🐛 prefer CRDs when discovery API types, as CRDs contain more betterer information

internal/discovery/client.go

@@ -19,12 +19,15 @@ package discovery
 import (
 	"context"
 	"fmt"
+	"slices"
 	"strings"
 
 	"github.com/kcp-dev/kcp/pkg/crdpuller"
 
 	"k8s.io/apiextensions-apiserver/pkg/apihelpers"
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+	apiextensionsv1client "k8s.io/apiextensions-apiserver/pkg/client/clientset/clientset/typed/apiextensions/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime/schema"
 	utilerrors "k8s.io/apimachinery/pkg/util/errors"
@@ -33,10 +36,12 @@ import (
 	"k8s.io/client-go/discovery"
 	"k8s.io/client-go/rest"
 	"k8s.io/kube-openapi/pkg/util/proto"
+	"k8s.io/utils/ptr"
 )
 
 type Client struct {
 	discoveryClient discovery.DiscoveryInterface
+	crdClient       apiextensionsv1client.ApiextensionsV1Interface
 }
 
 func NewClient(config *rest.Config) (*Client, error) {
@@ -45,40 +50,24 @@ func NewClient(config *rest.Config) (*Client, error) {
 		return nil, err
 	}
 
+	crdClient, err := apiextensionsv1client.NewForConfig(config)
+	if err != nil {
+		return nil, err
+	}
+
 	return &Client{
 		discoveryClient: discoveryClient,
+		crdClient:       crdClient,
 	}, nil
 }
 
 func (c *Client) RetrieveCRD(ctx context.Context, gvk schema.GroupVersionKind) (*apiextensionsv1.CustomResourceDefinition, error) {
-	openapiSchema, err := c.discoveryClient.OpenAPISchema()
-	if err != nil {
-		return nil, err
-	}
-
 	// Most of this code follows the logic in kcp's crd-puller, but is slimmed down
-	// to a) only support openapi and b) extract a specific version, not necessarily
-	// the preferred version.
+	// to extract a specific version, not necessarily the preferred version.
 
-	models, err := proto.NewOpenAPIData(openapiSchema)
-	if err != nil {
-		return nil, err
-	}
-	modelsByGKV, err := openapi.GetModelsByGKV(models)
-	if err != nil {
-		return nil, err
-	}
-
-	protoSchema := modelsByGKV[gvk]
-	if protoSchema == nil {
-		return nil, fmt.Errorf("no models for %v", gvk)
-	}
-
-	var schemaProps apiextensionsv1.JSONSchemaProps
-	errs := crdpuller.Convert(protoSchema, &schemaProps)
-	if len(errs) > 0 {
-		return nil, utilerrors.NewAggregate(errs)
-	}
+	////////////////////////////////////
+	// Resolve GVK into GVR, because we need the resource name to construct
+	// the full CRD name.
 
 	_, resourceLists, err := c.discoveryClient.ServerGroupsAndResources()
 	if err != nil {
@@ -103,6 +92,96 @@ func (c *Client) RetrieveCRD(ctx context.Context, gvk schema.GroupVersionKind) (
 		return nil, fmt.Errorf("could not find %v in APIs", gvk)
 	}
 
+	////////////////////////////////////
+	// If possible, retrieve the GVK as its original CRD, which is always preferred
+	// because it's much more precise than what we can retrieve from the OpenAPI.
+	// If no CRD can be found, fallback to the OpenAPI schema.
+
+	crdName := resource.Name
+	if gvk.Group == "" {
+		crdName += ".core"
+	} else {
+		crdName += "." + gvk.Group
+	}
+
+	crd, err := c.crdClient.CustomResourceDefinitions().Get(ctx, crdName, metav1.GetOptions{})
+
+	// Hooray, we found a CRD! There is so much goodness on a real CRD that instead
+	// of re-creating it later on based on the openapi schema, we take the original
+	// CRD and just strip it down to what we need.
+	if err == nil {
+		// remove all but the requested version
+		crd.Spec.Versions = slices.DeleteFunc(crd.Spec.Versions, func(ver apiextensionsv1.CustomResourceDefinitionVersion) bool {
+			return ver.Name != gvk.Version
+		})
+
+		if len(crd.Spec.Versions) == 0 {
+			return nil, fmt.Errorf("CRD %s does not contain version %s", crdName, gvk.Version)
+		}
+
+		crd.Spec.Versions[0].Served = true
+		crd.Spec.Versions[0].Storage = true
+
+		if apihelpers.IsCRDConditionTrue(crd, apiextensionsv1.NonStructuralSchema) {
+			crd.Spec.Versions[0].Schema = &apiextensionsv1.CustomResourceValidation{
+				OpenAPIV3Schema: &apiextensionsv1.JSONSchemaProps{
+					Type:                   "object",
+					XPreserveUnknownFields: ptr.To(true),
+				},
+			}
+		}
+
+		crd.APIVersion = apiextensionsv1.SchemeGroupVersion.Identifier()
+		crd.Kind = "CustomResourceDefinition"
+
+		// cleanup object meta
+		oldMeta := crd.ObjectMeta
+		crd.ObjectMeta = metav1.ObjectMeta{
+			Name:        oldMeta.Name,
+			Annotations: filterAnnotations(oldMeta.Annotations),
+		}
+
+		// There is only ever one version, so conversion rules do not make sense
+		// (and even if they did, the conversion webhook from the service cluster
+		// would not be available in kcp anyway).
+		crd.Spec.Conversion = &apiextensionsv1.CustomResourceConversion{
+			Strategy: apiextensionsv1.NoneConverter,
+		}
+
+		return crd, nil
+	}
+
+	// any non-404 error is permanent
+	if !apierrors.IsNotFound(err) {
+		return nil, err
+	}
+
+	// CRD not found, so fall back to using the OpenAPI schema
+	openapiSchema, err := c.discoveryClient.OpenAPISchema()
+	if err != nil {
+		return nil, err
+	}
+
+	models, err := proto.NewOpenAPIData(openapiSchema)
+	if err != nil {
+		return nil, err
+	}
+	modelsByGKV, err := openapi.GetModelsByGKV(models)
+	if err != nil {
+		return nil, err
+	}
+
+	protoSchema := modelsByGKV[gvk]
+	if protoSchema == nil {
+		return nil, fmt.Errorf("no models for %v", gvk)
+	}
+
+	var schemaProps apiextensionsv1.JSONSchemaProps
+	errs := crdpuller.Convert(protoSchema, &schemaProps)
+	if len(errs) > 0 {
+		return nil, utilerrors.NewAggregate(errs)
+	}
+
 	hasSubResource := func(subResource string) bool {
 		return allResourceNames.Has(resource.Name + "/" + subResource)
 	}
@@ -125,13 +204,13 @@ func (c *Client) RetrieveCRD(ctx context.Context, gvk schema.GroupVersionKind) (
 		scope = apiextensionsv1.NamespaceScoped
 	}
 
-	crd := &apiextensionsv1.CustomResourceDefinition{
+	out := &apiextensionsv1.CustomResourceDefinition{
 		TypeMeta: metav1.TypeMeta{
 			Kind:       "CustomResourceDefinition",
-			APIVersion: "apiextensions.k8s.io/v1",
+			APIVersion: apiextensionsv1.SchemeGroupVersion.Identifier(),
 		},
 		ObjectMeta: metav1.ObjectMeta{
-			Name: fmt.Sprintf("%s.%s", resource.Name, gvk.Group),
+			Name: crdName,
 		},
 		Spec: apiextensionsv1.CustomResourceDefinitionSpec{
 			Group: gvk.Group,
@@ -160,13 +239,28 @@ func (c *Client) RetrieveCRD(ctx context.Context, gvk schema.GroupVersionKind) (
 		},
 	}
 
-	apiextensionsv1.SetDefaults_CustomResourceDefinition(crd)
+	apiextensionsv1.SetDefaults_CustomResourceDefinition(out)
 
 	if apihelpers.IsProtectedCommunityGroup(gvk.Group) {
-		crd.Annotations = map[string]string{
+		out.Annotations = map[string]string{
 			apiextensionsv1.KubeAPIApprovedAnnotation: "https://github.com/kcp-dev/kubernetes/pull/4",
 		}
 	}
 
-	return crd, nil
+	return out, nil
+}
+
+func filterAnnotations(ann map[string]string) map[string]string {
+	allowlist := []string{
+		apiextensionsv1.KubeAPIApprovedAnnotation,
+	}
+
+	out := map[string]string{}
+	for k, v := range ann {
+		if slices.Contains(allowlist, k) {
+			out[k] = v
+		}
+	}
+
+	return out
 }