From 8c1e8355f8efb322ad6e53229f0cbb14999a8fc2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Wojciech=20Tyczy=C5=84ski?= <wojtekt@google.com>
Date: Fri, 14 Jan 2022 10:14:17 +0100
Subject: [PATCH] Ensure non-nil items in lists

---
 .../apiserver/pkg/endpoints/handlers/patch.go |  6 ---
 .../pkg/endpoints/handlers/response.go        |  2 +-
 .../apiserver/pkg/endpoints/handlers/rest.go  | 43 ++-----------------
 3 files changed, 5 insertions(+), 46 deletions(-)

diff --git a/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/patch.go b/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/patch.go
index d407dcd5039..17919e4aa17 100644
--- a/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/patch.go
+++ b/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/patch.go
@@ -236,12 +236,6 @@ func PatchResource(r rest.Patcher, scope *RequestScope, admit admission.Interfac
 		}
 		trace.Step("Object stored in database")
 
-		if err := setObjectSelfLink(ctx, result, req, scope.Namer); err != nil {
-			scope.err(err, w, req)
-			return
-		}
-		trace.Step("Self-link added")
-
 		status := http.StatusOK
 		if wasCreated {
 			status = http.StatusCreated
diff --git a/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/response.go b/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/response.go
index e19cafdda11..52f083f672f 100644
--- a/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/response.go
+++ b/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/response.go
@@ -59,7 +59,7 @@ func doTransformObject(ctx context.Context, obj runtime.Object, opts interface{}
 	if _, ok := obj.(*metav1.Status); ok {
 		return obj, nil
 	}
-	if err := setObjectSelfLink(ctx, obj, req, scope.Namer); err != nil {
+	if err := ensureNonNilItems(obj); err != nil {
 		return nil, err
 	}
 
diff --git a/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/rest.go b/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/rest.go
index aba9a3f882a..b40423dac34 100644
--- a/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/rest.go
+++ b/staging/src/k8s.io/apiserver/pkg/endpoints/handlers/rest.go
@@ -356,49 +356,14 @@ func dedupOwnerReferencesAndAddWarning(obj runtime.Object, requestContext contex
 	}
 }
 
-// setObjectSelfLink sets the self link of an object as needed.
-// TODO: remove the need for the namer LinkSetters by requiring objects implement either Object or List
-//   interfaces
-func setObjectSelfLink(ctx context.Context, obj runtime.Object, req *http.Request, namer ScopeNamer) error {
-	if utilfeature.DefaultFeatureGate.Enabled(features.RemoveSelfLink) {
-		// Ensure that for empty lists we don't return <nil> items.
-		if meta.IsListType(obj) && meta.LenList(obj) == 0 {
-			if err := meta.SetList(obj, []runtime.Object{}); err != nil {
-				return err
-			}
-		}
-		return nil
-	}
-
-	// We only generate list links on objects that implement ListInterface - historically we duck typed this
-	// check via reflection, but as we move away from reflection we require that you not only carry Items but
-	// ListMeta into order to be identified as a list.
-	if !meta.IsListType(obj) {
-		_, ok := request.RequestInfoFrom(ctx)
-		if !ok {
-			return fmt.Errorf("missing requestInfo")
-		}
-		return nil
-	}
-
-	_, ok := request.RequestInfoFrom(ctx)
-	if !ok {
-		return fmt.Errorf("missing requestInfo")
-	}
-
-	count := 0
-	err := meta.EachListItem(obj, func(obj runtime.Object) error {
-		count++
-		return nil
-	})
-
-	if count == 0 {
+// ensureNonNilItems ensures that for empty lists we don't return <nil> items.
+func ensureNonNilItems(obj runtime.Object) error {
+	if meta.IsListType(obj) && meta.LenList(obj) == 0 {
 		if err := meta.SetList(obj, []runtime.Object{}); err != nil {
 			return err
 		}
 	}
-
-	return err
+	return nil
 }
 
 func summarizeData(data []byte, maxLength int) string {