Nullify platform Kubernetes namespace if blank

app/models/clusters/platforms/kubernetes.rb

@@ -23,11 +23,12 @@ module Clusters
         key: Settings.attr_encrypted_db_key_base_truncated,
         algorithm: 'aes-256-cbc'
 
+      before_validation :nullify_blank_namespace
       before_validation :enforce_namespace_to_lower_case
       before_validation :enforce_ca_whitespace_trimming
 
       validates :namespace,
-        allow_blank: true,
+        allow_nil: true,
         length: 1..63,
         format: {
           with: Gitlab::Regex.kubernetes_namespace_regex,
@@ -190,6 +191,10 @@ module Clusters
 
         true
       end
+
+      def nullify_blank_namespace
+        self.namespace = nil if namespace.blank?
+      end
     end
   end
 end

changelogs/unreleased/31728-nullify-cluster-namespace-if-blank.yml

+---
+title: Nullify platform Kubernetes namespace if blank
+merge_request: 17657
+author:
+type: fixed

spec/models/clusters/platforms/kubernetes_spec.rb

@@ -19,14 +19,23 @@ describe Clusters::Platforms::Kubernetes do
   it_behaves_like 'having unique enum values'
 
   describe 'before_validation' do
+    let(:kubernetes) { create(:cluster_platform_kubernetes, :configured, namespace: namespace) }
+
     context 'when namespace includes upper case' do
-      let(:kubernetes) { create(:cluster_platform_kubernetes, :configured, namespace: namespace) }
       let(:namespace) { 'ABC' }
 
       it 'converts to lower case' do
         expect(kubernetes.namespace).to eq('abc')
       end
     end
+
+    context 'when namespace is blank' do
+      let(:namespace) { '' }
+
+      it 'nullifies the namespace' do
+        expect(kubernetes.namespace).to be_nil
+      end
+    end
   end
 
   describe 'validation' do
@@ -35,8 +44,8 @@ describe Clusters::Platforms::Kubernetes do
     context 'when validates namespace' do
       let(:kubernetes) { build(:cluster_platform_kubernetes, :configured, namespace: namespace) }
 
-      context 'when namespace is blank' do
-        let(:namespace) { '' }
+      context 'when namespace is nil' do
+        let(:namespace) { nil }
 
         it { is_expected.to be_truthy }
       end