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-rw-r--r--puppet/modules/stdlib/lib/puppet/parser/functions/pick_default.rb35
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diff --git a/puppet/modules/stdlib/lib/puppet/parser/functions/pick_default.rb b/puppet/modules/stdlib/lib/puppet/parser/functions/pick_default.rb
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+++ b/puppet/modules/stdlib/lib/puppet/parser/functions/pick_default.rb
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+module Puppet::Parser::Functions
+ newfunction(:pick_default, :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). If no value is
+found, it will return the last argument.
+
+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:
+
+ $real_jenkins_version = pick_default($::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.
+
+Note that, contrary to the pick() function, the pick_default does not fail if
+all arguments are empty. This allows pick_default to use an empty value as
+default.
+
+EOS
+) do |args|
+ fail "Must receive at least one argument." if args.empty?
+ default = args.last
+ args = args[0..-2].compact
+ args.delete(:undef)
+ args.delete(:undefined)
+ args.delete("")
+ args << default
+ return args[0]
+ end
+end