What is the outcome if a class name starts with an underscore?

If a class name in Puppet starts with an underscore, it is treated as a private class. This means it cannot be declared or included in the same way as public classes. As a result, if you attempt to use or reference a class with a leading underscore in contexts where its visibility is restricted, Puppet throws an error, causing the compilation to fail.

By convention in Puppet, class names that start with an underscore are meant for internal use and are not intended to be directly referenced outside of their defining module. This encapsulation helps maintain clean and organized code, ensuring that certain classes are not unintentionally exposed to other parts of the manifest, which could lead to unexpected behaviors or conflicts. Thus, the compilation failure is a direct consequence of violating these design principles.