1 files changed, 15 insertions, 0 deletions
diff --git a/join.rb b/join.rb
index b616e05..4522d23 100644
--- a/join.rb
+++ b/join.rb
@@ -7,11 +7,26 @@ module Puppet::Parser::Functions
     EOS
   ) do |arguments|
 
+    # Technically we support three arguments but only first two are mandatory ....
+    raise(Puppet::ParseError, "Wrong number of arguments " +
+      "given (#{arguments.size} for 2)") if arguments.size < 2
+
     array = arguments[0]
 
+    if not array.is_a?(Array)
+      raise(Puppet::ParseError, 'Requires an array to work with')
+    end
+
     suffix = arguments[1]
     prefix = arguments[2]
 
+    raise(Puppet::ParseError, 'You must provide suffix ' +
+      'to join array elements with') if suffix.empty?
+
+    if prefix and prefix.empty?
+      raise(Puppet::ParseError, 'You must provide prefix to add to join')
+    end
+
     if prefix and not prefix.empty?
       result = prefix + array.join(suffix + prefix)
     else