(#13610) Add is_function_available to stdlib

This function provides a simple wrapper around
Puppet::Parser::Functions.function for access within Puppet manifests.
This will allow users to check whether or not a plugin or functionality
such as hiera is installed on the server.

1 files changed, 23 insertions, 0 deletions

diff --git a/lib/puppet/parser/functions/is_function_available.rb b/lib/puppet/parser/functions/is_function_available.rb
new file mode 100644
index 0000000..6cbd35c
--- /dev/null
+++ b/lib/puppet/parser/functions/is_function_available.rb
@@ -0,0 +1,23 @@
+#
+# is_function_available.rb
+#
+
+module Puppet::Parser::Functions
+  newfunction(:is_function_available, :type => :rvalue, :doc => <<-EOS
+This function accepts a string as an argument, determines whether the
+Puppet runtime has access to a function by that name.  It returns a
+true if the function exists, false if not.
+    EOS
+  ) do |arguments|
+
+    if (arguments.size != 1) then
+      raise(Puppet::ParseError, "is_function_available?(): Wrong number of arguments "+
+        "given #{arguments.size} for 1")
+    end
+
+    function = Puppet::Parser::Functions.function(arguments[0].to_sym)
+    function.is_a?(String) and not function.empty?
+  end
+end
+
+# vim: set ts=2 sw=2 et :