Integrate package:flutter_lints into templates (#81417)

packages/flutter_tools/templates/app/analysis_options.yaml.tmpl

+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  # The lint rules applied to this project can be customized in the
+  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
+  # included above or to enable additional rules. A list of all available lints
+  # and their documentation is published at
+  # https://dart-lang.github.io/linter/lints/index.html.
+  #
+  # Instead of disabling a lint rule for the entire project in the
+  # section below, it can also be suppressed for a single line of code
+  # or a specific dart file by using the `// ignore: name_of_lint` and
+  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
+  # producing the lint.
+  rules:
+    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
+    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

packages/flutter_tools/templates/app/lib/main.dart.tmpl

@@ -7,11 +7,13 @@ import 'package:{{pluginProjectName}}/{{pluginProjectName}}.dart';
 {{/withPluginHook}}
 
 void main() {
-  runApp(MyApp());
+  runApp(const MyApp());
 }
 
 {{^withPluginHook}}
 class MyApp extends StatelessWidget {
+  const MyApp({Key? key}) : super(key: key);
+
   // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
@@ -29,13 +31,13 @@ class MyApp extends StatelessWidget {
         // is not restarted.
         primarySwatch: Colors.blue,
       ),
-      home: MyHomePage(title: 'Flutter Demo Home Page'),
+      home: const MyHomePage(title: 'Flutter Demo Home Page'),
     );
   }
 }
 
 class MyHomePage extends StatefulWidget {
-  MyHomePage({Key? key, required this.title}) : super(key: key);
+  const MyHomePage({Key? key, required this.title}) : super(key: key);
 
   // This widget is the home page of your application. It is stateful, meaning
   // that it has a State object (defined below) that contains fields that affect
@@ -49,7 +51,7 @@ class MyHomePage extends StatefulWidget {
   final String title;
 
   @override
-  _MyHomePageState createState() => _MyHomePageState();
+  State<MyHomePage> createState() => _MyHomePageState();
 }
 
 class _MyHomePageState extends State<MyHomePage> {
@@ -100,7 +102,7 @@ class _MyHomePageState extends State<MyHomePage> {
           // horizontal).
           mainAxisAlignment: MainAxisAlignment.center,
           children: <Widget>[
-            Text(
+            const Text(
               'You have pushed the button this many times:',
             ),
             Text(
@@ -113,7 +115,7 @@ class _MyHomePageState extends State<MyHomePage> {
       floatingActionButton: FloatingActionButton(
         onPressed: _incrementCounter,
         tooltip: 'Increment',
-        child: Icon(Icons.add),
+        child: const Icon(Icons.add),
       ), // This trailing comma makes auto-formatting nicer for build methods.
     );
   }
@@ -121,8 +123,10 @@ class _MyHomePageState extends State<MyHomePage> {
 {{/withPluginHook}}
 {{#withPluginHook}}
 class MyApp extends StatefulWidget {
+  const MyApp({Key? key}) : super(key: key);
+
   @override
-  _MyAppState createState() => _MyAppState();
+  State<MyApp> createState() => _MyAppState();
 }
 
 class _MyAppState extends State<MyApp> {

packages/flutter_tools/templates/app/pubspec.yaml.tmpl

@@ -2,7 +2,7 @@ name: {{projectName}}
 description: {{description}}
 
 # The following line prevents the package from being accidentally published to
-# pub.dev using `pub publish`. This is preferred for private packages.
+# pub.dev using `flutter pub publish`. This is preferred for private packages.
 publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 {{^withPluginHook}}
 
@@ -22,6 +22,12 @@ version: 1.0.0+1
 environment:
   sdk: {{dartSdkVersionBounds}}
 
+# Dependencies specify other packages that your package needs in order to work.
+# To automatically upgrade your package dependencies to the latest versions
+# consider running `flutter pub upgrade --major-versions`. Alternatively,
+# dependencies can be manually updated by changing the version numbers below to
+# the latest version available on pub.dev. To see which dependencies have newer
+# versions available, run `flutter pub outdated`.
 dependencies:
   flutter:
     sdk: flutter
@@ -44,6 +50,13 @@ dev_dependencies:
   flutter_test:
     sdk: flutter
 
+  # The "flutter_lints" package below contains a set of recommended lints to
+  # encourage good coding practices. The lint set provided by the package is
+  # activated in the `analysis_options.yaml` file located at the root of your
+  # package. See that file for information about deactivating specific lint
+  # rules and activating additional ones.
+  flutter_lints: ^1.0.0-0
+
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec
 

packages/flutter_tools/templates/app/test/widget_test.dart.tmpl

@@ -14,7 +14,7 @@ import 'package:{{projectName}}/main.dart';
 void main() {
   testWidgets('Counter increments smoke test', (WidgetTester tester) async {
     // Build our app and trigger a frame.
-    await tester.pumpWidget(MyApp());
+    await tester.pumpWidget(const MyApp());
 
     // Verify that our counter starts at 0.
     expect(find.text('0'), findsOneWidget);
@@ -34,7 +34,7 @@ void main() {
 void main() {
   testWidgets('Verify Platform version', (WidgetTester tester) async {
     // Build our app and trigger a frame.
-    await tester.pumpWidget(MyApp());
+    await tester.pumpWidget(const MyApp());
 
     // Verify that platform version is retrieved.
     expect(

packages/flutter_tools/templates/module/common/analysis_options.yaml.tmpl

+include: package:flutter_lints/flutter.yaml
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

packages/flutter_tools/templates/module/common/lib/main.dart.tmpl

@@ -6,10 +6,12 @@ import 'package:flutter/services.dart';
 import 'package:{{pluginProjectName}}/{{pluginProjectName}}.dart';
 {{/withPluginHook}}
 
-void main() => runApp(MyApp());
+void main() => runApp(const MyApp());
 
 {{^withPluginHook}}
 class MyApp extends StatelessWidget {
+  const MyApp({Key? key}) : super(key: key);
+
   // This widget is the root of your application.
   @override
   Widget build(BuildContext context) {
@@ -26,13 +28,13 @@ class MyApp extends StatelessWidget {
         // counter didn't reset back to zero; the application is not restarted.
         primarySwatch: Colors.blue,
       ),
-      home: MyHomePage(title: 'Flutter Demo Home Page'),
+      home: const MyHomePage(title: 'Flutter Demo Home Page'),
     );
   }
 }
 
 class MyHomePage extends StatefulWidget {
-  MyHomePage({Key? key, required this.title}) : super(key: key);
+  const MyHomePage({Key? key, required this.title}) : super(key: key);
 
   // This widget is the home page of your application. It is stateful, meaning
   // that it has a State object (defined below) that contains fields that affect
@@ -46,7 +48,7 @@ class MyHomePage extends StatefulWidget {
   final String title;
 
   @override
-  _MyHomePageState createState() => _MyHomePageState();
+  State<MyHomePage> createState() => _MyHomePageState();
 }
 
 class _MyHomePageState extends State<MyHomePage> {
@@ -97,7 +99,7 @@ class _MyHomePageState extends State<MyHomePage> {
           // horizontal).
           mainAxisAlignment: MainAxisAlignment.center,
           children: <Widget>[
-            Text(
+            const Text(
               'You have pushed the button this many times:',
             ),
             Text(
@@ -110,7 +112,7 @@ class _MyHomePageState extends State<MyHomePage> {
       floatingActionButton: FloatingActionButton(
         onPressed: _incrementCounter,
         tooltip: 'Increment',
-        child: Icon(Icons.add),
+        child: const Icon(Icons.add),
       ), // This trailing comma makes auto-formatting nicer for build methods.
     );
   }
@@ -118,8 +120,10 @@ class _MyHomePageState extends State<MyHomePage> {
 {{/withPluginHook}}
 {{#withPluginHook}}
 class MyApp extends StatefulWidget {
+  const MyApp({Key? key}) : super(key: key);
+
   @override
-  _MyAppState createState() => _MyAppState();
+  State<MyApp> createState() => _MyAppState();
 }
 
 class _MyAppState extends State<MyApp> {

packages/flutter_tools/templates/module/common/pubspec.yaml.tmpl

@@ -31,6 +31,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  flutter_lints: ^1.0.0-0
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec

packages/flutter_tools/templates/module/common/test/widget_test.dart.tmpl

@@ -14,7 +14,7 @@ import 'package:{{projectName}}/main.dart';
 void main() {
   testWidgets('Counter increments smoke test', (WidgetTester tester) async {
     // Build our app and trigger a frame.
-    await tester.pumpWidget(MyApp());
+    await tester.pumpWidget(const MyApp());
 
     // Verify that our counter starts at 0.
     expect(find.text('0'), findsOneWidget);
@@ -34,7 +34,7 @@ void main() {
 void main() {
   testWidgets('Verify Platform version', (WidgetTester tester) async {
     // Build our app and trigger a frame.
-    await tester.pumpWidget(MyApp());
+    await tester.pumpWidget(const MyApp());
 
     // Verify that platform version is retrieved.
     expect(

packages/flutter_tools/templates/package/analysis_options.yaml.tmpl

+include: package:flutter_lints/flutter.yaml
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

packages/flutter_tools/templates/package/pubspec.yaml.tmpl

@@ -14,6 +14,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  flutter_lints: ^1.0.0-0
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec

packages/flutter_tools/templates/plugin/analysis_options.yaml.tmpl

+include: package:flutter_lints/flutter.yaml
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

packages/flutter_tools/templates/plugin/lib/projectName.dart.tmpl

@@ -10,8 +10,7 @@ import 'dart:async';
 import 'package:flutter/services.dart';
 
 class {{pluginDartClass}} {
-  static const MethodChannel _channel =
-      const MethodChannel('{{projectName}}');
+  static const MethodChannel _channel = MethodChannel('{{projectName}}');
 
   static Future<String?> get platformVersion async {
     final String? version = await _channel.invokeMethod('getPlatformVersion');

packages/flutter_tools/templates/plugin/pubspec.yaml.tmpl

@@ -18,6 +18,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  flutter_lints: ^1.0.0-0
 
 # For information on the generic Dart part of this file, see the
 # following page: https://dart.dev/tools/pub/pubspec

packages/flutter_tools/templates/template_manifest.json

@@ -33,6 +33,7 @@
         "templates/app/android.tmpl/gradle/wrapper/gradle-wrapper.properties",
         "templates/app/android.tmpl/gradle.properties.tmpl",
         "templates/app/android.tmpl/settings.gradle",
+        "templates/app/analysis_options.yaml.tmpl",
         "templates/app/ios-objc.tmpl/Runner/AppDelegate.h",
         "templates/app/ios-objc.tmpl/Runner/AppDelegate.m",
         "templates/app/ios-objc.tmpl/Runner/main.m",
@@ -170,6 +171,7 @@
         "templates/module/common/.idea/modules.xml.tmpl",
         "templates/module/common/.idea/workspace.xml.tmpl",
         "templates/module/common/.metadata.tmpl",
+        "templates/module/common/analysis_options.yaml.tmpl",
         "templates/module/common/lib/main.dart.tmpl",
         "templates/module/common/projectName.iml.tmpl",
         "templates/module/common/projectName_android.iml.tmpl",
@@ -229,6 +231,7 @@
         "templates/package/.idea/modules.xml.tmpl",
         "templates/package/.idea/workspace.xml.tmpl",
         "templates/package/.metadata.tmpl",
+        "templates/package/analysis_options.yaml.tmpl",
         "templates/package/CHANGELOG.md.tmpl",
         "templates/package/lib/projectName.dart.tmpl",
         "templates/package/LICENSE.tmpl",
@@ -242,6 +245,7 @@
         "templates/plugin/.idea/runConfigurations/example_lib_main_dart.xml.tmpl",
         "templates/plugin/.idea/workspace.xml.tmpl",
         "templates/plugin/.metadata.tmpl",
+        "templates/plugin/analysis_options.yaml.tmpl",
         "templates/plugin/android-java.tmpl/build.gradle.tmpl",
         "templates/plugin/android-java.tmpl/projectName_android.iml.tmpl",
         "templates/plugin/android-java.tmpl/src/main/java/androidIdentifier/pluginClass.java.tmpl",

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

@@ -90,6 +90,7 @@ void main() {
       projectDir,
       <String>['-i', 'objc', '-a', 'java'],
       <String>[
+        'analysis_options.yaml',
         'android/app/src/main/java/com/example/flutter_project/MainActivity.java',
         'android/app/src/main/java/io/flutter/plugins/GeneratedPluginRegistrant.java',
         'flutter_project.iml',
@@ -117,6 +118,7 @@ void main() {
       projectDir,
       <String>['-i', 'objc', '-a', 'java'],
       <String>[
+        'analysis_options.yaml',
         'android/app/src/main/java/com/example/flutter_project/MainActivity.java',
         'android/app/src/main/java/io/flutter/plugins/GeneratedPluginRegistrant.java',
         'flutter_project.iml',
@@ -146,6 +148,7 @@ void main() {
       '.ios/Flutter/flutter_project.podspec',
       '.ios/Flutter/engine/Flutter.podspec',
       '.metadata',
+      'analysis_options.yaml',
       'lib/main.dart',
       'pubspec.yaml',
       'README.md',
@@ -380,6 +383,7 @@ void main() {
       projectDir,
       <String>['--template=package'],
       <String>[
+        'analysis_options.yaml',
         'lib/flutter_project.dart',
         'test/flutter_project_test.dart',
       ],
@@ -417,6 +421,7 @@ void main() {
       projectDir,
       <String>['--template=plugin', '-i', 'objc', '-a', 'java'],
       <String>[
+        'analysis_options.yaml',
         'example/lib/main.dart',
         'flutter_project.iml',
         'lib/flutter_project.dart',
@@ -500,6 +505,7 @@ void main() {
       projectDir,
       <String>['--no-pub', '--template=plugin', '-a', 'kotlin', '--ios-language', 'swift', '--platforms', 'ios,android'],
       <String>[
+        'analysis_options.yaml',
         'android/src/main/kotlin/com/example/flutter_project/FlutterProjectPlugin.kt',
         'example/android/app/src/main/kotlin/com/example/flutter_project_example/MainActivity.kt',
         'example/ios/Runner/AppDelegate.swift',
@@ -592,6 +598,7 @@ void main() {
       '.gitignore',
       '.metadata',
       '.packages',
+      'analysis_options.yaml',
       'lib/main.dart',
       'pubspec.lock',
       'pubspec.yaml',
@@ -1691,7 +1698,7 @@ void main() {
         return FakeHttpClient.list(<FakeRequest>[
           FakeRequest(
             Uri.parse('https://master-api.flutter.dev/snippets/foo.bar.Baz.dart'),
-            response: FakeResponse(body: utf8.encode('void main() { String? foo; print(foo); }')),
+            response: FakeResponse(body: utf8.encode('void main() { String? foo; print(foo); } // ignore: avoid_print')),
           )
         ]);
       };
@@ -2450,6 +2457,47 @@ void main() {
     FeatureFlags: () => TestFeatureFlags(isWindowsEnabled: true, isAndroidEnabled: false, isIOSEnabled: false),
     Logger: () => logger,
   });
+
+  testUsingContext('default project has analysis_options.yaml set up correctly', () async {
+    await _createProject(
+        projectDir,
+        <String>[],
+        <String>[
+          'analysis_options.yaml',
+        ],
+    );
+    final String dataPath = globals.fs.path.join(
+      getFlutterRoot(),
+      'packages',
+      'flutter_tools',
+      'test',
+      'commands.shard',
+      'permeable',
+      'data',
+    );
+    final File toAnalyze = await globals.fs.file(globals.fs.path.join(dataPath, 'to_analyze.dart.test'))
+        .copy(globals.fs.path.join(projectDir.path, 'lib', 'to_analyze.dart'));
+    final String relativePath = globals.fs.path.join('lib', 'to_analyze.dart');
+    final List<String> expectedFailures = <String>[
+      '$relativePath:11:7: use_key_in_widget_constructors',
+      '$relativePath:20:3: prefer_const_constructors_in_immutables',
+      '$relativePath:31:26: use_full_hex_values_for_flutter_colors',
+    ];
+    expect(expectedFailures.length, '// LINT:'.allMatches(toAnalyze.readAsStringSync()).length);
+    await _analyzeProject(
+      projectDir.path,
+      expectedFailures: expectedFailures,
+    );
+  }, overrides: <Type, Generator>{
+    Pub: () => Pub(
+      fileSystem: globals.fs,
+      logger: globals.logger,
+      processManager: globals.processManager,
+      usage: globals.flutterUsage,
+      botDetector: globals.botDetector,
+      platform: globals.platform,
+    ),
+  });
 }
 
 Future<void> _createProject(
@@ -2548,7 +2596,7 @@ Future<void> _restoreFlutterToolsSnapshot() async {
   snapshotBackup.renameSync(flutterToolsSnapshotPath);
 }
 
-Future<void> _analyzeProject(String workingDir) async {
+Future<void> _analyzeProject(String workingDir, { List<String> expectedFailures = const <String>[] }) async {
   final String flutterToolsSnapshotPath = globals.fs.path.absolute(globals.fs.path.join(
     '..',
     '..',
@@ -2567,11 +2615,27 @@ Future<void> _analyzeProject(String workingDir) async {
     args,
     workingDirectory: workingDir,
   );
+  if (expectedFailures.isEmpty) {
     if (exec.exitCode != 0) {
       print(exec.stdout);
       print(exec.stderr);
     }
     expect(exec.exitCode, 0);
+    return;
+  }
+  expect(exec.exitCode, isNot(0));
+  String lineParser(String line) {
+    print('#$line#');
+    final String analyzerSeparator = globals.platform.isWindows ? ' - ' : ' • ';
+    final List<String> lineComponents = line.trim().split(analyzerSeparator);
+    final String lintName = lineComponents.removeLast();
+    final String location = lineComponents.removeLast();
+    return '$location: $lintName';
+  }
+  final List<String> errors = const LineSplitter().convert(exec.stdout.toString())
+      .where((String line) => line.trim().isNotEmpty && !line.startsWith('Analyzing'))
+      .map(lineParser).toList();
+  expect(errors, unorderedEquals(expectedFailures));
 }
 
 Future<void> _runFlutterTest(Directory workingDir, { String target }) async {

packages/flutter_tools/test/commands.shard/permeable/data/to_analyze.dart.test

+// 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:flutter/widgets.dart';
+
+// Test file used by `create_test.dart` to verify that `flutter create` sets up
+// `analysis_options.yaml` correctly to activate certain lints and ensures
+// that lints not playing well with Flutter remain disabled.
+
+class NoConstructor extends StatelessWidget {
+  // LINT: Missing constructor generates use_key_in_widget_constructors warning.
+
+  @override
+  Widget build(BuildContext context) => Container();
+}
+
+class NoConstConstructor extends StatelessWidget {
+  // LINT: Missing const constructor generates prefer_const_constructors_in_immutables warning.
+  NoConstConstructor({Key? key, required this.name }) : super(key: key);
+
+  final String name;
+
+  @override
+  Widget build(BuildContext context) {
+    // NO LINT: Can type local variables without omit_local_variable_types warning.
+    final String text = 'Hello $name';
+
+    return Container(
+      // LINT: "Color(0x1)" generates use_full_hex_values_for_flutter_colors warning.
+      color: const Color(0x1),
+      child: Text(text),
+    );
+  }
+}
+
+Future<void> playAsync(AnimationController controller) async {
+  // NO LINT: AnimationController API can be called without await and without
+  // marking Future as unawaited, https://github.com/dart-lang/linter/issues/2513.
+  controller.forward();
+}
+
+Future<void> pushAsync(NavigatorState navigator) async {
+  // NO LINT: Navigator API can be called without await and without
+  // marking Future as unawaited, https://github.com/dart-lang/linter/issues/2513.
+  navigator.pushNamed('foo');
+}
+
+// NO LINT: Can extend ChangeNotifier without warning, https://github.com/dart-lang/sdk/issues/45343.
+class ExtendingChangeNotifier extends ChangeNotifier { }
+
+// NO LINT: Can mixin ChangeNotifier without warning, https://github.com/dart-lang/sdk/issues/45343.
+class MixingChangeNotifier with ChangeNotifier { }
+
+// NO LINT: Can extend WidgetsBindingObserver without warning, https://github.com/dart-lang/sdk/issues/45343.
+class ExtendingWidgetsBindingObserver extends WidgetsBindingObserver { }
+
+// NO LINT: Can mixin WidgetsBindingObserver without warning, https://github.com/dart-lang/sdk/issues/45343.
+class MixingWidgetsBindingObserver with WidgetsBindingObserver { }