Add flutter_lints to form_app (#822)

form_app/lib/src/autofill.dart

@@ -7,6 +7,8 @@ import 'package:flutter/material.dart';
 // Demonstrates how to use autofill hints. The full list of hints is here:
 // https://github.com/flutter/engine/blob/master/lib/web_ui/lib/src/engine/text_editing/autofill_hint.dart
 class AutofillDemo extends StatefulWidget {
+  const AutofillDemo({Key key}) : super(key: key);
+
   @override
   _AutofillDemoState createState() => _AutofillDemoState();
 }
@@ -18,36 +20,36 @@ class _AutofillDemoState extends State<AutofillDemo> {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: Text('Autofill'),
+        title: const Text('Autofill'),
       ),
       body: Form(
         key: _formKey,
         child: Scrollbar(
           child: SingleChildScrollView(
-            padding: EdgeInsets.all(16),
+            padding: const EdgeInsets.all(16),
             child: AutofillGroup(
               child: Column(
                 children: [
                   ...[
-                    Text('This sample demonstrates autofill. '),
+                    const Text('This sample demonstrates autofill. '),
                     TextFormField(
                       autofocus: true,
                       textInputAction: TextInputAction.next,
-                      decoration: InputDecoration(
+                      decoration: const InputDecoration(
                         hintText: 'Jane',
                         labelText: 'First Name',
                       ),
-                      autofillHints: [AutofillHints.givenName],
+                      autofillHints: const [AutofillHints.givenName],
                     ),
                     TextFormField(
                       textInputAction: TextInputAction.next,
-                      decoration: InputDecoration(
+                      decoration: const InputDecoration(
                         hintText: 'Doe',
                         labelText: 'Last Name',
                       ),
-                      autofillHints: [AutofillHints.familyName],
+                      autofillHints: const [AutofillHints.familyName],
                     ),
-                    TextField(
+                    const TextField(
                       keyboardType: TextInputType.emailAddress,
                       textInputAction: TextInputAction.next,
                       decoration: InputDecoration(
@@ -56,7 +58,7 @@ class _AutofillDemoState extends State<AutofillDemo> {
                       ),
                       autofillHints: [AutofillHints.email],
                     ),
-                    TextField(
+                    const TextField(
                       keyboardType: TextInputType.phone,
                       textInputAction: TextInputAction.next,
                       decoration: InputDecoration(
@@ -65,7 +67,7 @@ class _AutofillDemoState extends State<AutofillDemo> {
                       ),
                       autofillHints: <String>[AutofillHints.telephoneNumber],
                     ),
-                    TextField(
+                    const TextField(
                       keyboardType: TextInputType.streetAddress,
                       textInputAction: TextInputAction.next,
                       decoration: InputDecoration(
@@ -74,7 +76,7 @@ class _AutofillDemoState extends State<AutofillDemo> {
                       ),
                       autofillHints: <String>[AutofillHints.streetAddressLine1],
                     ),
-                    TextField(
+                    const TextField(
                       keyboardType: TextInputType.number,
                       textInputAction: TextInputAction.next,
                       decoration: InputDecoration(
@@ -83,7 +85,7 @@ class _AutofillDemoState extends State<AutofillDemo> {
                       ),
                       autofillHints: <String>[AutofillHints.postalCode],
                     ),
-                    TextField(
+                    const TextField(
                       textInputAction: TextInputAction.next,
                       decoration: InputDecoration(
                         hintText: 'United States',
@@ -91,7 +93,7 @@ class _AutofillDemoState extends State<AutofillDemo> {
                       ),
                       autofillHints: <String>[AutofillHints.countryName],
                     ),
-                    TextField(
+                    const TextField(
                       keyboardType: TextInputType.number,
                       decoration: InputDecoration(
                         hintText: '1',
@@ -102,7 +104,7 @@ class _AutofillDemoState extends State<AutofillDemo> {
                   ].expand(
                     (widget) => [
                       widget,
-                      SizedBox(
+                      const SizedBox(
                         height: 24,
                       )
                     ],

form_app/lib/src/form_widgets.dart

@@ -6,6 +6,8 @@ import 'package:flutter/material.dart';
 import 'package:intl/intl.dart' as intl;
 
 class FormWidgetsDemo extends StatefulWidget {
+  const FormWidgetsDemo({Key key}) : super(key: key);
+
   @override
   _FormWidgetsDemoState createState() => _FormWidgetsDemoState();
 }
@@ -23,7 +25,7 @@ class _FormWidgetsDemoState extends State<FormWidgetsDemo> {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: Text('Form widgets'),
+        title: const Text('Form widgets'),
       ),
       body: Form(
         key: _formKey,
@@ -32,16 +34,16 @@ class _FormWidgetsDemoState extends State<FormWidgetsDemo> {
             alignment: Alignment.topCenter,
             child: Card(
               child: SingleChildScrollView(
-                padding: EdgeInsets.all(16),
+                padding: const EdgeInsets.all(16),
                 child: ConstrainedBox(
-                  constraints: BoxConstraints(maxWidth: 400),
+                  constraints: const BoxConstraints(maxWidth: 400),
                   child: Column(
                     mainAxisAlignment: MainAxisAlignment.center,
                     crossAxisAlignment: CrossAxisAlignment.center,
                     children: [
                       ...[
                         TextFormField(
-                          decoration: InputDecoration(
+                          decoration: const InputDecoration(
                             filled: true,
                             hintText: 'Enter a title...',
                             labelText: 'Title',
@@ -53,8 +55,8 @@ class _FormWidgetsDemoState extends State<FormWidgetsDemo> {
                           },
                         ),
                         TextFormField(
-                          decoration: InputDecoration(
-                            border: const OutlineInputBorder(),
+                          decoration: const InputDecoration(
+                            border: OutlineInputBorder(),
                             filled: true,
                             hintText: 'Enter a description...',
                             labelText: 'Description',
@@ -64,7 +66,7 @@ class _FormWidgetsDemoState extends State<FormWidgetsDemo> {
                           },
                           maxLines: 5,
                         ),
-                        _FormDatePicker(
+                        _FormDatePicker<DateTime>(
                           date: date,
                           onChanged: (value) {
                             setState(() {
@@ -139,7 +141,7 @@ class _FormWidgetsDemoState extends State<FormWidgetsDemo> {
                       ].expand(
                         (widget) => [
                           widget,
-                          SizedBox(
+                          const SizedBox(
                             height: 24,
                           )
                         ],
@@ -156,11 +158,11 @@ class _FormWidgetsDemoState extends State<FormWidgetsDemo> {
   }
 }
 
-class _FormDatePicker extends StatefulWidget {
+class _FormDatePicker<T> extends StatefulWidget {
   final DateTime date;
-  final ValueChanged onChanged;
+  final ValueChanged<T> onChanged;
 
-  _FormDatePicker({
+  const _FormDatePicker({
     this.date,
     this.onChanged,
   });
@@ -191,7 +193,7 @@ class _FormDatePickerState extends State<_FormDatePicker> {
           ],
         ),
         TextButton(
-          child: Text('Edit'),
+          child: const Text('Edit'),
           onPressed: () async {
             var newDate = await showDatePicker(
               context: context,

form_app/lib/src/http/mock_client.dart

@@ -11,10 +11,10 @@ class MockClient extends Mock implements http.Client {
   MockClient() {
     when(post('https://example.com/signin', body: anyNamed('body')))
         .thenAnswer((answering) {
-      var body = answering.namedArguments[Symbol('body')];
+      dynamic body = answering.namedArguments[const Symbol('body')];
 
       if (body != null && body is String) {
-        var decodedJson = json.decode(body);
+        var decodedJson = json.decode(body) as Map<String, String>;
 
         if (decodedJson['email'] == 'root' &&
             decodedJson['password'] == 'password') {

form_app/lib/src/sign_in_http.dart

@@ -29,9 +29,10 @@ class FormData {
 class SignInHttpDemo extends StatefulWidget {
   final http.Client httpClient;
 
-  SignInHttpDemo({
+  const SignInHttpDemo({
     this.httpClient,
-  });
+    Key key,
+  }) : super(key: key);
 
   @override
   _SignInHttpDemoState createState() => _SignInHttpDemoState();
@@ -44,19 +45,19 @@ class _SignInHttpDemoState extends State<SignInHttpDemo> {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: Text('Sign in Form'),
+        title: const Text('Sign in Form'),
       ),
       body: Form(
         child: Scrollbar(
           child: SingleChildScrollView(
-            padding: EdgeInsets.all(16),
+            padding: const EdgeInsets.all(16),
             child: Column(
               children: [
                 ...[
                   TextFormField(
-                    autofocus:  true,
+                    autofocus: true,
                     textInputAction: TextInputAction.next,
-                    decoration: InputDecoration(
+                    decoration: const InputDecoration(
                       filled: true,
                       hintText: 'Your email address',
                       labelText: 'Email',
@@ -66,7 +67,7 @@ class _SignInHttpDemoState extends State<SignInHttpDemo> {
                     },
                   ),
                   TextFormField(
-                    decoration: InputDecoration(
+                    decoration: const InputDecoration(
                       filled: true,
                       labelText: 'Password',
                     ),
@@ -76,7 +77,7 @@ class _SignInHttpDemoState extends State<SignInHttpDemo> {
                     },
                   ),
                   TextButton(
-                    child: Text('Sign in'),
+                    child: const Text('Sign in'),
                     onPressed: () async {
                       // Use a JSON encoded string to send
                       var result = await widget.httpClient.post(
@@ -96,7 +97,7 @@ class _SignInHttpDemoState extends State<SignInHttpDemo> {
                 ].expand(
                   (widget) => [
                     widget,
-                    SizedBox(
+                    const SizedBox(
                       height: 24,
                     )
                   ],
@@ -110,13 +111,13 @@ class _SignInHttpDemoState extends State<SignInHttpDemo> {
   }
 
   void _showDialog(String message) {
-    showDialog(
+    showDialog<void>(
       context: context,
       builder: (context) => AlertDialog(
         title: Text(message),
         actions: [
           TextButton(
-            child: Text('OK'),
+            child: const Text('OK'),
             onPressed: () => Navigator.of(context).pop(),
           ),
         ],

form_app/lib/src/validation.dart

@@ -6,6 +6,8 @@ import 'package:flutter/material.dart';
 import 'package:english_words/english_words.dart' as english_words;
 
 class FormValidationDemo extends StatefulWidget {
+  const FormValidationDemo({Key key}) : super(key: key);
+
   @override
   _FormValidationDemoState createState() => _FormValidationDemoState();
 }
@@ -20,13 +22,13 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: Text('📖 Story Generator'),
+        title: const Text('📖 Story Generator'),
         actions: [
           Padding(
-            padding: EdgeInsets.all(8),
+            padding: const EdgeInsets.all(8),
             child: TextButton(
               style: TextButton.styleFrom(primary: Colors.white),
-              child: Text('Submit'),
+              child: const Text('Submit'),
               onPressed: () {
                 // Validate the form by getting the FormState from the GlobalKey
                 // and calling validate() on it.
@@ -35,14 +37,14 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
                   return;
                 }
 
-                showDialog(
+                showDialog<void>(
                   context: context,
                   builder: (context) => AlertDialog(
-                    title: Text('Your story'),
+                    title: const Text('Your story'),
                     content: Text('The $adjective developer saw a $noun'),
                     actions: [
                       TextButton(
-                        child: Text('Done'),
+                        child: const Text('Done'),
                         onPressed: () {
                           Navigator.of(context).pop();
                         },
@@ -59,7 +61,7 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
         key: _formKey,
         child: Scrollbar(
           child: SingleChildScrollView(
-            padding: EdgeInsets.all(16),
+            padding: const EdgeInsets.all(16),
             child: Column(
               children: [
                 // A text field that validates that the text is an adjective.
@@ -75,7 +77,7 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
                     }
                     return 'Not a valid adjective.';
                   },
-                  decoration: InputDecoration(
+                  decoration: const InputDecoration(
                     filled: true,
                     hintText: 'e.g. quick, beautiful, interesting',
                     labelText: 'Enter an adjective',
@@ -84,7 +86,7 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
                     adjective = value;
                   },
                 ),
-                SizedBox(
+                const SizedBox(
                   height: 24,
                 ),
                 // A text field that validates that the text is a noun.
@@ -98,7 +100,7 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
                     }
                     return 'Not a valid noun.';
                   },
-                  decoration: InputDecoration(
+                  decoration: const InputDecoration(
                     filled: true,
                     hintText: 'i.e. a person, place or thing',
                     labelText: 'Enter a noun',
@@ -107,12 +109,12 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
                     noun = value;
                   },
                 ),
-                SizedBox(
+                const SizedBox(
                   height: 24,
                 ),
                 // A custom form field that requires the user to check a
                 // checkbox.
-                FormField(
+                FormField<bool>(
                   initialValue: false,
                   validator: (value) {
                     if (value == false) {
@@ -120,7 +122,7 @@ class _FormValidationDemoState extends State<FormValidationDemo> {
                     }
                     return null;
                   },
-                  builder: (FormFieldState formFieldState) {
+                  builder: (formFieldState) {
                     return Column(
                       crossAxisAlignment: CrossAxisAlignment.start,
                       children: [