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authorMicah <micah@leap.se>2016-05-24 10:19:33 -0400
committerMicah <micah@leap.se>2016-05-24 10:19:33 -0400
commit0e9121a885d545e14488f9aec1a861ba90b7dbb2 (patch)
treee54275620f2ac3222d3c141ae97f73b423f91681 /puppet/modules/stdlib/README_DEVELOPER.markdown
parent40cfe3ca5f29428b237627d167f2405ea9193dbb (diff)
parent1da5dc55ee48fcd437f5b5df00a5b2f3991ec9f1 (diff)
Merge commit '1da5dc55ee48fcd437f5b5df00a5b2f3991ec9f1' as 'puppet/modules/stdlib'
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+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.