PUT MergeRequest API endpoint - accept labels as an array

lib/api/merge_requests.rb

@@ -179,8 +179,8 @@ module API
           optional :description, type: String, desc: 'The description of the merge request'
           optional :assignee_id, type: Integer, desc: 'The ID of a user to assign the merge request'
           optional :milestone_id, type: Integer, desc: 'The ID of a milestone to assign the merge request'
-          optional :labels, type: String, desc: 'Comma-separated list of label names'
-          optional :remove_source_branch, type: Boolean, desc: 'Delete source branch when merging'
+          optional :labels, type: String, coerce_with: ->(val) { val.is_a?(Array) ? val.join(', ') : val }, desc: 'Comma-separated list of label names'
+          optional :remove_source_branch, type: Boolean, desc: 'Remove source branch when merging'
           optional :allow_collaboration, type: Boolean, desc: 'Allow commits from members who can merge to the target branch'
           optional :allow_maintainer_to_push, type: Boolean, as: :allow_collaboration, desc: '[deprecated] See allow_collaboration'
           optional :squash, type: Grape::API::Boolean, desc: 'When true, the commits will be squashed into a single commit on merge'

spec/requests/api/merge_requests_spec.rb

@@ -1137,6 +1137,19 @@ describe API::MergeRequests do
       expect(json_response['labels']).to include '&'
     end
 
+    it 'also accepts labels as an array' do
+      put api("/projects/#{project.id}/merge_requests/#{merge_request.iid}", user),
+        title: 'new issue',
+        labels: ['label', 'label?', 'label&foo', '?', '&']
+
+      expect(response.status).to eq(200)
+      expect(json_response['labels']).to include 'label'
+      expect(json_response['labels']).to include 'label?'
+      expect(json_response['labels']).to include 'label&foo'
+      expect(json_response['labels']).to include '?'
+      expect(json_response['labels']).to include '&'
+    end
+
     it 'does not update state when title is empty' do
       put api("/projects/#{project.id}/merge_requests/#{merge_request.iid}", user), params: { state_event: 'close', title: nil }