Ensure Members::ApproveAccessRequestService can fin a requester by ID

app/controllers/concerns/membership_actions.rb

@@ -9,7 +9,7 @@ module MembershipActions
   end
 
   def approve_access_request
-    Members::ApproveAccessRequestService.new(membershipable, current_user, user_id: params[:id]).execute
+    Members::ApproveAccessRequestService.new(membershipable, current_user, params).execute
 
     redirect_to polymorphic_url([membershipable, :members])
   end

app/services/members/approve_access_request_service.rb

@@ -11,7 +11,8 @@ module Members
     end
 
     def execute
-      access_requester = source.requesters.find_by!(user_id: params[:user_id])
+      condition = params[:user_id] ? { user_id: params[:user_id] } : { id: params[:id] }
+      access_requester = source.requesters.find_by!(condition)
 
       raise Gitlab::Access::AccessDeniedError if cannot_update_access_requester?(access_requester)
 

spec/controllers/groups/group_members_controller_spec.rb

@@ -2,9 +2,10 @@ require 'spec_helper'
 
 describe Groups::GroupMembersController do
   let(:user)  { create(:user) }
-  let(:group) { create(:group) }
 
   describe '#index' do
+    let(:group) { create(:group) }
+
     before do
       group.add_owner(user)
       stub_application_setting(restricted_visibility_levels: [Gitlab::VisibilityLevel::PUBLIC])

spec/services/members/approve_access_request_service_spec.rb

@@ -83,6 +83,14 @@ describe Members::ApproveAccessRequestService, services: true do
       it_behaves_like 'a service approving an access request' do
         let(:source) { group }
       end
+
+      context 'when given a :id' do
+        let(:params) { { id: project.requesters.find_by!(user_id: access_requester.id).id } }
+
+        it_behaves_like 'a service approving an access request' do
+          let(:source) { project }
+        end
+      end
     end
   end
 end