Adjusts Member awaiting scope to be distinct

Users can potentially be awaiting members of multiple groups but the
scope need only return distinct results

Changelog: changed
EE: true

ee/app/models/ee/member.rb

@@ -30,11 +30,13 @@ module EE
         includes(:user, source: [:route, :parent])
       end
 
-      scope :awaiting_or_invited_for_group, -> (group) do
+      scope :distinct_awaiting_or_invited_for_group, -> (group) do
         awaiting
         .or(::Member.invite)
         .in_hierarchy(group)
+        .select('DISTINCT ON (members.user_id, members.invite_email) members.*')
         .includes(:user)
+        .order(:user_id, :invite_email)
       end
     end
 

ee/lib/ee/api/members.rb

@@ -105,7 +105,7 @@ module EE
             bad_request! unless group.root?
             bad_request! unless can?(current_user, :admin_group_member, group)
 
-            members = ::Member.awaiting_or_invited_for_group(group)
+            members = ::Member.distinct_awaiting_or_invited_for_group(group)
 
             present paginate(members), with: ::API::Entities::PendingMember
           end

ee/spec/models/member_spec.rb

@@ -246,7 +246,7 @@ RSpec.describe Member, type: :model do
     end
   end
 
-  describe '.awaiting_or_invited_for_group' do
+  describe '.distinct_awaiting_or_invited_for_group' do
     let_it_be(:active_group_member) { create(:group_member, group: group) }
     let_it_be(:awaiting_group_member) { create(:group_member, :awaiting, group: group) }
     let_it_be(:awaiting_subgroup_member) { create(:group_member, :awaiting, group: sub_group) }
@@ -254,8 +254,11 @@ RSpec.describe Member, type: :model do
     let_it_be(:awaiting_invited_member) { create(:group_member, :awaiting, :invited, group: group) }
     let_it_be(:active_invited_member) { create(:group_member, :invited, group: group) }
 
+    subject(:results) { described_class.distinct_awaiting_or_invited_for_group(group) }
+
     it 'returns the correct members' do
-      expect(described_class.awaiting_or_invited_for_group(group)).to match_array [
+      expect(results.size).to eq 5
+      expect(results).to match_array [
         awaiting_group_member,
         awaiting_subgroup_member,
         awaiting_project_member,
@@ -263,5 +266,21 @@ RSpec.describe Member, type: :model do
         active_invited_member
       ]
     end
+
+    it 'does not return additional results for duplicates' do
+      create(:group_member, :awaiting, group: sub_group, user: awaiting_group_member.user)
+      create(:group_member, :invited, group: sub_group, invite_email: awaiting_invited_member.invite_email)
+
+      expect(results.size).to eq 5
+      expect(results.map(&:user_id).compact).to contain_exactly(
+        awaiting_group_member.user_id,
+        awaiting_subgroup_member.user_id,
+        awaiting_project_member.user_id
+      )
+      expect(results.map(&:invite_email).compact).to contain_exactly(
+        awaiting_invited_member.invite_email,
+        active_invited_member.invite_email
+      )
+    end
   end
 end

ee/spec/requests/api/members_spec.rb

@@ -1148,6 +1148,20 @@ RSpec.describe API::Members do
           ]
         end
 
+        it 'returns only one membership per user' do
+          create(:group_member, :awaiting, group: subgroup, user: pending_group_member.user)
+          create(:group_member, :awaiting, :invited, group: subgroup, invite_email: pending_invited_member.invite_email)
+
+          get api(url, owner)
+
+          expect(json_response.map { |m| m['id'] }).to match_array [
+            pending_group_member.id,
+            pending_subgroup_member.id,
+            pending_project_member.id,
+            pending_invited_member.id
+          ]
+        end
+
         it 'paginates the response' do
           get api(url, owner)