(PUP-638) Add a pick_default() function that always returns a value.

This version of pick() does not error out, instead always returning at least
the last argument, even if that too has no "real" value.

1 files changed, 35 insertions, 0 deletions

diff --git a/lib/puppet/parser/functions/pick_default.rb b/lib/puppet/parser/functions/pick_default.rb
new file mode 100644
index 0000000..36e33ab
--- /dev/null
+++ b/lib/puppet/parser/functions/pick_default.rb
@@ -0,0 +1,35 @@
+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