Fix milestones disappearing when changed on MR

app/assets/javascripts/milestone_select.js

@@ -16,10 +16,10 @@ export default class MilestoneSelect {
         typeof currentProject === 'string' ? JSON.parse(currentProject) : currentProject;
     }
 
-    this.init(els, options);
+    MilestoneSelect.init(els, options);
   }
 
-  init(els, options) {
+  static init(els, options) {
     let $els = $(els);
 
     if (!els) {
@@ -224,7 +224,6 @@ export default class MilestoneSelect {
                 $selectBox.hide();
                 $value.css('display', '');
                 if (data.milestone != null) {
-                  data.milestone.full_path = this.currentProject.full_path;
                   data.milestone.remaining = timeFor(data.milestone.due_date);
                   data.milestone.name = data.milestone.title;
                   $value.html(milestoneLinkTemplate(data.milestone));

app/controllers/projects/merge_requests_controller.rb

@@ -115,7 +115,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
       end
 
       format.json do
-        render json: @merge_request.to_json(include: { milestone: {}, assignee: { only: [:name, :username], methods: [:avatar_url] }, labels: { methods: :text_color } }, methods: [:task_status, :task_status_short])
+        render json: serializer.represent(@merge_request, serializer: 'basic')
       end
     end
   rescue ActiveRecord::StaleObjectError

app/serializers/merge_request_basic_entity.rb

@@ -5,4 +5,8 @@ class MergeRequestBasicEntity < IssuableSidebarEntity
   expose :state
   expose :source_branch_exists?, as: :source_branch_exists
   expose :rebase_in_progress?, as: :rebase_in_progress
+  expose :milestone, using: API::Entities::Milestone
+  expose :labels, using: LabelEntity
+  expose :assignee, using: API::Entities::UserBasic
+  expose :task_status, :task_status_short
 end

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -234,7 +234,7 @@ describe Projects::MergeRequestsController do
         body = JSON.parse(response.body)
 
         expect(body['assignee'].keys)
-          .to match_array(%w(name username avatar_url))
+          .to match_array(%w(name username avatar_url id state web_url))
       end
     end
 

spec/fixtures/api/schemas/entities/merge_request_basic.json

@@ -14,7 +14,21 @@
     "subscribed": { "type": ["boolean", "null"] },
     "participants": { "type": "array" },
     "allow_collaboration": { "type": "boolean"},
-    "allow_maintainer_to_push": { "type": "boolean"}
+    "allow_maintainer_to_push": { "type": "boolean"},
+    "assignee": {
+      "oneOf": [
+        { "type": "null" },
+        { "$ref": "user.json" }
+      ]
+    },
+    "milestone": {
+      "type": [ "object", "null" ]
+    },
+    "labels": {
+      "type": [ "array", "null" ]
+    },
+    "task_status": { "type": "string" },
+    "task_status_short": { "type": "string" }
   },
   "additionalProperties": false
 }