FormField should autovalidate only if its content was changed (fixed) (#59766)

packages/flutter/lib/src/material/dropdown.dart

@@ -1437,7 +1437,7 @@ class DropdownButtonFormField<T> extends FormField<T> {
   /// Creates a [DropdownButton] widget that is a [FormField], wrapped in an
   /// [InputDecorator].
   ///
-  /// For a description of the `onSaved`, `validator`, or `autovalidate`
+  /// For a description of the `onSaved`, `validator`, or `autovalidateMode`
   /// parameters, see [FormField]. For the rest (other than [decoration]), see
   /// [DropdownButton].
   ///
@@ -1469,6 +1469,7 @@ class DropdownButtonFormField<T> extends FormField<T> {
     FormFieldSetter<T> onSaved,
     FormFieldValidator<T> validator,
     bool autovalidate = false,
+    AutovalidateMode autovalidateMode,
   }) : assert(items == null || items.isEmpty || value == null ||
               items.where((DropdownMenuItem<T> item) {
                 return item.value == value;
@@ -1484,13 +1485,21 @@ class DropdownButtonFormField<T> extends FormField<T> {
        assert(isExpanded != null),
        assert(itemHeight == null || itemHeight >= kMinInteractiveDimension),
        assert(autofocus != null),
+       assert(autovalidate != null),
+       assert(
+         autovalidate == false ||
+         autovalidate == true && autovalidateMode == null,
+         'autovalidate and autovalidateMode should not be used together.'
+       ),
        decoration = decoration ?? InputDecoration(focusColor: focusColor),
        super(
          key: key,
          onSaved: onSaved,
          initialValue: value,
          validator: validator,
-         autovalidate: autovalidate,
+         autovalidateMode: autovalidate
+             ? AutovalidateMode.always
+             : (autovalidateMode ?? AutovalidateMode.disabled),
          builder: (FormFieldState<T> field) {
            final _DropdownButtonFormFieldState<T> state = field as _DropdownButtonFormFieldState<T>;
            final InputDecoration decorationArg =  decoration ?? InputDecoration(focusColor: focusColor);

packages/flutter/lib/src/material/text_form_field.dart

@@ -180,6 +180,7 @@ class TextFormField extends FormField<String> {
     InputCounterWidgetBuilder buildCounter,
     ScrollPhysics scrollPhysics,
     Iterable<String> autofillHints,
+    AutovalidateMode autovalidateMode,
   }) : assert(initialValue == null || controller == null),
        assert(textAlign != null),
        assert(autofocus != null),
@@ -189,6 +190,11 @@ class TextFormField extends FormField<String> {
        assert(autocorrect != null),
        assert(enableSuggestions != null),
        assert(autovalidate != null),
+       assert(
+         autovalidate == false ||
+         autovalidate == true && autovalidateMode == null,
+         'autovalidate and autovalidateMode should not be used together.'
+       ),
        assert(maxLengthEnforced != null),
        assert(scrollPadding != null),
        assert(maxLines == null || maxLines > 0),
@@ -206,67 +212,69 @@ class TextFormField extends FormField<String> {
        assert(maxLength == null || maxLength > 0),
        assert(enableInteractiveSelection != null),
        super(
-    key: key,
-    initialValue: controller != null ? controller.text : (initialValue ?? ''),
-    onSaved: onSaved,
-    validator: validator,
-    autovalidate: autovalidate,
-    enabled: enabled ?? decoration?.enabled ?? true,
-    builder: (FormFieldState<String> field) {
-      final _TextFormFieldState state = field as _TextFormFieldState;
-      final InputDecoration effectiveDecoration = (decoration ?? const InputDecoration())
-        .applyDefaults(Theme.of(field.context).inputDecorationTheme);
-      void onChangedHandler(String value) {
-        if (onChanged != null) {
-          onChanged(value);
-        }
-        field.didChange(value);
-      }
-      return TextField(
-        controller: state._effectiveController,
-        focusNode: focusNode,
-        decoration: effectiveDecoration.copyWith(errorText: field.errorText),
-        keyboardType: keyboardType,
-        textInputAction: textInputAction,
-        style: style,
-        strutStyle: strutStyle,
-        textAlign: textAlign,
-        textAlignVertical: textAlignVertical,
-        textDirection: textDirection,
-        textCapitalization: textCapitalization,
-        autofocus: autofocus,
-        toolbarOptions: toolbarOptions,
-        readOnly: readOnly,
-        showCursor: showCursor,
-        obscuringCharacter: obscuringCharacter,
-        obscureText: obscureText,
-        autocorrect: autocorrect,
-        smartDashesType: smartDashesType ?? (obscureText ? SmartDashesType.disabled : SmartDashesType.enabled),
-        smartQuotesType: smartQuotesType ?? (obscureText ? SmartQuotesType.disabled : SmartQuotesType.enabled),
-        enableSuggestions: enableSuggestions,
-        maxLengthEnforced: maxLengthEnforced,
-        maxLines: maxLines,
-        minLines: minLines,
-        expands: expands,
-        maxLength: maxLength,
-        onChanged: onChangedHandler,
-        onTap: onTap,
-        onEditingComplete: onEditingComplete,
-        onSubmitted: onFieldSubmitted,
-        inputFormatters: inputFormatters,
-        enabled: enabled ?? decoration?.enabled ?? true,
-        cursorWidth: cursorWidth,
-        cursorRadius: cursorRadius,
-        cursorColor: cursorColor,
-        scrollPadding: scrollPadding,
-        scrollPhysics: scrollPhysics,
-        keyboardAppearance: keyboardAppearance,
-        enableInteractiveSelection: enableInteractiveSelection,
-        buildCounter: buildCounter,
-        autofillHints: autofillHints,
-      );
-    },
-  );
+       key: key,
+       initialValue: controller != null ? controller.text : (initialValue ?? ''),
+       onSaved: onSaved,
+       validator: validator,
+       enabled: enabled ?? decoration?.enabled ?? true,
+       autovalidateMode: autovalidate
+           ? AutovalidateMode.always
+           : (autovalidateMode ?? AutovalidateMode.disabled),
+       builder: (FormFieldState<String> field) {
+         final _TextFormFieldState state = field as _TextFormFieldState;
+         final InputDecoration effectiveDecoration = (decoration ?? const InputDecoration())
+             .applyDefaults(Theme.of(field.context).inputDecorationTheme);
+         void onChangedHandler(String value) {
+           if (onChanged != null) {
+             onChanged(value);
+           }
+           field.didChange(value);
+         }
+         return TextField(
+           controller: state._effectiveController,
+           focusNode: focusNode,
+           decoration: effectiveDecoration.copyWith(errorText: field.errorText),
+           keyboardType: keyboardType,
+           textInputAction: textInputAction,
+           style: style,
+           strutStyle: strutStyle,
+           textAlign: textAlign,
+           textAlignVertical: textAlignVertical,
+           textDirection: textDirection,
+           textCapitalization: textCapitalization,
+           autofocus: autofocus,
+           toolbarOptions: toolbarOptions,
+           readOnly: readOnly,
+           showCursor: showCursor,
+           obscuringCharacter: obscuringCharacter,
+           obscureText: obscureText,
+           autocorrect: autocorrect,
+           smartDashesType: smartDashesType ?? (obscureText ? SmartDashesType.disabled : SmartDashesType.enabled),
+           smartQuotesType: smartQuotesType ?? (obscureText ? SmartQuotesType.disabled : SmartQuotesType.enabled),
+           enableSuggestions: enableSuggestions,
+           maxLengthEnforced: maxLengthEnforced,
+           maxLines: maxLines,
+           minLines: minLines,
+           expands: expands,
+           maxLength: maxLength,
+           onChanged: onChangedHandler,
+           onTap: onTap,
+           onEditingComplete: onEditingComplete,
+           onSubmitted: onFieldSubmitted,
+           inputFormatters: inputFormatters,
+           enabled: enabled ?? decoration?.enabled ?? true,
+           cursorWidth: cursorWidth,
+           cursorRadius: cursorRadius,
+           cursorColor: cursorColor,
+           scrollPadding: scrollPadding,
+           scrollPhysics: scrollPhysics,
+           keyboardAppearance: keyboardAppearance,
+           enableInteractiveSelection: enableInteractiveSelection,
+           buildCounter: buildCounter,
+           autofillHints: autofillHints,
+         );
+       },
+     );
 
   /// Controls the text being edited.
   ///

packages/flutter/lib/src/widgets/form.dart

@@ -81,7 +81,17 @@ class Form extends StatefulWidget {
     this.autovalidate = false,
     this.onWillPop,
     this.onChanged,
+    AutovalidateMode autovalidateMode,
   }) : assert(child != null),
+       assert(autovalidate != null),
+       assert(
+         autovalidate == false ||
+         autovalidate == true && autovalidateMode == null,
+         'autovalidate and autovalidateMode should not be used together.'
+       ),
+       autovalidateMode = autovalidate
+           ? AutovalidateMode.always
+           : (autovalidateMode ?? AutovalidateMode.disabled),
        super(key: key);
 
   /// Returns the closest [FormState] which encloses the given context.
@@ -127,6 +137,12 @@ class Form extends StatefulWidget {
   /// will rebuild.
   final VoidCallback onChanged;
 
+  /// Used to enable/disable form fields auto validation and update their error
+  /// text.
+  ///
+  /// {@macro flutter.widgets.form.autovalidateMode}
+  final AutovalidateMode autovalidateMode;
+
   @override
   FormState createState() => FormState();
 }
@@ -139,6 +155,7 @@ class Form extends StatefulWidget {
 /// Typically obtained via [Form.of].
 class FormState extends State<Form> {
   int _generation = 0;
+  bool _hasInteractedByUser = false;
   final Set<FormFieldState<dynamic>> _fields = <FormFieldState<dynamic>>{};
 
   // Called when a form field has changed. This will cause all form fields
@@ -146,6 +163,10 @@ class FormState extends State<Form> {
   void _fieldDidChange() {
     if (widget.onChanged != null)
       widget.onChanged();
+
+
+    _hasInteractedByUser = _fields
+        .any((FormFieldState<dynamic> field) => field._hasInteractedByUser);
     _forceRebuild();
   }
 
@@ -165,8 +186,19 @@ class FormState extends State<Form> {
 
   @override
   Widget build(BuildContext context) {
-    if (widget.autovalidate)
-      _validate();
+    switch (widget.autovalidateMode) {
+      case AutovalidateMode.always:
+        _validate();
+        break;
+      case AutovalidateMode.onUserInteraction:
+        if (_hasInteractedByUser) {
+          _validate();
+        }
+        break;
+      case AutovalidateMode.disabled:
+        break;
+    }
+
     return WillPopScope(
       onWillPop: widget.onWillPop,
       child: _FormScope(
@@ -188,11 +220,12 @@ class FormState extends State<Form> {
   ///
   /// The [Form.onChanged] callback will be called.
   ///
-  /// If the form's [Form.autovalidate] property is true, the fields will all be
-  /// revalidated after being reset.
+  /// If the form's [Form.autovalidateMode] property is [AutovalidateMode.always],
+  /// the fields will all be revalidated after being reset.
   void reset() {
     for (final FormFieldState<dynamic> field in _fields)
       field.reset();
+    _hasInteractedByUser = false;
     _fieldDidChange();
   }
 
@@ -201,6 +234,7 @@ class FormState extends State<Form> {
   ///
   /// The form will rebuild to report the results.
   bool validate() {
+    _hasInteractedByUser = true;
     _forceRebuild();
     return _validate();
   }
@@ -287,7 +321,16 @@ class FormField<T> extends StatefulWidget {
     this.initialValue,
     this.autovalidate = false,
     this.enabled = true,
+    AutovalidateMode autovalidateMode,
   }) : assert(builder != null),
+       assert(
+         autovalidate == false ||
+         autovalidate == true && autovalidateMode == null,
+         'autovalidate and autovalidateMode should not be used together.'
+       ),
+       autovalidateMode = autovalidate
+           ? AutovalidateMode.always
+           : (autovalidateMode ?? AutovalidateMode.disabled),
        super(key: key);
 
   /// An optional method to call with the final value when the form is saved via
@@ -325,11 +368,26 @@ class FormField<T> extends StatefulWidget {
 
   /// Whether the form is able to receive user input.
   ///
-  /// Defaults to true. If [autovalidate] is true, the field will be validated.
-  /// Likewise, if this field is false, the widget will not be validated
-  /// regardless of [autovalidate].
+  /// Defaults to true. If [autovalidateMode] is not [AutovalidateMode.disabled],
+  /// the field will be auto validated. Likewise, if this field is false, the widget
+  /// will not be validated regardless of [autovalidateMode].
   final bool enabled;
 
+  /// Used to enable/disable this form field auto validation and update its
+  /// error text.
+  ///
+  /// {@template flutter.widgets.form.autovalidateMode}
+  /// If [AutovalidateMode.onUserInteraction] this form field will only
+  /// auto-validate after its content changes, if [AutovalidateMode.always] it
+  /// will auto validate even without user interaction and
+  /// if [AutovalidateMode.disabled] the auto validation will be disabled.
+  ///
+  /// Defaults to [AutovalidateMode.disabled] if [autovalidate] is false which
+  /// means no auto validation will occur. If [autovalidate] is true then this
+  /// is set to [AutovalidateMode.always] for backward compatibility.
+  /// {@endtemplate}
+  final AutovalidateMode autovalidateMode;
+
   @override
   FormFieldState<T> createState() => FormFieldState<T>();
 }
@@ -339,6 +397,7 @@ class FormField<T> extends StatefulWidget {
 class FormFieldState<T> extends State<FormField<T>> {
   T _value;
   String _errorText;
+  bool _hasInteractedByUser = false;
 
   /// The current value of the form field.
   T get value => _value;
@@ -371,8 +430,10 @@ class FormFieldState<T> extends State<FormField<T>> {
   void reset() {
     setState(() {
       _value = widget.initialValue;
+      _hasInteractedByUser = false;
       _errorText = null;
     });
+    Form.of(context)?._fieldDidChange();
   }
 
   /// Calls [FormField.validator] to set the [errorText]. Returns true if there
@@ -397,11 +458,13 @@ class FormFieldState<T> extends State<FormField<T>> {
   /// Updates this field's state to the new value. Useful for responding to
   /// child widget changes, e.g. [Slider]'s [Slider.onChanged] argument.
   ///
-  /// Triggers the [Form.onChanged] callback and, if the [Form.autovalidate]
-  /// field is set, revalidates all the fields of the form.
+  /// Triggers the [Form.onChanged] callback and, if [Form.autovalidateMode] is
+  /// [AutovalidateMode.always] or [AutovalidateMode.onUserInteraction],
+  /// revalidates all the fields of the form.
   void didChange(T value) {
     setState(() {
       _value = value;
+      _hasInteractedByUser = true;
     });
     Form.of(context)?._fieldDidChange();
   }
@@ -432,10 +495,34 @@ class FormFieldState<T> extends State<FormField<T>> {
 
   @override
   Widget build(BuildContext context) {
-    // Only autovalidate if the widget is also enabled
-    if (widget.autovalidate && widget.enabled)
-      _validate();
+    if (widget.enabled) {
+      switch (widget.autovalidateMode) {
+        case AutovalidateMode.always:
+          _validate();
+          break;
+        case AutovalidateMode.onUserInteraction:
+          if (_hasInteractedByUser) {
+            _validate();
+          }
+          break;
+        case AutovalidateMode.disabled:
+          break;
+      }
+    }
     Form.of(context)?._register(this);
     return widget.builder(this);
   }
 }
+
+/// Used to configure the auto validation of [FormField] and [Form] widgets.
+enum AutovalidateMode {
+  /// No auto validation will occur.
+  disabled,
+
+  /// Used to auto-validate [Form] and [FormField] even without user interaction.
+  always,
+
+  /// Used to auto-validate [Form] and [FormField] only after each user
+  /// interaction.
+  onUserInteraction,
+}

packages/flutter/test/material/dropdown_form_field_test.dart

@@ -29,7 +29,7 @@ Finder _iconRichText(Key iconKey) {
 
 Widget buildFormFrame({
   Key buttonKey,
-  bool autovalidate = false,
+  AutovalidateMode autovalidateMode = AutovalidateMode.disabled,
   int elevation = 8,
   String value = 'two',
   ValueChanged<String> onChanged,
@@ -55,7 +55,7 @@ Widget buildFormFrame({
         child: RepaintBoundary(
           child: DropdownButtonFormField<String>(
             key: buttonKey,
-            autovalidate: autovalidate,
+            autovalidateMode: autovalidateMode,
             elevation: elevation,
             value: value,
             hint: hint,
@@ -180,7 +180,7 @@ void main() {
                   _validateCalled++;
                   return currentValue == null ? 'Must select value' : null;
                 },
-                autovalidate: true,
+                autovalidateMode: AutovalidateMode.always,
               ),
             ),
           );
@@ -763,4 +763,57 @@ void main() {
     expect(currentValue, equals('one'));
     expect(find.text(currentValue), findsOneWidget);
   });
+
+  testWidgets('autovalidateMode is passed to super', (WidgetTester tester) async {
+    int _validateCalled = 0;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Center(
+            child: DropdownButtonFormField<String>(
+              autovalidateMode: AutovalidateMode.always,
+              items: menuItems.map((String value) {
+                return DropdownMenuItem<String>(
+                  value: value,
+                  child: Text(value),
+                );
+              }).toList(),
+              onChanged: onChanged,
+              validator: (String value) {
+                _validateCalled++;
+                return null;
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    expect(_validateCalled, 1);
+  });
+
+  testWidgets('autovalidateMode and autovalidate should not be used at the same time', (WidgetTester tester) async {
+    Widget builder() {
+      return MaterialApp(
+        home: Material(
+          child: Center(
+            child: DropdownButtonFormField<String>(
+              autovalidate: true,
+              autovalidateMode: AutovalidateMode.always,
+              items: menuItems.map((String value) {
+                return DropdownMenuItem<String>(
+                  value: value,
+                  child: Text(value),
+                );
+              }).toList(),
+              onChanged: onChanged,
+            ),
+          ),
+        ),
+      );
+    }
+    expect(() => builder(), throwsAssertionError);
+  });
+
 }

packages/flutter/test/material/dropdown_test.dart

@@ -2169,6 +2169,7 @@ void main() {
                       icon: Container(),
                       items: itemValues.map<DropdownMenuItem<String>>((String value) {
                         return DropdownMenuItem<String>(
+                          value: value,
                           child: Text(value),
                         );
                       }).toList(),

packages/flutter/test/material/text_form_field_test.dart

@@ -191,7 +191,7 @@ void main() {
     expect(_value, 'Soup');
   });
 
-  testWidgets('autovalidate is passed to super', (WidgetTester tester) async {
+  testWidgets('autovalidateMode is passed to super', (WidgetTester tester) async {
     int _validateCalled = 0;
 
     await tester.pumpWidget(
@@ -199,7 +199,7 @@ void main() {
         home: Material(
           child: Center(
             child: TextFormField(
-              autovalidate: true,
+              autovalidateMode: AutovalidateMode.always,
               validator: (String value) {
                 _validateCalled++;
                 return null;
@@ -225,7 +225,7 @@ void main() {
           child: Center(
             child: TextFormField(
               enabled: true,
-              autovalidate: true,
+              autovalidateMode: AutovalidateMode.always,
               validator: (String value) {
                 _validateCalled += 1;
                 return null;
@@ -444,4 +444,46 @@ void main() {
     final TextField widget = tester.widget(find.byType(TextField));
     expect(widget.autofillHints, equals(const <String>[AutofillHints.countryName]));
   });
+
+  testWidgets('autovalidateMode is passed to super', (WidgetTester tester) async {
+    int _validateCalled = 0;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Material(
+          child: Scaffold(
+            body: TextFormField(
+              autovalidateMode: AutovalidateMode.onUserInteraction,
+              validator: (String value) {
+                _validateCalled++;
+                return null;
+              },
+            ),
+          ),
+        ),
+      ),
+    );
+
+    expect(_validateCalled, 0);
+    await tester.enterText(find.byType(TextField), 'a');
+    await tester.pump();
+    expect(_validateCalled, 1);
+  });
+
+  testWidgets('autovalidateMode and autovalidate should not be used at the same time', (WidgetTester tester) async {
+    expect(() async {
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Material(
+            child: Scaffold(
+              body: TextFormField(
+                autovalidate: true,
+                autovalidateMode: AutovalidateMode.onUserInteraction,
+              ),
+            ),
+          ),
+        ),
+      );
+      }, throwsAssertionError);
+  });
 }

packages/flutter/test/widgets/form_test.dart

@@ -89,7 +89,7 @@ void main() {
     final GlobalKey<FormState> formKey = GlobalKey<FormState>();
     String errorText(String value) => value + '/error';
 
-    Widget builder(bool autovalidate) {
+    Widget builder(AutovalidateMode autovalidateMode) {
       return MaterialApp(
         home: MediaQuery(
           data: const MediaQueryData(devicePixelRatio: 1.0),
@@ -99,7 +99,7 @@ void main() {
               child: Material(
                 child: Form(
                   key: formKey,
-                  autovalidate: autovalidate,
+                  autovalidateMode: autovalidateMode,
                   child: TextFormField(
                     validator: errorText,
                   ),
@@ -112,11 +112,11 @@ void main() {
     }
 
     // Start off not autovalidating.
-    await tester.pumpWidget(builder(false));
+    await tester.pumpWidget(builder(AutovalidateMode.disabled));
 
     Future<void> checkErrorText(String testValue) async {
       formKey.currentState.reset();
-      await tester.pumpWidget(builder(false));
+      await tester.pumpWidget(builder(AutovalidateMode.disabled));
       await tester.enterText(find.byType(TextFormField), testValue);
       await tester.pump();
 
@@ -128,7 +128,7 @@ void main() {
 
       // Try again with autovalidation. Should validate immediately.
       formKey.currentState.reset();
-      await tester.pumpWidget(builder(true));
+      await tester.pumpWidget(builder(AutovalidateMode.always));
       await tester.enterText(find.byType(TextFormField), testValue);
       await tester.pump();
 
@@ -160,13 +160,13 @@ void main() {
                         key: fieldKey1,
                         initialValue: validString,
                         validator: validator,
-                        autovalidate: true
+                        autovalidateMode: AutovalidateMode.always,
                       ),
                       TextFormField(
                         key: fieldKey2,
                         initialValue: validString,
                         validator: validator,
-                        autovalidate: true
+                        autovalidateMode: AutovalidateMode.always,
                       ),
                     ],
                   ),
@@ -207,13 +207,13 @@ void main() {
                           key: fieldKey1,
                           initialValue: validString,
                           validator: validator,
-                          autovalidate: false,
+                          autovalidateMode: AutovalidateMode.disabled,
                         ),
                         TextFormField(
                           key: fieldKey2,
                           initialValue: '',
                           validator: validator,
-                          autovalidate: false,
+                          autovalidateMode: AutovalidateMode.disabled,
                         ),
                       ],
                     ),
@@ -249,7 +249,7 @@ void main() {
               child: Material(
                 child: Form(
                   key: formKey,
-                  autovalidate: true,
+                  autovalidateMode: AutovalidateMode.always,
                   child: ListView(
                     children: <Widget>[
                       TextFormField(
@@ -580,4 +580,273 @@ void main() {
     formKey.currentState.save();
     expect(formKey.currentState.validate(), isTrue);
   });
+
+  testWidgets('Does not auto-validate before value changes when autovalidateMode is set to onUserInteraction', (WidgetTester tester) async {
+    FormFieldState<String> formFieldState;
+
+    String errorText(String value) => '$value/error';
+
+    Widget builder() {
+      return MaterialApp(
+        home: MediaQuery(
+          data: const MediaQueryData(devicePixelRatio: 1.0),
+          child: Directionality(
+            textDirection: TextDirection.ltr,
+            child: Center(
+              child: Material(
+                child: FormField<String>(
+                  initialValue: 'foo',
+                  autovalidateMode: AutovalidateMode.onUserInteraction,
+                  builder: (FormFieldState<String> state) {
+                    formFieldState = state;
+                    return Container();
+                  },
+                  validator: errorText,
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(builder());
+    // The form field has no error.
+    expect(formFieldState.hasError, isFalse);
+    // No error widget is visible.
+    expect(find.text(errorText('foo')), findsNothing);
+  });
+
+  testWidgets('auto-validate before value changes if autovalidateMode was set to always', (WidgetTester tester) async {
+    FormFieldState<String> formFieldState;
+
+    String errorText(String value) => '$value/error';
+
+    Widget builder() {
+      return MaterialApp(
+        home: MediaQuery(
+          data: const MediaQueryData(devicePixelRatio: 1.0),
+          child: Directionality(
+            textDirection: TextDirection.ltr,
+            child: Center(
+              child: Material(
+                child: FormField<String>(
+                  initialValue: 'foo',
+                  autovalidateMode: AutovalidateMode.always,
+                  builder: (FormFieldState<String> state) {
+                    formFieldState = state;
+                    return Container();
+                  },
+                  validator: errorText,
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(builder());
+    expect(formFieldState.hasError, isTrue);
+  });
+
+  testWidgets('Form auto-validates form fields only after one of them changes if autovalidateMode is onUserInteraction', (WidgetTester tester) async {
+    const String initialValue = 'foo';
+    String errorText(String value) => 'error/$value';
+
+    Widget builder() {
+      return MaterialApp(
+        home: Directionality(
+          textDirection: TextDirection.ltr,
+          child: Center(
+            child: Material(
+              child: Form(
+                autovalidateMode: AutovalidateMode.onUserInteraction,
+                child: Column(
+                  children: <Widget>[
+                    TextFormField(
+                      initialValue: initialValue,
+                      validator: errorText,
+                    ),
+                    TextFormField(
+                      initialValue: initialValue,
+                      validator: errorText,
+                    ),
+                    TextFormField(
+                      initialValue: initialValue,
+                      validator: errorText,
+                    )
+                  ],
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    // Makes sure the Form widget won't autovalidate the form fields
+    // after rebuilds if there is not user interaction.
+    await tester.pumpWidget(builder());
+    await tester.pumpWidget(builder());
+
+    // We expect no validation error text being shown.
+    expect(find.text(errorText(initialValue)), findsNothing);
+
+    // Set a empty string into the first form field to
+    // trigger the fields validators.
+    await tester.enterText(find.byType(TextFormField).first, '');
+    await tester.pump();
+
+    // Now we expect the errors to be shown for the first Text Field and
+    // for the next two form fields that have their contents unchanged.
+    expect(find.text(errorText('')), findsOneWidget);
+    expect(find.text(errorText(initialValue)), findsNWidgets(2));
+  });
+
+  testWidgets('Form auto-validates form fields even before any have changed if autovalidateMode is set to always', (WidgetTester tester) async {
+    String errorText(String value) => 'error/$value';
+
+    Widget builder() {
+      return MaterialApp(
+        home: Directionality(
+          textDirection: TextDirection.ltr,
+          child: Center(
+            child: Material(
+              child: Form(
+                autovalidateMode: AutovalidateMode.always,
+                child: TextFormField(
+                  validator: errorText,
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    // The issue only happens on the second build so we
+    // need to rebuild the tree twice.
+    await tester.pumpWidget(builder());
+    await tester.pumpWidget(builder());
+
+    // We expect validation error text being shown.
+    expect(find.text(errorText('')), findsOneWidget);
+  });
+
+  testWidgets('autovalidate parameter is still used if true', (WidgetTester tester) async {
+    FormFieldState<String> formFieldState;
+    String errorText(String value) => '$value/error';
+
+    Widget builder() {
+      return MaterialApp(
+        home: MediaQuery(
+          data: const MediaQueryData(devicePixelRatio: 1.0),
+          child: Directionality(
+            textDirection: TextDirection.ltr,
+            child: Center(
+              child: Material(
+                child: FormField<String>(
+                  initialValue: 'foo',
+                  autovalidate: true,
+                  builder: (FormFieldState<String> state) {
+                    formFieldState = state;
+                    return Container();
+                  },
+                  validator: errorText,
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(builder());
+    expect(formFieldState.hasError, isTrue);
+  });
+
+  testWidgets('Form.reset() resets form fields, and auto validation will only happen on the next user interaction if autovalidateMode is onUserInteraction', (WidgetTester tester) async {
+    final GlobalKey<FormState> formState = GlobalKey<FormState>();
+    String errorText(String value) => '$value/error';
+
+    Widget builder() {
+      return MaterialApp(
+        theme: ThemeData(),
+        home: MediaQuery(
+          data: const MediaQueryData(devicePixelRatio: 1.0),
+          child: Directionality(
+            textDirection: TextDirection.ltr,
+            child: Center(
+              child: Form(
+                key: formState,
+                autovalidateMode: AutovalidateMode.onUserInteraction,
+                child: Material(
+                  child: TextFormField(
+                    initialValue: 'foo',
+                    validator: errorText,
+                  ),
+                ),
+              ),
+            ),
+          ),
+        ),
+      );
+    }
+
+    await tester.pumpWidget(builder());
+
+    // No error text is visible yet.
+    expect(find.text(errorText('foo')), findsNothing);
+
+    await tester.enterText(find.byType(TextFormField), 'bar');
+    await tester.pumpAndSettle();
+    await tester.pump();
+    expect(find.text(errorText('bar')), findsOneWidget);
+
+    // Resetting the form state should remove the error text.
+    formState.currentState.reset();
+    await tester.pump();
+    expect(find.text(errorText('bar')), findsNothing);
+  });
+
+  testWidgets('Form.autovalidateMode and Form.autovalidate should not be used at the same time', (WidgetTester tester) async {
+    Widget builder() {
+      return MaterialApp(
+        home: MediaQuery(
+          data: const MediaQueryData(devicePixelRatio: 1.0),
+          child: Directionality(
+            textDirection: TextDirection.ltr,
+            child: Form(
+              autovalidate: true,
+              autovalidateMode: AutovalidateMode.disabled,
+              child: Container(),
+            ),
+          ),
+        ),
+      );
+    }
+    expect(() => builder(), throwsAssertionError);
+  });
+
+  testWidgets('FormField.autovalidateMode and FormField.autovalidate should not be used at the same time', (WidgetTester tester) async {
+    Widget builder() {
+      return MaterialApp(
+        home: MediaQuery(
+          data: const MediaQueryData(devicePixelRatio: 1.0),
+          child: Directionality(
+            textDirection: TextDirection.ltr,
+            child: FormField<String>(
+              autovalidate: true,
+              autovalidateMode: AutovalidateMode.disabled,
+              builder: (_) {
+                return Container();
+              },
+            ),
+          ),
+        ),
+      );
+    }
+    expect(() => builder(), throwsAssertionError);
+  });
 }