add array union function

lib/puppet/parser/functions/array_union.rb

@@ -0,0 +1,10 @@
+Puppet::Parser::Functions::newfunction(
+  :array_union,
+  :type => :rvalue,
+  :doc => "Unions two arrays
+
+    Example: array_union(['a','b'],['c']) -> ['a','b','c']"
+) do |args|
+  raise Puppet::ParseError, 'array_union() needs two arguments' if args.length != 2
+  args[0].to_a | args[1].to_a
+end

spec/unit/parser/functions/array_union.rb

@@ -0,0 +1,39 @@
+#! /usr/bin/env ruby
+
+require File.dirname(__FILE__) + '/../../../spec_helper'
+
+describe "the array_union function" do
+
+  before :each do
+    @scope = Puppet::Parser::Scope.new
+  end
+
+  it "should exist" do
+    Puppet::Parser::Functions.function("array_union").should == "function_array_union"
+  end
+
+  it "should raise a ParseError if there is less than 2 arguments" do
+    lambda { @scope.function_array_union([["foo"]]) }.should( raise_error(Puppet::ParseError))
+  end
+
+  it "should raise a ParseError if there is more than 2 arguments" do
+    lambda { @scope.function_array_union([["foo", "bar", "gazonk"]]) }.should( raise_error(Puppet::ParseError))
+  end
+
+  it "should union to arrays" do
+    result = @scope.function_array_union([['a','b'],['c']])
+    result.should(eql(['a','b','c']))
+  end
+
+  it "should do nothing if an item is present" do
+    result = @scope.function_array_union([['a','b'],['b']])
+    result.should(eql(['a','b']))
+  end
+
+  it "should leave the argument untouched" do
+    a = ['a','b']
+    result = @scope.function_array_union([a,['c']])
+    a.should(eql(['a','b']))
+  end
+
+end