This is a Grails plugin that implements "recursive" message resolution. It extends the default message format placeholder handling to allow placeholders whose replacement strings are themselves looked up in the messageSource rather than simply inserted verbatim. The motivating use case is for domain class property names in validation messages:
default.blank.message={0,message,property.name.} must not be blank
property.name.firstName=First name
property.name.email=E-mail address
In this example, a domain class with a firstName property that is constrained to be non-blank would produce the error message "First name must not be blank".
The mechanism looks for message placeholders that consist of an argument index,
comma, "message", comma, and a prefix. When substituting a value v for the
placeholder the plugin will look up the message key prefix + v with no
arguments, and use the result of that lookup as the placeholder replacement.
If there is no message named prefix + v then v is used verbatim in the
normal way.