Prototype API for setting error messages through i18n and overloads [3 days]

[vursen]

Let's prototype API for setting error messages through i18n and overloads. Below are some examples of how it's supposed to look like.

Example 1 (setting error message through i18n objects):

datePicker.setMin(minDate);
datePicker.getI18n().setBadInputErrorMessage("Date has incorrect format");
datePicker.getI18n().getBadInputErrorMessage();
datePicker.getI18n().setMinErrorMessage("Date must be later than " + minDate);
datePicker.getI18n().getMinErrorMessage();

Example 2 (setting error messages through constraint method overloads) see #6280 (comment)

// These are just aliases for the corresponding i18n methods.
datePicker.setMin(minDate, "Date must be earlier than " + minDate);
datePicker.setMax(maxDate, "Date must be later than " + maxDate);

Example 3 (cross-field validation with Binder):

datePicker.setMin(minDate);
datePicker.getI18n().setBadInputErrorMessage("Date has incorrect format");
datePicker.getI18n().setMinErrorMessage("Date must be later than " + minDate);

binder.forField(datePicker)
        // Disable the default validator
	.withDefaultValidator(false)
        // Add a custom validator
	.withValidator(dateOrAnotherFieldPredicate, "You must fill either one field or another") 
        // Add the default validator manually. It will use error messages from the i18n object
	.withValidator(datePicker.getDefaultValidator()) 

Additional context

• Error messages for constraints #4618
• https://github.com/orgs/vaadin/discussions/4664

[knoobie]

I personally would love to have the option to have setMin(LocalDate min, ErrorMessageProvider errorMessageProvider) instead of the i18n object for full flexibility. https://vaadin.com/api/platform/current/com/vaadin/flow/data/binder/ErrorMessageProvider.html

[vursen]

I personally would love to have the option to have setMin(LocalDate min, ErrorMessageProvider errorMessageProvider) instead of the i18n object for full flexibility.

After some prototyping, we decided to postpone introducing constraint method overloads. Implementing them now through i18n would require a breaking change later to support ErrorMessageProvider. We plan to revisit this when the Flow components fully integrate with the new i18n mechanism to explore other alternatives.

[vursen]

Here are prototypes for TextField and NumberField:

• https://github.com/vaadin/flow-components/compare/proto/text-field/error-messages?expand=1
• https://github.com/vaadin/flow-components/compare/proto/number-field/error-messages?expand=1
• https://github.com/vaadin/flow-components/compare/proto/date-time-picker/i18n-error-messages?expand=1