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.
This does a cleanup of the examples, removing all of the "section" markers and extra comments that we don't need anymore now that the samples are no longer in the source code. It also removes the --template arguments from the {@tool dartpad} and {@tool sample} directives, since those are no longer used. It converts two examples that I discovered were still embedded into linked examples in the examples folder.
I didn't delete the templates from the snippets config folder yet, because there are still embedded samples in the dart:ui package from the engine that use them. Once dart:ui no longer uses the templates, they can be removed.
I bumped the version of the snippets package to pick up a change that allows removal of the --template argument.
This extracts the sample code out from the API doc comments, and places them in separate files on disk, allowing running of the examples locally, testing them, and building of slightly larger examples.
