Error Messages for Constraints

[yuriy-fix]

Description

Enable developers to specify custom error messages for field component constraints (e.g., pattern, minimum length) using the i18n. These messages should be displayed when validation is run. Additionally, these messages should also be utilized by the Vaadin Binder to provide clear and consistent feedback to users during form validation.

Use cases

As a developer
I want to specify custom error messages for field component constraints using the i18n mechanism
So that I can ensure consistent and localized feedback for users when constraints are violated, including when using Vaadin Binder

As an end user filling out a form
I want to see clear and helpful error messages when I make a mistake
So that I can understand what went wrong and how to correct it quickly

Acceptance criteria

• Custom error messages can be set for constraints using explicit methods on the field's i18n. For example, datePicker.getI18n().setBadInputErrorMessage("Date has incorrect format").
• Custom error messages provided via i18n are displayed during validation when constraints are violated.
• Error messages provided through i18n are respected by Vaadin Binder during validation.

General criteria

• APIs reviewed

• Design

• Performance

• UX/DX tests in Alpha

• Documentation:

• How to test?

• Limitations:
• When used with Binder, the required constraint should be set on the Binder itself using asRequired, and the error message should be provided through it. The message set on the field's i18n won't be used in this case.