Add flutter_lints to null_safety (#828)

null_safety/null_safe_app/analysis_options.yaml

@@ -0,0 +1,19 @@
+include: package:flutter_lints/flutter.yaml
+
+analyzer:
+  strong-mode:
+    implicit-casts: false
+    implicit-dynamic: false
+
+linter:
+  rules:
+    avoid_types_on_closure_parameters: true
+    avoid_void_async: true
+    cancel_subscriptions: true
+    close_sinks: true
+    directives_ordering: true
+    package_api_docs: true
+    package_prefixed_library_names: true
+    test_types_in_equals: true
+    throw_in_finally: true
+    unnecessary_statements: true

null_safety/null_safe_app/lib/badapp.dart

@@ -12,13 +12,15 @@ import 'services.dart';
 // uncomment the for-loop and appBar lines below, and note how the new null
 // safety static analysis immediately flags those lines as errors.
 class BadMyApp extends StatelessWidget {
+  const BadMyApp({Key? key}) : super(key: key);
+
   @override
   Widget build(BuildContext context) {
     final localizedAppName = Config.getAppName();
     final temperatures = WeatherService.getTemperatures();
 
     var tempWidgets = [
-      Text('Temperature next 3 days:'),
+      const Text('Temperature next 3 days:'),
       // for (final t in temperatures) Text(t.round().toString()),
     ];
 

null_safety/null_safe_app/lib/goodapp.dart

@@ -7,6 +7,8 @@ import 'package:flutter/material.dart';
 import 'services.dart';
 
 class GoodMyApp extends StatelessWidget {
+  const GoodMyApp({Key? key}) : super(key: key);
+
   @override
   Widget build(BuildContext context) {
     final localizedAppName = Config.getAppName();
@@ -14,13 +16,13 @@ class GoodMyApp extends StatelessWidget {
 
     List<Widget> tempWidgets;
     if (temperatures == null) {
-      tempWidgets = [Text('Temperature: Failed getting forecast :-(')];
+      tempWidgets = [const Text('Temperature: Failed getting forecast :-(')];
     } else {
       // Null safety uses flow analysis. The code checked for null in the branch
       // above, so in this branch it known that temperatures cannot be null.
       // Notice how we access temperatures without getting an analysis error.
       tempWidgets = [
-        Text('Temperature next 3 days:'),
+        const Text('Temperature next 3 days:'),
         for (final t in temperatures)
           // We first use the conditional member access operator to only call
           // round() and toString() if t isn't null. We then test if that

null_safety/null_safe_app/lib/main.dart

@@ -7,5 +7,5 @@ import 'package:flutter/material.dart';
 import 'goodapp.dart';
 
 void main() {
-  runApp(GoodMyApp());
+  runApp(const GoodMyApp());
 }

null_safety/null_safe_app/pubspec.lock

@@ -62,11 +62,25 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_lints:
+    dependency: "direct dev"
+    description:
+      name: flutter_lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.3"
   flutter_test:
     dependency: "direct dev"
     description: flutter
     source: sdk
     version: "0.0.0"
+  lints:
+    dependency: transitive
+    description:
+      name: lints
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "1.0.1"
   matcher:
     dependency: transitive
     description:

null_safety/null_safe_app/pubspec.yaml

@@ -1,6 +1,6 @@
 name: null_safe_app
 description: A new Flutter project.
-publish_to: 'none' # Do not publish apps & package using the null safety experiment.
+publish_to: "none" # Do not publish apps & package using the null safety experiment.
 version: 1.2.0
 
 environment:
@@ -15,6 +15,7 @@ dependencies:
 dev_dependencies:
   flutter_test:
     sdk: flutter
+  flutter_lints: ^1.0.0
 
 flutter:
   uses-material-design: true

null_safety/null_safe_app/test/widget_test.dart

@@ -4,9 +4,9 @@ import 'package:flutter_test/flutter_test.dart';
 import 'package:null_safe_app/goodapp.dart';
 
 void main() {
-  testWidgets('App smoke test', (WidgetTester tester) async {
+  testWidgets('App smoke test', (tester) async {
     // Build our app and trigger a frame.
-    await tester.pumpWidget(GoodMyApp());
+    await tester.pumpWidget(const GoodMyApp());
 
     // Verify that we have a forecast, or a managed failure.
     expect(find.textContaining('Temperature'), findsOneWidget);