What steps will reproduce the problem?
1. define message with a field with default value.
2. populate a builder of that message, but don't set that field.
3. observe that json doesn't contain default value.
What is the expected output? What do you see instead?
should contain that field, but with default value set.
What version of the product are you using? On what operating system?
version 1.2, on a mac.
Please provide any additional information below.