[installer] Allow composed render funcs to output no object

Author: easyCZ

install/installer/pkg/common/render.go

@@ -31,6 +31,10 @@ func CompositeRenderFunc(f ...RenderFunc) RenderFunc {
 			if err != nil {
 				return nil, err
 			}
+			if len(obj) == 0 {
+				// the RenderFunc chose not to render anything, possibly based on config it received
+				continue
+			}
 			res = append(res, obj...)
 		}
 		return res, nil

install/installer/pkg/common/render_test.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2022 Gitpod GmbH. All rights reserved.
+// Licensed under the MIT License. See License-MIT.txt in the project root for license information.
+
+package common
+
+import (
+	"github.com/gitpod-io/gitpod/installer/pkg/config/v1"
+	"github.com/gitpod-io/gitpod/installer/pkg/config/versions"
+	"github.com/stretchr/testify/require"
+	"k8s.io/apimachinery/pkg/runtime"
+	"testing"
+)
+
+func TestCompositeRenderFunc_NilObjectsNilError(t *testing.T) {
+	f := CompositeRenderFunc(
+		func(cfg *RenderContext) ([]runtime.Object, error) {
+			return nil, nil
+		})
+
+	ctx, err := NewRenderContext(config.Config{}, versions.Manifest{}, "test_namespace")
+	require.NoError(t, err)
+
+	objects, err := f(ctx)
+	require.NoError(t, err)
+	require.Len(t, objects, 0)
+}