The new Form, FormField auto-validation API

The previous auto validation API for the Form and FormField widgets didn't control when auto validation should occur. So the auto validation for these widgets always happened on first build when the widget was first visible to the user, and you weren't able to control when the auto validation should happen.

Due to the original API not allowing developers to change the auto validation behavior for validating only when the user interacts with the form field, we added new API that allows developers to configure how they want auto validation to behave for the Form and FormField widgets.

The following changes were made:

• The autovalidate parameter is deprecated.
• A new parameter called autovalidateMode, an Enum that accepts values from the AutovalidateMode Enum class, is added.

To migrate to the new auto validation API you need to replace the usage of the deprecated autovalidate parameter to the new autovalidateMode parameter. If you want the same behavior as before you can use: autovalidateMode = AutovalidateMode.always. This makes your Form and FormField widgets auto validate on first build and every time it changes.

Code before migration:

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return FormField(
      autovalidate: true,
      builder: (FormFieldState state) {
        return Container();
      },
    );
  }
}

Code after migration:

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return FormField(
      autovalidateMode: AutovalidateMode.always,
      builder: (FormFieldState state) {
        return Container();
      },
    );
  }
}

Landed in version: 1.21.0-5.0.pre
In stable release: 1.22

API documentation:

• AutovalidateMode

Relevant issues:

• Issue 56363
• Issue 18885
• Issue 15404
• Issue 36154
• Issue 48876

Relevant PRs:

• PR 56365: FormField should autovalidate only if its content was changed
• PR 59766: FormField should autovalidate only if its content was changed (fixed)

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