feat: add a package to convert unstructured into typed (#8484)

Signed-off-by: Charles-Edouard Brétéché <charles.edouard@nirmata.com>

cmd/cli/kubectl-kyverno/_testdata/resources/namespace.yaml

@@ -0,0 +1,6 @@
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: prod-bus-app1
+  labels:
+    purpose: production

cmd/cli/kubectl-kyverno/resource/convert/convert.go

@@ -0,0 +1,18 @@
+package convert
+
+import (
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+func Into[T any](untyped unstructured.Unstructured, result *T) error {
+	return runtime.DefaultUnstructuredConverter.FromUnstructuredWithValidation(untyped.UnstructuredContent(), result, true)
+}
+
+func To[T any](untyped unstructured.Unstructured) (*T, error) {
+	var result T
+	if err := Into(untyped, &result); err != nil {
+		return nil, err
+	}
+	return &result, nil
+}

cmd/cli/kubectl-kyverno/resource/convert/convert_test.go

@@ -0,0 +1,42 @@
+package convert
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"sigs.k8s.io/yaml"
+)
+
+func TestTo(t *testing.T) {
+	{
+		data, err := os.ReadFile("../../_testdata/policies/check-image.yaml")
+		require.NoError(t, err)
+
+		json, err := yaml.YAMLToJSON(data)
+		require.NoError(t, err)
+
+		var untyped unstructured.Unstructured
+		require.NoError(t, untyped.UnmarshalJSON(json))
+
+		typed, err := To[corev1.ConfigMap](untyped)
+		require.Nil(t, typed)
+		require.Error(t, err)
+	}
+	{
+		data, err := os.ReadFile("../../_testdata/resources/namespace.yaml")
+		require.NoError(t, err)
+
+		json, err := yaml.YAMLToJSON(data)
+		require.NoError(t, err)
+
+		var untyped unstructured.Unstructured
+		require.NoError(t, untyped.UnmarshalJSON(json))
+
+		typed, err := To[corev1.Namespace](untyped)
+		require.NotNil(t, typed)
+		require.NoError(t, err)
+	}
+}