Allow adding single key to hashes

This patch allow this syntax:
$hash[mykey] = 12

If the key already exist an error is raised. Hashes are essentially
write only, like puppet variables.

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

2 files changed, 31 insertions, 8 deletions

diff --git a/lib/puppet/parser/ast/leaf.rb b/lib/puppet/parser/ast/leaf.rb
index 206ea5cbe..0f427ef37 100644
--- a/lib/puppet/parser/ast/leaf.rb
+++ b/lib/puppet/parser/ast/leaf.rb
@@ -142,17 +142,36 @@ class Puppet::Parser::AST
     class HashOrArrayAccess < AST::Leaf
         attr_accessor :variable, :key
 
-        def evaluate(scope)
+        def evaluate_container(scope)
             container = variable.respond_to?(:evaluate) ? variable.safeevaluate(scope) : variable
-            object = (container.is_a?(Hash) or container.is_a?(Array)) ? container : scope.lookupvar(container)
+            (container.is_a?(Hash) or container.is_a?(Array)) ? container : scope.lookupvar(container)
+        end
 
-            accesskey = key.respond_to?(:evaluate) ? key.safeevaluate(scope) : key
+        def evaluate_key(scope)
+            key.respond_to?(:evaluate) ? key.safeevaluate(scope) : key
+        end
+
+        def evaluate(scope)
+            object = evaluate_container(scope)
 
             unless object.is_a?(Hash) or object.is_a?(Array)
                 raise Puppet::ParseError, "#{variable} is not an hash or array when accessing it with #{accesskey}"
             end
 
-            return object[accesskey]
+            return object[evaluate_key(scope)]
+        end
+
+        # Assign value to this hashkey or array index
+        def assign(scope, value)
+            object = evaluate_container(scope)
+            accesskey = evaluate_key(scope)
+
+            if object.is_a?(Hash) and object.include?(accesskey)
+                raise Puppet::ParseError, "Assigning to the hash '#{variable}' with an existing key '#{accesskey}' is forbidden"
+            end
+
+            # assign to hash or array
+            object[accesskey] = value
         end
 
         def to_s
diff --git a/lib/puppet/parser/ast/vardef.rb b/lib/puppet/parser/ast/vardef.rb
index ae24b3233..f103d49c3 100644
--- a/lib/puppet/parser/ast/vardef.rb
+++ b/lib/puppet/parser/ast/vardef.rb
@@ -13,11 +13,15 @@ class Puppet::Parser::AST
         # Look up our name and value, and store them appropriately.  The
         # lexer strips off the syntax stuff like '$'.
         def evaluate(scope)
-            name = @name.safeevaluate(scope)
             value = @value.safeevaluate(scope)
-
-            parsewrap do
-                scope.setvar(name,value, :file => @file, :line => @line, :append => @append)
+            if name.is_a?(HashOrArrayAccess)
+                name.assign(scope, value)
+            else
+                name = @name.safeevaluate(scope)
+
+                parsewrap do
+                    scope.setvar(name,value, :file => @file, :line => @line, :append => @append)
+                end
             end
         end