Represents a form error.

It can either be:

• RequiredFieldIsEmpty, meaning that a required field is empty.
• ValidationFailed, meaning the field validation has failed. This type of error contains a String describing the validation error.
• External, meaning the field has an external error that cannot be validated on the client. This mostly contains errors directly assigned to the field on form construction using the error attribute.

These type of errors are returned alongside each field in the Form.fill and Form.Base.fill functions.

You can easily write a simple function that turns this type into a String:

errorToString : Error -> String
errorToString error =
    case error of
        Error.RequiredFieldIsEmpty ->
            "this field is required"


        Error.ValidationFailed errorDescription ->
            errorDescription