Hasan M. Hallak f54dfcd27d
add forceErrorText to FormField & TextFormField. (#132903)
Introducing the `forceErrorText` property to both `FormField` and `TextFormField`. With this addition, we gain the capability to trigger an error state and provide an error message without invoking the `validator` method.

While the idea of making the `Validator` method work asynchronously may be appealing, it could introduce significant complexity to our current form field implementation. Additionally, this approach might not be suitable for all developers, as discussed by @justinmc  in this [comment](https://github.com/flutter/flutter/issues/56414#issuecomment-624960263).

This PR try to address this issue by adding `forceErrorText` property allowing us to force the error to the `FormField` or `TextFormField` at our own base making it possible to preform some async operations without the need for any hacks while keep the ability to check for errors if we call `formKey.currentState!.validate()`.

Here is an example:

<details> <summary>Code Example</summary>  

```dart
import 'package:flutter/material.dart';

void main() {
  runApp(
    const MaterialApp(home: MyHomePage()),
  );
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({
    super.key,
  });

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  final key = GlobalKey<FormState>();
  String? forcedErrorText;

  Future<void> handleValidation() async {
    // simulate some async work..
    await Future.delayed(const Duration(seconds: 3));

    setState(() {
      forcedErrorText = 'this username is not available.';
    });

    // wait for build to run and then check.
    //
    // this is not required though, as the error would already be showing.
    WidgetsBinding.instance.addPostFrameCallback((_) {
      print(key.currentState!.validate());
    });
  }

  @override
  Widget build(BuildContext context) {
    print('build');
    return Scaffold(
      floatingActionButton: FloatingActionButton(onPressed: handleValidation),
      body: Form(
        key: key,
        child: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Padding(
                padding: const EdgeInsets.symmetric(horizontal: 30),
                child: TextFormField(
                  forceErrorText: forcedErrorText,
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}
```
</details>

Related to #9688 & #56414.

Happy to hear your thoughts on this.
2024-06-18 17:52:21 +00:00
2024-06-17 17:26:08 +00:00
2024-06-17 17:26:08 +00:00
2024-06-13 14:58:16 +00:00

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