Puppet Specific Facts

=====================

Facter is meant to stand alone and apart from Puppet.  However, Facter often

runs inside Puppet and all custom facts included in the stdlib module will

almost always be evaluated in the context of Puppet and Facter working

together.

Still, we don't want to write custom facts that blow up in the users face if

Puppet is not loaded in memory.  This is often the case if the user runs

`facter` without also supplying the `--puppet` flag.

Ah! But Jeff, the custom fact won't be in the `$LOAD_PATH` unless the user

supplies `--facter`! You might say...

Not (always) true I say!  If the user happens to have a CWD of

`<modulepath>/stdlib/lib` then the facts will automatically be evaluated and

blow up.

In any event, it's pretty easy to write a fact that has no value if Puppet is

not loaded.  Simply do it like this:

    Facter.add(:node_vardir) do

      setcode do

        # This will be nil if Puppet is not available.

        Facter::Util::PuppetSettings.with_puppet do

          Puppet[:vardir]

        end

      end

    end

The `Facter::Util::PuppetSettings.with_puppet` method accepts a block and

yields to it only if the Puppet library is loaded.  If the Puppet library is

not loaded, then the method silently returns `nil` which Facter interprets as

an undefined fact value.  The net effect is that the fact won't be set.