Enable Proguard by default on release mode (#39986)

packages/flutter_tools/gradle/flutter.gradle

@@ -132,16 +132,6 @@ class FlutterPlugin implements Plugin<Project> {
             }
         }
 
-        // Add custom build types
-        project.android.buildTypes {
-            profile {
-                initWith debug
-                if (it.hasProperty('matchingFallbacks')) {
-                    matchingFallbacks = ['debug', 'release']
-                }
-            }
-        }
-
         String flutterRootPath = resolveProperty(project, "flutter.sdk", System.env.FLUTTER_ROOT)
         if (flutterRootPath == null) {
             throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file or with a FLUTTER_ROOT environment variable.")
@@ -154,6 +144,30 @@ class FlutterPlugin implements Plugin<Project> {
         String flutterExecutableName = Os.isFamily(Os.FAMILY_WINDOWS) ? "flutter.bat" : "flutter"
         flutterExecutable = Paths.get(flutterRoot.absolutePath, "bin", flutterExecutableName).toFile();
 
+        // Add custom build types.
+        project.android.buildTypes {
+            profile {
+                initWith debug
+                if (it.hasProperty("matchingFallbacks")) {
+                    matchingFallbacks = ["debug", "release"]
+                }
+            }
+        }
+
+        if (useProguard(project)) {
+            String flutterProguardRules = Paths.get(flutterRoot.absolutePath, "packages", "flutter_tools",
+                    "gradle", "flutter_proguard_rules.pro")
+            project.android.buildTypes {
+                release {
+                    minifyEnabled true
+                    useProguard true
+                    // Fallback to `android/app/proguard-rules.pro`.
+                    // This way, custom Proguard rules can be configured as needed.
+                    proguardFiles project.android.getDefaultProguardFile("proguard-android.txt"), flutterProguardRules, "proguard-rules.pro"
+                }
+            }
+        }
+
         if (useLocalEngine(project)) {
             String engineOutPath = project.property('localEngineOut')
             File engineOut = project.file(engineOutPath)
@@ -375,6 +389,14 @@ class FlutterPlugin implements Plugin<Project> {
         return false
     }
 
+
+    private static Boolean useProguard(Project project) {
+        if (project.hasProperty('proguard')) {
+            return project.property('proguard').toBoolean()
+        }
+        return false
+    }
+
     private static Boolean buildPluginAsAar() {
         return System.getProperty('build-plugins-as-aars') == 'true'
     }

packages/flutter_tools/gradle/flutter_proguard_rules.pro

+# Prevents `Fragment and FragmentActivity not found`.
+# TODO(blasten): Remove once we bring the Maven dependencies.
+-dontwarn io.flutter.embedding.**
+
+# Build the ephemeral app in a module project.
+# Prevents: Warning: library class <plugin-package> depends on program class io.flutter.plugin.**
+# This is due to plugins (libraries) depending on the embedding (the program jar)
+-dontwarn io.flutter.plugin.**
+
+# The android.** package is provided by the OS at runtime.
+-dontwarn android.**

packages/flutter_tools/lib/src/build_info.dart

@@ -92,6 +92,7 @@ class AndroidBuildInfo {
       AndroidArch.arm64_v8a,
     ],
     this.splitPerAbi = false,
+    this.proguard = false,
   });
 
   // The build info containing the mode and flavor.
@@ -104,6 +105,9 @@ class AndroidBuildInfo {
   /// will be produced.
   final bool splitPerAbi;
 
+  /// Whether to enable Proguard on release mode.
+  final bool proguard;
+
   /// The target platforms for the build.
   final Iterable<AndroidArch> targetArchs;
 }

packages/flutter_tools/lib/src/commands/build_apk.dart

@@ -25,9 +25,15 @@ class BuildApkCommand extends BuildSubCommand {
     argParser
       ..addFlag('split-per-abi',
         negatable: false,
-        help: 'Whether to split the APKs per ABIs.'
+        help: 'Whether to split the APKs per ABIs. '
               'To learn more, see: https://developer.android.com/studio/build/configure-apk-splits#configure-abi-split',
       )
+      ..addFlag('proguard',
+        negatable: true,
+        defaultsTo: true,
+        help: 'Whether to enable Proguard on release mode. '
+              'To learn more, see: https://flutter.dev/docs/deployment/android#enabling-proguard',
+      )
       ..addMultiOption('target-platform',
         splitCommas: true,
         defaultsTo: <String>['android-arm', 'android-arm64'],
@@ -79,7 +85,8 @@ class BuildApkCommand extends BuildSubCommand {
     final BuildInfo buildInfo = getBuildInfo();
     final AndroidBuildInfo androidBuildInfo = AndroidBuildInfo(buildInfo,
       splitPerAbi: argResults['split-per-abi'],
-      targetArchs: argResults['target-platform'].map<AndroidArch>(getAndroidArchForName)
+      targetArchs: argResults['target-platform'].map<AndroidArch>(getAndroidArchForName),
+      proguard: argResults['proguard'],
     );
 
     if (buildInfo.isRelease && !androidBuildInfo.splitPerAbi && androidBuildInfo.targetArchs.length > 1) {

packages/flutter_tools/lib/src/commands/build_appbundle.dart

@@ -22,6 +22,12 @@ class BuildAppBundleCommand extends BuildSubCommand {
 
     argParser
       ..addFlag('track-widget-creation', negatable: false, hide: !verboseHelp)
+      ..addFlag('proguard',
+        negatable: true,
+        defaultsTo: true,
+        help: 'Whether to enable Proguard on release mode. '
+              'To learn more, see: https://flutter.dev/docs/deployment/android#enabling-proguard',
+      )
       ..addMultiOption('target-platform',
         splitCommas: true,
         defaultsTo: <String>['android-arm', 'android-arm64'],
@@ -63,7 +69,8 @@ class BuildAppBundleCommand extends BuildSubCommand {
   @override
   Future<FlutterCommandResult> runCommand() async {
     final AndroidBuildInfo androidBuildInfo = AndroidBuildInfo(getBuildInfo(),
-      targetArchs: argResults['target-platform'].map<AndroidArch>(getAndroidArchForName)
+      targetArchs: argResults['target-platform'].map<AndroidArch>(getAndroidArchForName),
+      proguard: argResults['proguard'],
     );
     await androidBuilder.buildAab(
       project: FlutterProject.current(),

packages/flutter_tools/lib/src/context_runner.dart

@@ -7,6 +7,7 @@ import 'dart:async';
 import 'android/android_sdk.dart';
 import 'android/android_studio.dart';
 import 'android/android_workflow.dart';
+import 'android/gradle.dart';
 import 'application_package.dart';
 import 'artifacts.dart';
 import 'asset.dart';
@@ -89,6 +90,7 @@ Future<T> runInContext<T>(
       FuchsiaSdk: () => FuchsiaSdk(),
       FuchsiaWorkflow: () => FuchsiaWorkflow(),
       GenSnapshot: () => const GenSnapshot(),
+      GradleUtils: () => GradleUtils(),
       HotRunnerConfig: () => HotRunnerConfig(),
       IMobileDevice: () => IMobileDevice(),
       IOSDeploy: () => const IOSDeploy(),

packages/flutter_tools/test/general.shard/channel_test.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:convert';
 import 'dart:io' hide File;
 
 import 'package:args/command_runner.dart';
@@ -17,21 +16,7 @@ import 'package:process/process.dart';
 
 import '../src/common.dart';
 import '../src/context.dart';
-
-Process createMockProcess({ int exitCode = 0, String stdout = '', String stderr = '' }) {
-  final Stream<List<int>> stdoutStream = Stream<List<int>>.fromIterable(<List<int>>[
-    utf8.encode(stdout),
-  ]);
-  final Stream<List<int>> stderrStream = Stream<List<int>>.fromIterable(<List<int>>[
-    utf8.encode(stderr),
-  ]);
-  final Process process = MockProcess();
-
-  when(process.stdout).thenAnswer((_) => stdoutStream);
-  when(process.stderr).thenAnswer((_) => stderrStream);
-  when(process.exitCode).thenAnswer((_) => Future<int>.value(exitCode));
-  return process;
-}
+import '../src/mocks.dart';
 
 void main() {
   group('channel', () {

packages/flutter_tools/test/general.shard/commands/upgrade_test.dart

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:convert';
-
 import 'package:flutter_tools/src/base/common.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/io.dart';
@@ -17,21 +15,7 @@ import 'package:process/process.dart';
 
 import '../../src/common.dart';
 import '../../src/context.dart';
-
-Process createMockProcess({ int exitCode = 0, String stdout = '', String stderr = '' }) {
-  final Stream<List<int>> stdoutStream = Stream<List<int>>.fromIterable(<List<int>>[
-    utf8.encode(stdout),
-  ]);
-  final Stream<List<int>> stderrStream = Stream<List<int>>.fromIterable(<List<int>>[
-    utf8.encode(stderr),
-  ]);
-  final Process process = MockProcess();
-
-  when(process.stdout).thenAnswer((_) => stdoutStream);
-  when(process.stderr).thenAnswer((_) => stderrStream);
-  when(process.exitCode).thenAnswer((_) => Future<int>.value(exitCode));
-  return process;
-}
+import '../../src/mocks.dart';
 
 void main() {
   group('UpgradeCommandRunner', () {

packages/flutter_tools/test/src/common.dart

@@ -116,6 +116,8 @@ Future<String> createProject(Directory temp, { List<String> arguments }) async {
   final CreateCommand command = CreateCommand();
   final CommandRunner<void> runner = createTestCommandRunner(command);
   await runner.run(<String>['create', ...arguments, projectPath]);
+  // Created `.packages` since it's not created when the flag `--no-pub` is passed.
+  fs.file(fs.path.join(projectPath, '.packages')).createSync();
   return projectPath;
 }
 

packages/flutter_tools/test/src/mocks.dart

@@ -221,6 +221,24 @@ ProcessFactory flakyProcessFactory({
   };
 }
 
+/// Creates a mock process that returns with the given [exitCode], [stdout] and [stderr].
+Process createMockProcess({ int exitCode = 0, String stdout = '', String stderr = '' }) {
+  final Stream<List<int>> stdoutStream = Stream<List<int>>.fromIterable(<List<int>>[
+    utf8.encode(stdout),
+  ]);
+  final Stream<List<int>> stderrStream = Stream<List<int>>.fromIterable(<List<int>>[
+    utf8.encode(stderr),
+  ]);
+  final Process process = MockBasicProcess();
+
+  when(process.stdout).thenAnswer((_) => stdoutStream);
+  when(process.stderr).thenAnswer((_) => stderrStream);
+  when(process.exitCode).thenAnswer((_) => Future<int>.value(exitCode));
+  return process;
+}
+
+class MockBasicProcess extends Mock implements Process {}
+
 /// A process that exits successfully with no output and ignores all input.
 class MockProcess extends Mock implements Process {
   MockProcess({