Fix creating/updating issues with epic_iid parameter on API

Fix API request timeout when creating/updating issues using API

ee/changelogs/unreleased/issue_222462.yml

+---
+title: Fix creating/updating issues with epic_iid parameter on API
+merge_request: 34641
+author:
+type: fixed

ee/lib/ee/api/helpers/common_helpers.rb

@@ -15,8 +15,13 @@ module EE
             iid = params.delete(:epic_iid)
 
             if iid.present?
-              epic = EpicsFinder.new(current_user, group_id: group.id, iids: [iid]).first
-              not_found!('Epic') unless epic
+              group_id = user_project&.group&.id
+
+              raise_epic_not_found! unless group_id
+
+              epic = EpicsFinder.new(current_user, group_id: group_id).find_by(iid: iid) # rubocop: disable CodeReuse/ActiveRecord
+
+              raise_epic_not_found! unless epic
 
               params[:epic_id] = epic.id
             end
@@ -24,6 +29,10 @@ module EE
 
           super
         end
+
+        def raise_epic_not_found!
+          not_found!('Epic')
+        end
       end
     end
   end

ee/spec/requests/api/issues_spec.rb

@@ -254,11 +254,26 @@ RSpec.describe API::Issues, :mailer do
             group.add_owner(user)
           end
 
-          it 'sets epic on issue' do
-            request
+          context 'with epic_id parameter' do
+            let(:params) { { title: 'issue with epic', epic_id: epic.id } }
+
+            it 'sets epic on issue' do
+              request
+
+              expect(response).to have_gitlab_http_status(:success)
+              expect(json_response['epic_iid']).to eq(epic.iid)
+            end
+          end
+
+          context 'with deprecated epic_iid parameter' do
+            let(:params) { { title: 'issue with epic', epic_iid: epic.iid } }
+
+            it 'sets epic on issue' do
+              request
 
-            expect(response).to have_gitlab_http_status(:success)
-            expect(json_response['epic_iid']).to eq(epic.iid)
+              expect(response).to have_gitlab_http_status(:success)
+              expect(json_response['epic_iid']).to eq(epic.iid)
+            end
           end
         end