[MESOS-2638] Add support for Optional parameters to protobuf handlers to wrap option fields

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: libprocess
• Assignee: Unassigned
• Reporter: Joris Van Remoortere
• Created: 20/Apr/15 20:50
• Updated: 19/Apr/16 01:05

Description

We currently don't have a way to install a protobuf handler for an option field where the handler takes an Optional parameter of the 'option' field in the protobuf message. The goal is to be able to do:

example

message Person {
  required string name = 1;
  option uint32_t age = 2; 
}

void person(const std::string& name, const Option<uint32_t>& age) 
{
  if (age.isSome()) { ... }
}

install<Person>(
    person, 
    &Person::name,
    &Person::age); 

We can then use this to test whether the field was provided, as opposed to capturing a reference to a default constructed value of the the type.

For now, the workaround is to use the take the entire message in the handler:

void person(const Person& person)
{
  if (person.has_age()) { ... }
}

install<Person>(person);