Designs: return an error if uploading designs with duplicate names

app/services/design_management/save_designs_service.rb

@@ -16,6 +16,7 @@ module DesignManagement
     def execute
       return error("Not allowed!") unless can_create_designs?
       return error("Only #{MAX_FILES} files are allowed simultaneously") if files.size > MAX_FILES
+      return error("Duplicate filenames are not allowed!") if files.map(&:original_filename).uniq.length != files.length
 
       uploaded_designs, version = upload_designs!
       skipped_designs = designs - uploaded_designs

changelogs/unreleased/khanchi-designs-patch.yml

+---
+title: 'Designs: return an error if uploading designs with duplicate names'
+merge_request: 42514
+author: Sushil Khanchi
+type: fixed

spec/services/design_management/save_designs_service_spec.rb

@@ -271,6 +271,14 @@ RSpec.describe DesignManagement::SaveDesignsService do
             expect(response[:message]).to match(/only \d+ files are allowed simultaneously/i)
           end
         end
+
+        context 'when uploading duplicate files' do
+          let(:files) { [rails_sample, dk_png, rails_sample] }
+
+          it 'returns the correct error' do
+            expect(response[:message]).to match('Duplicate filenames are not allowed!')
+          end
+        end
       end
 
       context 'when the user is not allowed to upload designs' do