Merge pull request #843 from xuorig/print-type-duplicate-enum

Print Enum name when raising duplicate value error.

lib/graphql/enum_type.rb

@@ -94,7 +94,7 @@ def values=(new_values)
     # @param enum_value [EnumValue] A value to add to this type's set of values
     def add_value(enum_value)
       if @values_by_name.key?(enum_value.name)
-        raise "Enum value names must be unique. `#{enum_value.name}` already exists."
+        raise "Enum value names must be unique. Value `#{enum_value.name}` already exists on Enum `#{name}`."
       end
 
       @values_by_name[enum_value.name] = enum_value

spec/graphql/enum_type_spec.rb

@@ -113,9 +113,13 @@
 
   describe "validates enum value name uniqueness" do
     it "raises an exception when adding a duplicate enum value name" do
-      assert_raises "Enum value names must be unique. `COW` already exists." do
+      expected_message = "Enum value names must be unique. Value `COW` already exists on Enum `DairyAnimal`."
+
+      exception = assert_raises do
         enum.add_value(GraphQL::EnumType::EnumValue.define(name: "COW"))
       end
+
+      assert_equal(expected_message, exception.message)
     end
   end
 end