Allow knative do be uninstalled:

- After uninstalling the knative helm chart it's necessary to also
remove some leftover resources to allow the cluster to be clean
and knative to be reinstalleable.
- Adds knative uninstall disclaimer
- Uninstall ksvc before uninstalling knative

Make list of Knative and Ingres resources explicit

- To avoid deleting unwanted resources we are listing exact
which resources will be deleted rather than simply deleting any
resource that contains istio or knative words.

3 files changed, 43 insertions, 3 deletions

diff --git a/spec/features/projects/clusters/applications_spec.rb b/spec/features/projects/clusters/applications_spec.rb
index d0182270d82..de97c8a8bc0 100644
--- a/spec/features/projects/clusters/applications_spec.rb
+++ b/spec/features/projects/clusters/applications_spec.rb
@@ -126,7 +126,7 @@ describe 'Clusters Applications', :js do
             it 'shows status transition' do
               page.within('.js-cluster-application-row-knative') do
                 expect(domainname_form_value).to eq('domain.example.org')
-                expect(page).to have_css('.js-cluster-application-install-button', exact_text: 'Installed')
+                expect(page).to have_css('.js-cluster-application-uninstall-button', exact_text: 'Uninstall')
               end
 
               expect(page).to have_content('Knative was successfully installed on your Kubernetes cluster')
diff --git a/spec/models/clusters/applications/cert_manager_spec.rb b/spec/models/clusters/applications/cert_manager_spec.rb
index 8d853a04e33..6e1f80cadc2 100644
--- a/spec/models/clusters/applications/cert_manager_spec.rb
+++ b/spec/models/clusters/applications/cert_manager_spec.rb
@@ -48,7 +48,7 @@ describe Clusters::Applications::CertManager do
       expect(subject.version).to eq('v0.5.2')
       expect(subject).to be_rbac
       expect(subject.files).to eq(cert_manager.files.merge(cluster_issuer_file))
-      expect(subject.postinstall).to eq(['/usr/bin/kubectl create -f /data/helm/certmanager/config/cluster_issuer.yaml'])
+      expect(subject.postinstall).to eq(['kubectl create -f /data/helm/certmanager/config/cluster_issuer.yaml'])
     end
 
     context 'for a specific user' do
diff --git a/spec/models/clusters/applications/knative_spec.rb b/spec/models/clusters/applications/knative_spec.rb
index 7f4819cbb9a..342ed907854 100644
--- a/spec/models/clusters/applications/knative_spec.rb
+++ b/spec/models/clusters/applications/knative_spec.rb
@@ -39,7 +39,7 @@ describe Clusters::Applications::Knative do
   describe '#can_uninstall?' do
     subject { knative.can_uninstall? }
 
-    it { is_expected.to be_falsey }
+    it { is_expected.to be_truthy }
   end
 
   describe '#schedule_status_update with external_ip' do
@@ -129,6 +129,46 @@ describe Clusters::Applications::Knative do
     it_behaves_like 'a command'
   end
 
+  describe '#uninstall_command' do
+    subject { knative.uninstall_command }
+
+    it { is_expected.to be_an_instance_of(Gitlab::Kubernetes::Helm::DeleteCommand) }
+
+    it "removes knative deployed services before uninstallation" do
+      2.times do |i|
+        cluster_project = create(:cluster_project, cluster: knative.cluster)
+
+        create(:cluster_kubernetes_namespace,
+          cluster: cluster_project.cluster,
+          cluster_project: cluster_project,
+          project: cluster_project.project,
+          namespace: "namespace_#{i}")
+      end
+
+      remove_namespaced_services_script = [
+        "kubectl delete ksvc --all -n #{knative.cluster.kubernetes_namespaces.first.namespace}",
+        "kubectl delete ksvc --all -n #{knative.cluster.kubernetes_namespaces.second.namespace}"
+      ]
+
+      expect(subject.predelete).to match_array(remove_namespaced_services_script)
+    end
+
+    it "initializes command with all necessary postdelete script" do
+      api_resources = YAML.safe_load(File.read(Rails.root.join(Clusters::Applications::Knative::API_RESOURCES_PATH)))
+
+      remove_knative_istio_leftovers_script = [
+        "kubectl delete --ignore-not-found ns knative-serving",
+        "kubectl delete --ignore-not-found ns knative-build"
+      ]
+
+      full_delete_commands_size = api_resources.size + remove_knative_istio_leftovers_script.size
+
+      expect(subject.postdelete).to include(*remove_knative_istio_leftovers_script)
+      expect(subject.postdelete.size).to eq(full_delete_commands_size)
+      expect(subject.postdelete[2]).to eq("kubectl delete --ignore-not-found crd #{api_resources[0]}")
+    end
+  end
+
   describe '#files' do
     let(:application) { knative }
     let(:values) { subject[:'values.yaml'] }