Feat: form field programmatic errors

lib/src/components/date_picker.dart

@@ -1162,7 +1162,8 @@ class _ShadDatePickerState extends State<ShadDatePicker> {
         );
       },
       child: ShadButton.raw(
-        decoration: widget.buttonDecoration,
+        decoration:
+            widget.buttonDecoration ?? theme.datePickerTheme.buttonDecoration,
         variant: widget.buttonVariant ??
             theme.datePickerTheme.buttonVariant ??
             ShadButtonVariant.outline,

lib/src/components/form/field.dart

@@ -134,6 +134,7 @@ class ShadFormBuilderField<T> extends FormField<T> {
 /// form.
 class ShadFormBuilderFieldState<F extends ShadFormBuilderField<T>, T>
     extends FormFieldState<T> {
+  String? _customErrorText;
   FocusNode? _focusNode;
   ShadFormState? _parentForm;
 
@@ -156,6 +157,28 @@ class ShadFormBuilderFieldState<F extends ShadFormBuilderField<T>, T>
   /// Whether the field is enabled, factoring in parent form state.
   bool get enabled => widget.enabled && (_parentForm?.enabled ?? true);
 
+  @override
+
+  /// Returns the current error text,
+  /// As it might be validation error or programmatically set.
+  String? get errorText => super.errorText ?? _customErrorText;
+
+  @override
+
+  /// Returns `true` if the field has an error or has a custom error text.
+  bool get hasError => super.hasError || errorText != null;
+
+  @override
+
+  /// Returns `true` if the field is valid and has no custom error text.
+  bool get isValid => super.isValid && _customErrorText == null;
+
+  /// Returns `true` if the field's value is valid and ignores custom error.
+  bool get valueIsValid => super.isValid;
+
+  /// Returns `true` if the field has an error and ignores custom error.
+  bool get valueHasError => super.hasError;
+
   @override
   void initState() {
     super.initState();
@@ -197,9 +220,40 @@ class ShadFormBuilderFieldState<F extends ShadFormBuilderField<T>, T>
   void reset() {
     super.reset();
     didChange(initialValue);
+    if (_customErrorText != null) {
+      setState(() => _customErrorText = null);
+    }
     widget.onReset?.call();
   }
 
+  /// Validate field
+  ///
+  /// Clear custom error if [clearCustomError] is `true`.
+  /// By default `true`
+  ///
+  @override
+  bool validate({
+    bool clearCustomError = true,
+  }) {
+    if (clearCustomError && _customErrorText != null) {
+      setState(() => _customErrorText = null);
+    }
+    final isValid = super.validate() && !hasError;
+    return isValid;
+  }
+
+  /// Invalidate field with a [errorText]
+  ///
+  void invalidate(String errorText, {bool revalidate = true}) {
+    setState(() => _customErrorText = errorText);
+
+    if (revalidate) {
+      validate(
+        clearCustomError: false,
+      );
+    }
+  }
+
   @override
   void dispose() {
     if (widget.id != null) _parentForm?.unregisterField(widget.id!, this);

test/src/components/input_test.dart

@@ -2,6 +2,9 @@ import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:shadcn_ui/src/app.dart';
 import 'package:shadcn_ui/src/components/input.dart';
+import 'package:shadcn_ui/src/components/form/fields/input.dart';
+import 'package:shadcn_ui/src/components/form/form.dart';
+import 'package:shadcn_ui/src/components/form/field.dart';
 
 import '../../extra/pump_async_widget.dart';
 
@@ -24,5 +27,41 @@ void main() {
         matchesGoldenFile('goldens/input.png'),
       );
     });
+
+    testWidgets('ShadInputFormField programmatic error matches goldens',
+        (tester) async {
+      // Use a GlobalKey to access the field state and call invalidate
+      final key =
+          GlobalKey<ShadFormBuilderFieldState<ShadInputFormField, String>>();
+
+      await tester.pumpAsyncWidget(
+        createTestWidget(
+          ShadForm(
+            child: Padding(
+              padding: const EdgeInsets.all(16),
+              child: ShadInputFormField(
+                key: key,
+                label: const Text('Email'),
+                placeholder: const Text('Email'),
+              ),
+            ),
+          ),
+        ),
+      );
+
+      // Programmatically set an error on the field
+      key.currentState!.invalidate('This field is required');
+      await tester.pumpAndSettle();
+      // Sanity-check state to catch regressions beyond the golden image.
+      expect(key.currentState!.hasError, isTrue);
+      expect(key.currentState!.errorText, 'This field is required');
+      expect(key.currentState!.isValid, isFalse);
+      // Base value has no validator in this test, so valueIsValid should be true.
+      expect(key.currentState!.valueIsValid, isTrue);
+      expect(
+        find.byType(ShadInputFormField),
+        matchesGoldenFile('goldens/input_error.png'),
+      );
+    });
   });
 }