Fix smartcard param check in User::BuildService

changelogs/unreleased/33641-fix_smartcard_param_check_in_user_build.yml

+---
+title: Fix user registration when smartcard authentication is enabled
+merge_request: 26800
+author:
+type: fixed

ee/app/services/ee/users/build_service.rb

@@ -70,7 +70,7 @@ module EE
       def build_smartcard_identity(user, params)
         smartcard_identity_attrs = params.slice(:certificate_subject, :certificate_issuer)
 
-        if smartcard_identity_attrs.any?
+        unless smartcard_identity_attrs.empty?
           user.smartcard_identities.build(subject: params[:certificate_subject],
                                           issuer: params[:certificate_issuer])
         end

ee/spec/services/ee/users/build_service_spec.rb

@@ -28,6 +28,39 @@ describe Users::BuildService do
           end
         end
       end
+
+      context 'smartcard authentication enabled' do
+        before do
+          allow(Gitlab::Auth::Smartcard).to receive(:enabled?).and_return(true)
+        end
+
+        context 'smartcard params' do
+          let(:subject) { '/O=Random Corp Ltd/CN=gitlab-user/emailAddress=gitlab-user@random-corp.org' }
+          let(:issuer) { '/O=Random Corp Ltd/CN=Random Corp' }
+          let(:smartcard_identity_params) do
+            { certificate_subject: subject, certificate_issuer: issuer }
+          end
+
+          before do
+            params.merge!(smartcard_identity_params)
+          end
+
+          it 'sets smartcard identity attributes' do
+            expect(SmartcardIdentity).to(
+              receive(:new)
+                .with(hash_including(issuer: issuer, subject: subject))
+                .and_call_original)
+
+            service.execute
+          end
+        end
+
+        context 'missing smartcard params' do
+          it 'works as expected' do
+            expect { service.execute }.not_to raise_error
+          end
+        end
+      end
     end
   end
 end