Fix #3907 - Hash couldn't be initialized with an empty hash

The following manifest was failing:
$data = {}

This patch makes sure we initalize our ast hash with an empty ruby
hash when it is created without any values.

Signed-off-by: Brice Figureau <brice-puppet@daysofwonder.com>

2 files changed, 17 insertions, 0 deletions

diff --git a/lib/puppet/parser/ast/asthash.rb b/lib/puppet/parser/ast/asthash.rb
index aa5127dd9..d04901912 100644
--- a/lib/puppet/parser/ast/asthash.rb
+++ b/lib/puppet/parser/ast/asthash.rb
@@ -28,5 +28,10 @@ class Puppet::Parser::AST
         def to_s
             "{" + @value.collect { |v| v.collect { |a| a.to_s }.join(' => ') }.join(', ') + "}"
         end
+
+        def initialize(args)
+            super(args)
+            @value ||= {}
+        end
     end
 end
diff --git a/spec/unit/parser/ast/asthash.rb b/spec/unit/parser/ast/asthash.rb
index c6839ab4d..fc8e1c7ea 100644
--- a/spec/unit/parser/ast/asthash.rb
+++ b/spec/unit/parser/ast/asthash.rb
@@ -78,6 +78,18 @@ describe Puppet::Parser::AST::ASTHash do
         operator.evaluate(@scope).should == { key1 => "b", key2 => "d" }
     end
 
+    describe "when being initialized without arguments" do
+        it "should evaluate to an empty hash" do
+            hash = Puppet::Parser::AST::ASTHash.new({})
+            hash.evaluate(@scope).should == {}
+        end
+
+        it "should support merging" do
+            hash = Puppet::Parser::AST::ASTHash.new({})
+            hash.merge({"a" => "b"}).should == {"a" => "b"}
+        end
+    end
+
     it "should return a valid string with to_s" do
         hash = Puppet::Parser::AST::ASTHash.new(:value => { "a" => "b", "c" => "d" })