Allow delayed attribute evaluation. Add tests for delayed evaluation

2 files changed, 44 insertions, 8 deletions

diff --git a/chef/lib/chef/mixin/params_validate.rb b/chef/lib/chef/mixin/params_validate.rb
index 649224f978..4266e69580 100644
--- a/chef/lib/chef/mixin/params_validate.rb
+++ b/chef/lib/chef/mixin/params_validate.rb
@@ -16,7 +16,8 @@
 # limitations under the License.
 
 class Chef
-  
+  class DelayedEvaluator < Proc
+  end
   module Mixin
     module ParamsValidate
       
@@ -75,18 +76,32 @@ class Chef
         end
         opts
       end
-          
-      def set_or_return(symbol, arg, validation)
+      
+      def delay_eval(&block)
+        DelayedEvaluator.new(&block)
+      end
+
+      def set_or_return(symbol, arg, validation, &block)
         iv_symbol = "@#{symbol.to_s}".to_sym
         map = {
           symbol => validation
         }
-
-        if arg == nil && self.instance_variable_defined?(iv_symbol) == true
-          self.instance_variable_get(iv_symbol)
+        if arg == nil && self.instance_variable_defined?(iv_symbol) == true && !block_given?
+          ivar = self.instance_variable_get(iv_symbol)
+          if(ivar.is_a?(DelayedEvaluator))
+            validate({ symbol => ivar.call }, { symbol => validation })[symbol]
+          else
+            ivar
+          end
         else
-          opts = validate({ symbol => arg }, { symbol => validation })
-          self.instance_variable_set(iv_symbol, opts[symbol])
+          if(arg.is_a?(DelayedEvaluator))
+            val = arg
+          elsif(block_given?)
+            val = DelayedEvaluator.new(&block)
+          else
+            val = validate({ symbol => arg }, { symbol => validation })[symbol]
+          end
+          self.instance_variable_set(iv_symbol, val)
         end
       end
             
diff --git a/chef/spec/unit/mixin/params_validate_spec.rb b/chef/spec/unit/mixin/params_validate_spec.rb
index dd0366c37c..25c0c17f1e 100644
--- a/chef/spec/unit/mixin/params_validate_spec.rb
+++ b/chef/spec/unit/mixin/params_validate_spec.rb
@@ -366,5 +366,26 @@ describe Chef::Mixin::ParamsValidate do
     @vo.set_or_return(:name, value, { }).object_id.should == value.object_id
     @vo.set_or_return(:foo, nil, { :name_attribute => true }).object_id.should == value.object_id
   end
+
+  it "should allow DynamicEvaluator instance to be set for value regardless of restriction" do
+    value = Chef::DelayedEvaluator.new{ 'test' }
+    @vo.set_or_return(:test, value, {:kind_of => String})
+    @vo.set_or_return(:test, nil, {:kind_of => String}).should == 'test'
+  end
+
+  it "should raise an error when evaluated attribute is not valid" do
+    value = Chef::DelayedEvaluator.new{ 'test' }
+    @vo.set_or_return(:test, value, {:kind_of => Numeric})
+    lambda do
+      @vo.set_or_return(:test, nil, {:kind_of => Numeric})
+    end.should raise_error(Chef::Exceptions::ValidationFailed)
+  end
+
+  it "should not evaluate non DelayedEvaluator instances" do
+    value = lambda{ 'test' }
+    @vo.set_or_return(:test, value, {})
+    @vo.set_or_return(:test, nil, {}).object_id.should == value.object_id
+    @vo.set_or_return(:test, nil, {}).should be_a(Proc)
+  end
   
 end