module Rake
class Promise NOT_SET = Object.new.freeze
attr_accessor :recorder
def initialize(args, &block)
@mutex = Mutex.new
@result = NOT_SET
@error = NOT_SET
@args = args.collect { |a| begin; a.dup; rescue; a; end }
@block = block
end
def value
unless complete?
stat :sleeping_on, :item_id => object_id
@mutex.synchronize do
stat :has_lock_on, :item_id => object_id
chore
stat :releasing_lock_on, :item_id => object_id
end
end
error? ? raise(@error) : @result
end
def work
stat :attempting_lock_on, :item_id => object_id
if @mutex.try_lock
stat :has_lock_on, :item_id => object_id
chore
stat :releasing_lock_on, :item_id => object_id
@mutex.unlock
else
stat :bailed_on, :item_id => object_id
end
end
private
def chore
if complete?
stat :found_completed, :item_id => object_id
return
end
stat :will_execute, :item_id => object_id
begin
@result = @block.call(*@args)
rescue Exception => e
@error = e
end
stat :did_execute, :item_id => object_id
discard
end
def result?
! @result.equal?(NOT_SET)
end
def error?
! @error.equal?(NOT_SET)
end
def complete?
result? || error?
end
def discard
@args = nil
@block = nil
end
def stat(*args)
@recorder.call(*args) if @recorder
end
end
end