Consider namespaces with no plans as eligible for capping as free

- namespaces don't always get a subscription unless asked for.

ee/app/models/ee/namespace.rb

@@ -301,15 +301,18 @@ module EE
         end
     end
 
-    def on_existing_free_subscription?
+    def has_free_or_no_subscription?
       # this is a side-effect free version of checking if a namespace
-      # is on a free plan - see https://gitlab.com/gitlab-org/gitlab/-/merge_requests/80839#note_851566461
-      strong_memoize(:on_existing_free_subscription) do
-        ::Plan
-          .joins(:hosted_subscriptions)
-          .where(name: ::Plan::FREE)
-          .where(gitlab_subscriptions: { namespace_id: id })
-          .exists?
+      # is on a free plan or has no plan - see https://gitlab.com/gitlab-org/gitlab/-/merge_requests/80839#note_851566461
+      strong_memoize(:has_free_or_no_subscription) do
+        subscription = root_ancestor.gitlab_subscription
+
+        # there is a chance that subscriptions do not have a plan https://gitlab.com/gitlab-org/gitlab/-/merge_requests/81432#note_858514873
+        if subscription&.plan_name
+          subscription.plan_name == ::Plan::FREE
+        else
+          true
+        end
       end
     end
 
@@ -472,7 +475,7 @@ module EE
 
     def apply_free_user_cap?
       return false unless ::Gitlab.com?
-      return false unless root_ancestor.on_existing_free_subscription?
+      return false unless has_free_or_no_subscription?
 
       ::Feature.enabled?(:free_user_cap, root_ancestor, default_enabled: :yaml)
     end

ee/spec/models/ee/namespace_spec.rb

@@ -2255,7 +2255,7 @@ RSpec.describe Namespace do
       context 'when no plan exists' do
         let_it_be(:namespace) { create(:group) }
 
-        it { is_expected.to be false }
+        it { is_expected.to be true }
       end
     end
   end
@@ -2282,23 +2282,70 @@ RSpec.describe Namespace do
     end
   end
 
-  describe '#on_existing_free_subscription?', :saas do
+  describe '#has_free_or_no_subscription?', :saas do
     it 'returns true with a free plan' do
       namespace = create(:group_with_plan, plan: :free_plan)
 
-      expect(namespace.on_existing_free_subscription?).to be(true)
+      expect(namespace.has_free_or_no_subscription?).to be(true)
     end
 
     it 'returns false when the plan is not free' do
       namespace = create(:group_with_plan, plan: :ultimate_plan)
 
-      expect(namespace.on_existing_free_subscription?).to be(false)
+      expect(namespace.has_free_or_no_subscription?).to be(false)
+    end
+
+    it 'returns true when there is no plan' do
+      namespace = create(:namespace)
+
+      expect(namespace.has_free_or_no_subscription?).to be(true)
     end
 
-    it 'returns false when there is no plan' do
+    it 'returns true when there is a subscription with no plan' do
       namespace = create(:namespace)
+      create(:gitlab_subscription, hosted_plan: nil, namespace: namespace)
+
+      expect(namespace.has_free_or_no_subscription?).to be(true)
+    end
+
+    context 'when it is a subgroup' do
+      let(:subgroup) { create(:group, parent: namespace) }
+
+      context 'with a free plan' do
+        let(:namespace) { create(:group_with_plan, plan: :free_plan) }
+
+        it 'returns true' do
+          expect(subgroup.has_free_or_no_subscription?).to be(true)
+        end
+      end
+
+      context 'with a plan that is not free' do
+        let(:namespace) { create(:group_with_plan, plan: :ultimate_plan) }
 
-      expect(namespace.on_existing_free_subscription?).to be(false)
+        it 'returns false' do
+          expect(subgroup.has_free_or_no_subscription?).to be(false)
+        end
+      end
+
+      context 'when there is no plan' do
+        let(:namespace) { create(:group) }
+
+        it 'returns true' do
+          expect(subgroup.has_free_or_no_subscription?).to be(true)
+        end
+      end
+
+      context 'when there is a subscription with no plan' do
+        let(:namespace) { create(:group) }
+
+        before do
+          create(:gitlab_subscription, hosted_plan: nil, namespace: namespace)
+        end
+
+        it 'returns true' do
+          expect(subgroup.has_free_or_no_subscription?).to be(true)
+        end
+      end
     end
   end