(PUP-3351) Evaluate ENC classes in the correct order

Without this patch classes declared from an ENC are evaluated in the
wrong order.  This is a problem because classes declared without
parameters are evaluated prior to classes with parameters which causes
an Error: Duplicate declaration when the classes with parameters are
evaluated.  According to the code comments for the
`evaluate_node_classes` method, the expected behavior is that classes
with an empty set of parameters will not conflict with classes that have
declared parameters.

Author: Jeff McCune

lib/puppet/parser/compiler.rb

@@ -187,9 +187,10 @@ def evaluate_node_classes
       classes_without_params = @node.classes
     end
 
-    evaluate_classes(classes_without_params, @node_scope || topscope)
-
+    # (PUP-3351) Avoid "Duplicate declaration" errors by evaluating classes
+    # with params prior to classes without params.
     evaluate_classes(classes_with_params, @node_scope || topscope)
+    evaluate_classes(classes_without_params, @node_scope || topscope)
   end
 
   # Evaluate each specified class in turn.  If there are any classes we can't

spec/unit/parser/compiler_spec.rb

@@ -422,6 +422,36 @@ def add_resource(name, parent = nil)
       @compiler.catalog.should be_vertex(resource)
     end
 
+    context 'and evaluating classes declared from an ENC' do
+      # Expected sequence of class evaluation
+      let(:seq) { sequence('partitioned_node_classes') }
+      # class { [c1, c0]: p1 => v1 }
+      let(:param_classes) do
+        { 'c1' => { 'p1' => 'v1' }, 'c0' => { 'p1' => 'v1' } }
+      end
+      # include 'c2'
+      let(:plain_classes) { { 'c2' => {} } }
+
+      let(:classes) { param_classes.merge(plain_classes) }
+
+      before :each do
+        # Stub _except_ evaluate_node_classes
+        compile_stub(:evaluate_node_classes)
+      end
+
+      it 'then evaluates classes declared with parameters before plain classes' do
+        @node.stubs(:classes).returns(classes)
+
+        [param_classes, plain_classes.keys].each do |partition|
+          @compiler.expects(:evaluate_classes).
+            with(partition, @compiler.topscope).
+            in_sequence(seq)
+        end
+
+        @compiler.compile
+      end
+    end
+
     it "should fail to add resources that conflict with existing resources" do
       path = make_absolute("/foo")
       file1 = resource(:file, path)