lib/puppet/parser/functions/pick.rb


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module Puppet::Parser::Functions
 newfunction(:pick, :type => :rvalue, :doc => <<-EOS

This function is similar to a coalesce function in SQL in that it will return
the first value in a list of values that is not undefined or an empty string
(two things in Puppet that will return a boolean false value). Typically,
this function is used to check for a value in the Puppet Dashboard/Enterprise
Console, and failover to a default value like the following:

  $real_jenkins_version = pick($::jenkins_version, '1.449')

The value of $real_jenkins_version will first look for a top-scope variable
called 'jenkins_version' (note that parameters set in the Puppet Dashboard/
Enterprise Console are brought into Puppet as top-scope variables), and,
failing that, will use a default value of 1.449.

EOS
) do |args|
   args = args.compact
   args.delete(:undef)
   args.delete(:undefined)
   args.delete("")
   if args[0].to_s.empty? then
     fail "Must provide non empty value."
   else
     return args[0]
   end
 end
end