From 68e94450a06e043ecf58ede565060f41b61043f9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Coutable?= <remy@rymai.me>
Date: Tue, 24 Jan 2017 17:07:56 +0100
Subject: [PATCH] Raise Gitlab::View::Presenter::CannotOverrideMethodError if
 presentee already respond to method
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Signed-off-by: Rémy Coutable <remy@rymai.me>
---
 lib/gitlab/view/presenter/base.rb                | 2 ++
 lib/gitlab/view/presenter/delegated.rb           | 6 ++++--
 spec/lib/gitlab/view/presenter/delegated_spec.rb | 7 +++----
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/lib/gitlab/view/presenter/base.rb b/lib/gitlab/view/presenter/base.rb
index 83c8ba5c1cf..dbfe0941e4d 100644
--- a/lib/gitlab/view/presenter/base.rb
+++ b/lib/gitlab/view/presenter/base.rb
@@ -1,6 +1,8 @@
 module Gitlab
   module View
     module Presenter
+      CannotOverrideMethodError = Class.new(StandardError)
+
       module Base
         extend ActiveSupport::Concern
 
diff --git a/lib/gitlab/view/presenter/delegated.rb b/lib/gitlab/view/presenter/delegated.rb
index fd90f7c2bad..387ff0f5d43 100644
--- a/lib/gitlab/view/presenter/delegated.rb
+++ b/lib/gitlab/view/presenter/delegated.rb
@@ -8,9 +8,11 @@ module Gitlab
           @subject = subject
 
           attributes.each do |key, value|
-            unless subject.respond_to?(key)
-              define_singleton_method(key) { value }
+            if subject.respond_to?(key)
+              raise CannotOverrideMethodError.new("#{subject} already respond to #{key}!")
             end
+
+            define_singleton_method(key) { value }
           end
 
           super(subject)
diff --git a/spec/lib/gitlab/view/presenter/delegated_spec.rb b/spec/lib/gitlab/view/presenter/delegated_spec.rb
index 8390188bfdc..e9d4af54389 100644
--- a/spec/lib/gitlab/view/presenter/delegated_spec.rb
+++ b/spec/lib/gitlab/view/presenter/delegated_spec.rb
@@ -17,10 +17,9 @@ describe Gitlab::View::Presenter::Delegated do
       expect(presenter.current_user).to eq('Jane Doe')
     end
 
-    it 'does not override the presentee attributes' do
-      presenter = presenter_class.new(project, user: 'Jane Doe')
-
-      expect(presenter.user).to eq('John Doe')
+    it 'raise an error if the presentee already respond to method' do
+      expect { presenter_class.new(project, user: 'Jane Doe') }.
+        to raise_error Gitlab::View::Presenter::CannotOverrideMethodError
     end
   end