From 5cd11c97cb15ff3500747c838c99cd17d93d306b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sergen=20Yal=C3=A7=C4=B1n?= <yalcinsergen97@gmail.com>
Date: Tue, 6 Feb 2024 19:10:54 +0300
Subject: [PATCH] Add a nil case to the getValueFromInterface function
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Signed-off-by: Sergen Yalçın <yalcinsergen97@gmail.com>
---
 pkg/fieldpath/paved.go      | 27 ++++++++++++++++-----------
 pkg/fieldpath/paved_test.go |  8 ++++++++
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/pkg/fieldpath/paved.go b/pkg/fieldpath/paved.go
index 908187dd5..3283e5676 100644
--- a/pkg/fieldpath/paved.go
+++ b/pkg/fieldpath/paved.go
@@ -112,7 +112,9 @@ func (p *Paved) getValue(s Segments) (any, error) {
 	return getValueFromInterface(p.object, s)
 }
 
-func getValueFromInterface(it any, s Segments) (any, error) {
+func getValueFromInterface(it any, s Segments) (any, error) { //nolint:gocyclo // See note below.
+	// Although the complexity of the function may seem high, in fact the same
+	// operation is performed in different cases.
 	for i, current := range s {
 		final := i == len(s)-1
 		switch current.Type {
@@ -129,18 +131,21 @@ func getValueFromInterface(it any, s Segments) (any, error) {
 			}
 			it = array[current.Index]
 		case SegmentField:
-			object, ok := it.(map[string]any)
-			if !ok {
+			switch object := it.(type) {
+			case map[string]any:
+				v, ok := object[current.Field]
+				if !ok {
+					return nil, errNotFound{errors.Errorf("%s: no such field", s[:i+1])}
+				}
+				if final {
+					return v, nil
+				}
+				it = object[current.Field]
+			case nil:
+				return nil, errNotFound{errors.Errorf("field %q is not found in the path", s[:i])}
+			default:
 				return nil, errors.Errorf("%s: not an object", s[:i])
 			}
-			v, ok := object[current.Field]
-			if !ok {
-				return nil, errNotFound{errors.Errorf("%s: no such field", s[:i+1])}
-			}
-			if final {
-				return v, nil
-			}
-			it = object[current.Field]
 		}
 	}
 
diff --git a/pkg/fieldpath/paved_test.go b/pkg/fieldpath/paved_test.go
index 91bc5e256..e98dad89d 100644
--- a/pkg/fieldpath/paved_test.go
+++ b/pkg/fieldpath/paved_test.go
@@ -161,6 +161,14 @@ func TestGetValue(t *testing.T) {
 				err: errors.Wrap(errors.New("unexpected ']' at position 5"), "cannot parse path \"spec[]\""),
 			},
 		},
+		"NilValue": {
+			reason: "Requesting for an object that has nil value",
+			path:   "spec.containers[*].name",
+			data:   []byte(`{"spec":{"containers": null}}`),
+			want: want{
+				err: errNotFound{errors.Errorf("field %q is not found in the path", "spec.containers")},
+			},
+		},
 	}
 
 	for name, tc := range cases {