Refactor code climate artifact code on backend

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/merge_request.rb

@@ -34,6 +34,9 @@ class MergeRequest < ActiveRecord::Base
   delegate :commits, :real_size, :commits_sha, :commits_count,
     to: :merge_request_diff, prefix: nil
 
+  delegate :codeclimate_artifact, to: :head_pipeline, prefix: :head, allow_nil: true
+  delegate :codeclimate_artifact, to: :base_pipeline, prefix: :base, allow_nil: true
+
   # When this attribute is true some MR validation is ignored
   # It allows us to close or modify broken merge requests
   attr_accessor :allow_broken
@@ -996,16 +999,8 @@ class MergeRequest < ActiveRecord::Base
     @base_pipeline ||= project.pipelines.find_by(sha: merge_request_diff&.base_commit_sha)
   end
 
-  def codeclimate_artifact
-    @codeclimate_artifact ||= head_pipeline&.codeclimate_artifact
-  end
-
-  def base_codeclimate_artifact
-    @base_codeclimate_artifact ||= base_pipeline&.codeclimate_artifact
-  end
-
   def has_codeclimate_data?
-    codeclimate_artifact&.success? &&
+    head_codeclimate_artifact&.success? &&
       base_codeclimate_artifact&.success?
   end
 end

app/serializers/merge_request_entity.rb

@@ -197,17 +197,17 @@ class MergeRequestEntity < IssuableEntity
   end
 
   # EE-specific
-  expose :codeclimate, if: lambda { |mr, _| mr.has_codeclimate_data? && can?(current_user, :read_build, mr.project) } do
-    expose :head_path do |merge_request|
-      raw_namespace_project_build_artifacts_url(merge_request.project.namespace,
-                                                merge_request.project,
-                                                merge_request.codeclimate_artifact,
+  expose :codeclimate, if: -> (mr, _) { mr.has_codeclimate_data? } do
+    expose :head_path, if: -> (mr, _) { can?(current_user, :read_build, mr.head_codeclimate_artifact) } do |merge_request|
+      raw_namespace_project_build_artifacts_url(merge_request.source_project.namespace,
+                                                merge_request.source_project,
+                                                merge_request.head_codeclimate_artifact,
                                                 path: 'codeclimate.json')
     end
 
-    expose :base_path do |merge_request|
-      raw_namespace_project_build_artifacts_url(merge_request.project.namespace,
-                                                merge_request.project,
+    expose :base_path, if: -> (mr, _) { can?(current_user, :read_build, mr.base_codeclimate_artifact) } do |merge_request|
+      raw_namespace_project_build_artifacts_url(merge_request.target_project.namespace,
+                                                merge_request.target_project,
                                                 merge_request.base_codeclimate_artifact,
                                                 path: 'codeclimate.json')
     end