sourceafIoc::Contribute.fan

** Use in a module class to denote a service contribution method. The service to be contributed to 
** is derived from either the serviceId, serviceType, or the method name. 
** 
** Either 'serviceId' or 'serviceType' should be defined, not both. Or as a last resort, if neither 
** are given, the service id is derived from the method name, removing the prefix "contribute". 
** Though this latter approach is not re-factor safe.
facet class Contribute {

    ** The id of the service to be configured. 
    const Str?  serviceId   := null

    ** The type of the service to be configured. 
    const Type? serviceType := null

    ** Marks the contribution as optional; no Err is thrown if the service is not found. 
    ** 
    ** This allows you to contribute to services that may or may not be defined in the registry.
    ** (e.g. contributing to optional 3rd party library)
    const Bool  optional    := false
}