InputDecoration.error should activate error state (#134001)

When passed an `error` widget, `InputDecoration` should activate its error state. Before this change the `errorBorder` would only activate if an `errorText` was provided. This change solves this issue by accounting for a provided `error` widget.

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

@@ -1971,6 +1971,7 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
 
   TextAlign? get textAlign => widget.textAlign;
   bool get isFocused => widget.isFocused;
+  bool get _hasError => decoration.errorText != null || decoration.error != null;
   bool get isHovering => widget.isHovering && decoration.enabled;
   bool get isEmpty => widget.isEmpty;
   bool get _floatingLabelEnabled {
@@ -2011,7 +2012,7 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
           ? Colors.transparent
           : themeData.disabledColor;
     }
-    if (decoration.errorText != null) {
+    if (_hasError) {
       return themeData.colorScheme.error;
     }
     if (isFocused) {
@@ -2107,7 +2108,7 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
 
   TextStyle _getFloatingLabelStyle(ThemeData themeData, InputDecorationTheme defaults) {
     TextStyle defaultTextStyle = MaterialStateProperty.resolveAs(defaults.floatingLabelStyle!, materialState);
-    if (decoration.errorText != null && decoration.errorStyle?.color != null) {
+    if (_hasError && decoration.errorStyle?.color != null) {
       defaultTextStyle = defaultTextStyle.copyWith(color: decoration.errorStyle?.color);
     }
     defaultTextStyle = defaultTextStyle.merge(decoration.floatingLabelStyle ?? decoration.labelStyle);
@@ -2137,7 +2138,7 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
       if (!decoration.enabled) MaterialState.disabled,
       if (isFocused) MaterialState.focused,
       if (isHovering) MaterialState.hovered,
-      if (decoration.errorText != null) MaterialState.error,
+      if (_hasError) MaterialState.error,
     };
   }
 
@@ -2205,14 +2206,13 @@ class _InputDecoratorState extends State<InputDecorator> with TickerProviderStat
       ),
     );
 
-    final bool isError = decoration.errorText != null;
     InputBorder? border;
     if (!decoration.enabled) {
-      border = isError ? decoration.errorBorder : decoration.disabledBorder;
+      border = _hasError ? decoration.errorBorder : decoration.disabledBorder;
     } else if (isFocused) {
-      border = isError ? decoration.focusedErrorBorder : decoration.focusedBorder;
+      border = _hasError ? decoration.focusedErrorBorder : decoration.focusedBorder;
     } else {
-      border = isError ? decoration.errorBorder : decoration.enabledBorder;
+      border = _hasError ? decoration.errorBorder : decoration.enabledBorder;
     }
     border ??= _getDefaultBorder(themeData, defaults);
 

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

@@ -945,7 +945,7 @@ class _TextFieldState extends State<TextField> with RestorationMixin implements
 
   bool get _hasIntrinsicError => widget.maxLength != null && widget.maxLength! > 0 && _effectiveController.value.text.characters.length > widget.maxLength!;
 
-  bool get _hasError => widget.decoration?.errorText != null || _hasIntrinsicError;
+  bool get _hasError => widget.decoration?.errorText != null || widget.decoration?.error != null || _hasIntrinsicError;
 
   Color get _errorColor => widget.decoration?.errorStyle?.color ?? Theme.of(context).colorScheme.error;
 

packages/flutter/test/material/input_decorator_test.dart

@@ -1668,6 +1668,105 @@ void runAllTests({ required bool useMaterial3 }) {
     expect(find.text('errorText'), findsOneWidget);
   });
 
+  testWidgets('InputDecoration shows error border for errorText and error widget', (WidgetTester tester) async {
+    const InputBorder errorBorder = OutlineInputBorder(
+      borderSide: BorderSide(color: Colors.red, width: 1.5),
+    );
+    const InputBorder focusedErrorBorder = OutlineInputBorder(
+      borderSide: BorderSide(color: Colors.teal, width: 5.0),
+    );
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        useMaterial3: useMaterial3,
+        isFocused: true,
+        decoration: const InputDecoration(
+          errorText: 'error',
+          // enabled: true (default)
+          errorBorder: errorBorder,
+          focusedErrorBorder: focusedErrorBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // Border changes are animated.
+    expect(getBorder(tester), focusedErrorBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        useMaterial3: useMaterial3,
+        // isFocused: false (default)
+        decoration: const InputDecoration(
+          errorText: 'error',
+          // enabled: true (default)
+          errorBorder: errorBorder,
+          focusedErrorBorder: focusedErrorBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // Border changes are animated.
+    expect(getBorder(tester), errorBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        useMaterial3: useMaterial3,
+        // isFocused: false (default)
+        decoration: const InputDecoration(
+          errorText: 'error',
+          enabled: false,
+          errorBorder: errorBorder,
+          focusedErrorBorder: focusedErrorBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // Border changes are animated.
+    expect(getBorder(tester), errorBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        useMaterial3: useMaterial3,
+        isFocused: true,
+        decoration: const InputDecoration(
+          error: Text('error'),
+          // enabled: true (default)
+          errorBorder: errorBorder,
+          focusedErrorBorder: focusedErrorBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // Border changes are animated.
+    expect(getBorder(tester), focusedErrorBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        useMaterial3: useMaterial3,
+        // isFocused: false (default)
+        decoration: const InputDecoration(
+          error: Text('error'),
+          // enabled: true (default)
+          errorBorder: errorBorder,
+          focusedErrorBorder: focusedErrorBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // Border changes are animated.
+    expect(getBorder(tester), errorBorder);
+
+    await tester.pumpWidget(
+      buildInputDecorator(
+        useMaterial3: useMaterial3,
+        // isFocused: false (default)
+        decoration: const InputDecoration(
+          error: Text('error'),
+          enabled: false,
+          errorBorder: errorBorder,
+          focusedErrorBorder: focusedErrorBorder,
+        ),
+      ),
+    );
+    await tester.pumpAndSettle(); // Border changes are animated.
+    expect(getBorder(tester), errorBorder);
+  });
+
   testWidgetsWithLeakTracking('InputDecorator shows error widget', (WidgetTester tester) async {
     await tester.pumpWidget(
       buildInputDecorator(

packages/flutter/test/material/text_field_test.dart

@@ -787,6 +787,42 @@ void main() {
     expect(state.widget.cursorColor, cursorColor);
   });
 
+  testWidgets('Use error cursor color when an InputDecoration with an errorText or error widget is provided', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Material(
+          child: TextField(
+            autofocus: true,
+            decoration: InputDecoration(
+              error: Text('error'),
+              errorStyle: TextStyle(color: Colors.teal),
+            ),
+          ),
+        ),
+      ),
+    );
+    await tester.pump();
+    EditableTextState state = tester.state<EditableTextState>(find.byType(EditableText));
+    expect(state.widget.cursorColor, Colors.teal);
+
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Material(
+          child: TextField(
+            autofocus: true,
+            decoration: InputDecoration(
+              errorText: 'error',
+              errorStyle: TextStyle(color: Colors.teal),
+            ),
+          ),
+        ),
+      ),
+    );
+    await tester.pump();
+    state = tester.state<EditableTextState>(find.byType(EditableText));
+    expect(state.widget.cursorColor, Colors.teal);
+  });
+
   testWidgetsWithLeakTracking('sets cursorOpacityAnimates on EditableText correctly', (WidgetTester tester) async {
 
     // True