Fix issue with blank keyset pagination parameters

Refers to https://gitlab.com/gitlab-org/gitlab/-/issues/227166

changelogs/unreleased/ab-keyset-blank-parameters.yml

+---
+title: Fix issue with blank keyset pagination parameters
+merge_request: 37351
+author:
+type: fixed

lib/api/helpers.rb

@@ -559,8 +559,8 @@ module API
       finder_params[:search_namespaces] = true if params[:search_namespaces].present?
       finder_params[:user] = params.delete(:user) if params[:user]
       finder_params[:custom_attributes] = params[:custom_attributes] if params[:custom_attributes]
-      finder_params[:id_after] = params[:id_after] if params[:id_after]
-      finder_params[:id_before] = params[:id_before] if params[:id_before]
+      finder_params[:id_after] = sanitize_id_param(params[:id_after]) if params[:id_after]
+      finder_params[:id_before] = sanitize_id_param(params[:id_before]) if params[:id_before]
       finder_params[:last_activity_after] = params[:last_activity_after] if params[:last_activity_after]
       finder_params[:last_activity_before] = params[:last_activity_before] if params[:last_activity_before]
       finder_params[:repository_storage] = params[:repository_storage] if params[:repository_storage]
@@ -659,6 +659,10 @@ module API
     def ip_address
       env["action_dispatch.remote_ip"].to_s || request.ip
     end
+
+    def sanitize_id_param(id)
+      id.present? ? id.to_i : nil
+    end
   end
 end
 

spec/requests/api/projects_spec.rb

@@ -386,6 +386,14 @@ RSpec.describe API::Projects do
           let(:current_user) { user }
           let(:projects) { [public_project, project, project2, project3].select { |p| p.id > project2.id } }
         end
+
+        context 'regression: empty string is ignored' do
+          it_behaves_like 'projects response' do
+            let(:filter) { { id_after: '' } }
+            let(:current_user) { user }
+            let(:projects) { [public_project, project, project2, project3] }
+          end
+        end
       end
 
       context 'and using id_before' do
@@ -394,6 +402,14 @@ RSpec.describe API::Projects do
           let(:current_user) { user }
           let(:projects) { [public_project, project, project2, project3].select { |p| p.id < project2.id } }
         end
+
+        context 'regression: empty string is ignored' do
+          it_behaves_like 'projects response' do
+            let(:filter) { { id_before: '' } }
+            let(:current_user) { user }
+            let(:projects) { [public_project, project, project2, project3] }
+          end
+        end
       end
 
       context 'and using both id_after and id_before' do