ratcheting: disable correlation by index

discussion: https://github.com/kubernetes/kubernetes/pull/121118#discussion_r1358865893

Kubernetes-commit: fb1fc8b4a72758688d1251278579b2b0ac666fc7

pkg/cel/common/equality.go

@@ -114,19 +114,15 @@ func (r *CorrelatedObject) correlateOldValueForChildAtNewIndex(index int) interf
 		// of value
 		// (would allow you to add/remove items from sets with ratcheting but not change them)
 		return nil
+	case "":
+		fallthrough
 	case "atomic":
-		// Atomic lists are not correlatable by item
+		// Atomic lists are the default are not correlatable by item
 		// Ratcheting is not available on a per-index basis
 		return nil
 	default:
-		// Correlate by-index by default.
-		//
-		// Cannot correlate an out-of-bounds index
-		if len(oldAsList) <= index {
-			return nil
-		}
-
-		return oldAsList[index]
+		// Unrecognized list type. Assume non-correlatable.
+		return nil
 	}
 }
 

pkg/cel/common/equality_test.go

@@ -142,16 +142,14 @@ func TestCorrelation(t *testing.T) {
 			OldValue: "b",
 		},
 		{
-			Name:          "Basic Index",
+			Name:          "Atomic Array not correlatable",
 			RootObject:    mustUnstructured(`[a, b]`),
 			RootOldObject: mustUnstructured(`[a, b]`),
 			Schema: mustSchema(`
                 items:
                   type: string
             `),
-			KeyPath:  []interface{}{1},
-			NewValue: "b",
-			OldValue: "b",
+			KeyPath: []interface{}{1},
 		},
 		{
 			Name: "Added Key Not In Old Object",
@@ -187,7 +185,7 @@ func TestCorrelation(t *testing.T) {
 			KeyPath: []interface{}{2},
 		},
 		{
-			Name: "Changed Index In Old Object",
+			Name: "Changed Index In Old Object not correlatable",
 			RootObject: []interface{}{
 				"a",
 				"b",
@@ -200,9 +198,7 @@ func TestCorrelation(t *testing.T) {
                 items:
                     type: string
             `),
-			KeyPath:  []interface{}{1},
-			NewValue: "b",
-			OldValue: "oldB",
+			KeyPath: []interface{}{1},
 		},
 		{
 			Name: "Changed Index In Nested Old Object",