5 files changed, 42 insertions, 7 deletions
diff --git a/app/serializers/issuable_sidebar_entity.rb b/app/serializers/issuable_sidebar_entity.rb
new file mode 100644
index 00000000000..ff23d8bf0c7
--- /dev/null
+++ b/app/serializers/issuable_sidebar_entity.rb
@@ -0,0 +1,16 @@
+class IssuableSidebarEntity < Grape::Entity
+  include RequestAwareEntity
+
+  expose :participants, using: ::API::Entities::UserBasic do |issuable|
+    issuable.participants(request.current_user)
+  end
+
+  expose :subscribed do |issuable|
+    issuable.subscribed?(request.current_user, issuable.project)
+  end
+
+  expose :time_estimate
+  expose :total_time_spent
+  expose :human_time_estimate
+  expose :human_total_time_spent
+end
diff --git a/app/serializers/issue_serializer.rb b/app/serializers/issue_serializer.rb
index 4fff54a9126..2555595379b 100644
--- a/app/serializers/issue_serializer.rb
+++ b/app/serializers/issue_serializer.rb
@@ -1,3 +1,16 @@
 class IssueSerializer < BaseSerializer
-  entity IssueEntity
+  # This overrided method takes care of which entity should be used
+  # to serialize the `issue` based on `basic` key in `opts` param.
+  # Hence, `entity` doesn't need to be declared on the class scope.
+  def represent(merge_request, opts = {})
+    entity =
+      case opts[:serializer]
+      when 'sidebar'
+        IssueSidebarEntity
+      else
+        IssueEntity
+      end
+
+    super(merge_request, opts, entity)
+  end
 end
diff --git a/app/serializers/issue_sidebar_entity.rb b/app/serializers/issue_sidebar_entity.rb
new file mode 100644
index 00000000000..6c823dbfe95
--- /dev/null
+++ b/app/serializers/issue_sidebar_entity.rb
@@ -0,0 +1,3 @@
+class IssueSidebarEntity < IssuableSidebarEntity
+  expose :assignees, using: API::Entities::UserBasic
+end
diff --git a/app/serializers/merge_request_basic_entity.rb b/app/serializers/merge_request_basic_entity.rb
index 8461f158bb5..d54a6516aed 100644
--- a/app/serializers/merge_request_basic_entity.rb
+++ b/app/serializers/merge_request_basic_entity.rb
@@ -1,11 +1,7 @@
-class MergeRequestBasicEntity < Grape::Entity
+class MergeRequestBasicEntity < IssuableSidebarEntity
   expose :assignee_id
   expose :merge_status
   expose :merge_error
   expose :state
   expose :source_branch_exists?, as: :source_branch_exists
-  expose :time_estimate
-  expose :total_time_spent
-  expose :human_time_estimate
-  expose :human_total_time_spent
 end
diff --git a/app/serializers/merge_request_serializer.rb b/app/serializers/merge_request_serializer.rb
index f67034ce47a..e9d98d8baca 100644
--- a/app/serializers/merge_request_serializer.rb
+++ b/app/serializers/merge_request_serializer.rb
@@ -3,7 +3,14 @@ class MergeRequestSerializer < BaseSerializer
   # to serialize the `merge_request` based on `basic` key in `opts` param.
   # Hence, `entity` doesn't need to be declared on the class scope.
   def represent(merge_request, opts = {})
-    entity = opts[:basic] ? MergeRequestBasicEntity : MergeRequestEntity
+    entity =
+      case opts[:serializer]
+      when 'basic', 'sidebar'
+        MergeRequestBasicEntity
+      else
+        MergeRequestEntity
+      end
+
     super(merge_request, opts, entity)
   end
 end