Fix bug where attempting to use patch with deleteFromPrimitiveList on an empty or nonexistent list incorrectly adds the item to be removed.

staging/src/k8s.io/apimachinery/pkg/util/strategicpatch/patch.go

@@ -1328,15 +1328,19 @@ func mergeMap(original, patch map[string]interface{}, schema LookupPatchMeta, me
 
 		_, ok := original[k]
 		if !ok {
+			if !isDeleteList {
 				// If it's not in the original document, just take the patch value.
 				original[k] = patchV
+			}
 			continue
 		}
 
 		originalType := reflect.TypeOf(original[k])
 		patchType := reflect.TypeOf(patchV)
 		if originalType != patchType {
+			if !isDeleteList {
 				original[k] = patchV
+			}
 			continue
 		}
 		// If they're both maps or lists, recurse into the value.

staging/src/k8s.io/apimachinery/pkg/util/strategicpatch/patch_test.go

@@ -669,6 +669,57 @@ mergingList:
 			ExpectedError: "does not contain declared merge key",
 		},
 	},
+	{
+		Description: "$deleteFromPrimitiveList of nonexistent item in primitive list should not add the item to the list",
+		StrategicMergePatchRawTestCaseData: StrategicMergePatchRawTestCaseData{
+			Original: []byte(`
+mergingIntList:
+  - 1
+  - 2
+`),
+			TwoWay: []byte(`
+$deleteFromPrimitiveList/mergingIntList:
+  - 3
+`),
+			Modified: []byte(`
+mergingIntList:
+  - 1
+  - 2
+`),
+		},
+	},
+	{
+		Description: "$deleteFromPrimitiveList on empty primitive list should not add the item to the list",
+		StrategicMergePatchRawTestCaseData: StrategicMergePatchRawTestCaseData{
+			Original: []byte(`
+mergingIntList:
+`),
+			TwoWay: []byte(`
+$deleteFromPrimitiveList/mergingIntList:
+  - 3
+`),
+			Modified: []byte(`
+mergingIntList:
+`),
+		},
+	},
+	{
+		Description: "$deleteFromPrimitiveList on nonexistent primitive list should not add the primitive list",
+		StrategicMergePatchRawTestCaseData: StrategicMergePatchRawTestCaseData{
+			Original: []byte(`
+foo:
+  - bar
+`),
+			TwoWay: []byte(`
+$deleteFromPrimitiveList/mergingIntList:
+  - 3
+`),
+			Modified: []byte(`
+foo:
+  - bar
+`),
+		},
+	},
 }
 
 func TestCustomStrategicMergePatch(t *testing.T) {