1 Puppet Specific Facts

     2 =====================

     3 

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

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

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

     7 together.

     8 

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

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

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

    12 

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

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

    15 

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

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

    18 blow up.

    19 

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

    21 not loaded.  Simply do it like this:

    22 

    23     Facter.add(:node_vardir) do

    24       setcode do

    25         # This will be nil if Puppet is not available.

    26         Facter::Util::PuppetSettings.with_puppet do

    27           Puppet[:vardir]

    28         end

    29       end

    30     end

    31 

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

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

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

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