[Multiple issue assignees] fix v4 API for issues

app/controllers/concerns/issuable_collections.rb

@@ -40,7 +40,7 @@ module IssuableCollections
   end
 
   def issues_collection
-    issues_finder.execute.preload(:project, :author, :labels, :milestone, :assignees, project: :namespace)
+    issues_finder.execute.preload(:project, :author, :assignees, :labels, :milestone, project: :namespace)
   end
 
   def merge_requests_collection

lib/api/issues.rb

@@ -31,7 +31,7 @@ module API
 
       params :issue_params do
         optional :description, type: String, desc: 'The description of an issue'
-        optional :assignee_id, type: Integer, desc: 'The ID of a user to assign issue'
+        optional :assignee_ids, type: Array[Integer], desc: 'The ID of a user to assign issue'
         optional :milestone_id, type: Integer, desc: 'The ID of a milestone to assign issue'
         optional :labels, type: String, desc: 'Comma-separated list of label names'
         optional :due_date, type: String, desc: 'Date string in the format YEAR-MONTH-DAY'
@@ -156,7 +156,7 @@ module API
                               desc: 'Date time when the issue was updated. Available only for admins and project owners.'
         optional :state_event, type: String, values: %w[reopen close], desc: 'State of the issue'
         use :issue_params
-        at_least_one_of :title, :description, :assignee_id, :milestone_id,
+        at_least_one_of :title, :description, :assignee_ids, :milestone_id,
                         :labels, :created_at, :due_date, :confidential, :state_event,
                         :weight
       end

spec/fixtures/api/schemas/public_api/v4/issues.json

@@ -33,7 +33,9 @@
         },
         "additionalProperties": false
       },
-      "assignee": {
+      "assignees": {
+        "type": "array",
+        "items": {
           "type": ["object", "null"],
           "properties": {
             "name": { "type": "string" },
@@ -44,6 +46,7 @@
             "web_url": { "type": "uri" }
           },
           "additionalProperties": false
+        }
       },
       "author": {
         "type": "object",
@@ -68,7 +71,7 @@
     "required": [
       "id", "iid", "project_id", "title", "description",
       "state", "created_at", "updated_at", "labels",
-      "milestone", "assignee", "author", "user_notes_count",
+      "milestone", "assignees", "author", "user_notes_count",
       "upvotes", "downvotes", "due_date", "confidential",
       "web_url", "weight"
     ],

spec/requests/api/issues_spec.rb

@@ -788,7 +788,7 @@ describe API::Issues, api: true  do
       expect(json_response['updated_at']).to be_present
       expect(json_response['labels']).to eq(issue.label_names)
       expect(json_response['milestone']).to be_a Hash
-      expect(json_response['assignee']).to be_a Hash
+      expect(json_response['assignees']).to be_a Array
       expect(json_response['author']).to be_a Hash
       expect(json_response['confidential']).to be_falsy
       expect(json_response['weight']).to be_nil