERTIES
+  PUBLIC_HEADER my_plugin.h
+  OUTPUT_NAME "my_plugin"
+)
+
+target_compile_definitions(my_plugin PUBLIC DART_SHARED_LIB)
+''';
+
+const String _sampleCmakeListsTxtMigrated = r'''
+# The Flutter tooling requires that developers have CMake 3.10 or later
+# installed. You should not increase this version, as doing so will cause
+# the plugin to fail to compile for some customers of the plugin.
+cmake_minimum_required(VERSION 3.10)
+
+project(my_plugin_library VERSION 0.0.1 LANGUAGES C)
+
+add_library(my_plugin SHARED
+  "my_plugin.c"
+)
+
+set_target_properties(my_plugin PROPERTIES
+  PUBLIC_HEADER my_plugin.h
+  OUTPUT_NAME "my_plugin"
+)
+
+target_compile_definitions(my_plugin PUBLIC DART_SHARED_LIB)
+
+if (ANDROID)
+  # Support Android 15 16k page size.
+  target_link_options(my_plugin PRIVATE "-Wl,-z,max-page-size=16384")
+endif()
+''';
+
+void main() {
+  group('Android migration', () {
+    group('CMake file', () {
+      late MemoryFileSystem memoryFileSystem;
+      late File cmakeFile;
+      late BufferLogger bufferLogger;
+      late FakeAndroidProject project;
+      late CmakeAndroid16kPagesMigration migration;
+
+      setUp(() {
+        memoryFileSystem = MemoryFileSystem.test();
+        final Directory pluginDir = memoryFileSystem.currentDirectory;
+        final Directory exampleDir = pluginDir.childDirectory('example');
+        exampleDir.createSync();
+        final Directory androidDir = exampleDir.childDirectory('android');
+        androidDir.createSync();
+        final Directory srcDir = pluginDir.childDirectory('src');
+        srcDir.createSync();
+        cmakeFile = srcDir.childFile('CMakeLists.txt');
+        cmakeFile.writeAsString(_sampleCmakeListsTxtMigrated);
+
+        bufferLogger = BufferLogger.test();
+        project = FakeAndroidProject(
+          parent: FakeFlutterProject(
+            directory: exampleDir,
+          ),
+        );
+        migration = CmakeAndroid16kPagesMigration(project, bufferLogger);
+      });
+
+      testWithoutContext('do nothing when files missing', () async {
+        cmakeFile.deleteSync();
+        await migration.migrate();
+        expect(
+          bufferLogger.traceText,
+          contains(
+            'CMake project not found, skipping support Android 15 16k page size migration.',
+          ),
+        );
+      });
+
+      testWithoutContext('migrate', () async {
+        cmakeFile.writeAsStringSync(_sampleCmakeListsTxtUnmigrated);
+        await migration.migrate();
+        expect(
+          cmakeFile.readAsStringSync(),
+          _sampleCmakeListsTxtMigrated,
+        );
+      });
+
+      testWithoutContext('do nothing when already migrated', () async {
+        expect(
+          cmakeFile.readAsStringSync(),
+          _sampleCmakeListsTxtMigrated,
+        );
+        await migration.migrate();
+        expect(
+          cmakeFile.readAsStringSync(),
+          _sampleCmakeListsTxtMigrated,
+        );
+      });
+    });
+  });
+}
+
+class FakeAndroidProject extends Fake implements AndroidProject {
+  FakeAndroidProject({required this.parent});
+
+  @override
+  FlutterProject parent;
+}
+
+class FakeFlutterProject extends Fake implements FlutterProject {
+  FakeFlutterProject({required this.directory});
+
+  @override
+  final Directory directory;
+}