add hash_merge function

lib/puppet/parser/functions/hash_merge.rb

@@ -0,0 +1,10 @@
+Puppet::Parser::Functions::newfunction(
+  :hash_merge,
+  :type => :rvalue,
+  :doc => "Merges two hashes
+
+    Example: hash_merge({'a' => 1 ,'b' => 2},{'b' => 3, 'c' => 4}) -> {'a' => 1 ,'b' => 3, 'c' => 4}"
+) do |args|
+  raise Puppet::ParseError, 'hash_merge() needs two arguments' if args.length != 2
+  args[0].merge(args[1])
+end

spec/unit/parser/functions/hash_merge.rb

@@ -0,0 +1,34 @@
+#! /usr/bin/env ruby
+
+require File.dirname(__FILE__) + '/../../../spec_helper'
+
+describe "the hash_merge function" do
+
+  before :each do
+    @scope = Puppet::Parser::Scope.new
+  end
+
+  it "should exist" do
+    Puppet::Parser::Functions.function("hash_merge").should == "function_hash_merge"
+  end
+
+  it "should raise a ParseError if there is less than 2 arguments" do
+    lambda { @scope.function_hash_merge(["foo"]) }.should( raise_error(Puppet::ParseError))
+  end
+
+  it "should raise a ParseError if there is more than 2 arguments" do
+    lambda { @scope.function_hash_merge(["foo", "bar", "gazonk"]) }.should( raise_error(Puppet::ParseError))
+  end
+
+  it "should merge the two hashes" do
+    result = @scope.function_hash_merge([{'a' => 1 ,'b' => 2},{'b' => 3, 'c' => 4}])
+    result.should == {'a' => 1 ,'b' => 3, 'c' => 4}
+  end
+
+  it "should leave the argument untouched" do
+    a = {'a' => 1 ,'b' => 2}
+    result = @scope.function_hash_merge([{'a' => 1 ,'b' => 2},{'b' => 3, 'c' => 4}])
+    a.should == {'a' => 1 ,'b' => 2}
+  end
+
+end