kubernetes/kops · error

error marshaling manifest to json: %w

Error message

error marshaling manifest to json: %w

What it means

Object.MarshalJSON marshals the object's underlying generic data map with encoding/json and wraps failures with this error. It exists so kubemanifest.Object can be embedded into other JSON structures; a failure means the data map contains values json.Marshal cannot encode.

Source

Thrown at pkg/kubemanifest/manifest.go:139

		yamls = append(yamls, y)
	}

	return bytes.Join(yamls, yamlSeparator), nil
}

func (m *Object) ToYAML() ([]byte, error) {
	b, err := yaml.Marshal(m.data)
	if err != nil {
		return nil, fmt.Errorf("error marshaling manifest to yaml: %w", err)
	}
	return b, nil
}

func (m *Object) MarshalJSON() ([]byte, error) {
	b, err := json.Marshal(m.data)
	if err != nil {
		return nil, fmt.Errorf("error marshaling manifest to json: %w", err)
	}
	return b, nil
}

func (m *Object) accept(visitor Visitor) error {
	err := visit(visitor, m.data, []string{}, func(v interface{}) {
		klog.Fatal("cannot mutate top-level data")
	})
	return err
}

// IsEmptyObject checks if the object has no keys set (i.e. `== {}`)
func (m *Object) IsEmptyObject() bool {
	return len(m.data) == 0
}

// Kind returns the kind field of the object, or "" if it cannot be found or is invalid
func (m *Object) Kind() string {

View on GitHub (pinned to 4c8573c808)

Solutions

1. Inspect the data map for non-JSON-encodable values (funcs, channels, cycles) and remove/convert them
2. Use the wrapped error to locate the offending value
3. Re-parse the manifest from source YAML to get a clean data map
4. If custom values are needed, give them MarshalJSON implementations

if _, err := json.Marshal(obj.Data()); err != nil {
	return fmt.Errorf("object not JSON-encodable: %w", err)
}

out, err := json.Marshal(structWithEmbeddedObject)
if err != nil && strings.Contains(err.Error(), "marshaling manifest to json") {
	return fmt.Errorf("embedded manifest object is not JSON-encodable: %w", err)
}

When it happens

Trigger: Using kubemanifest.Object as a field in a struct being json.Marshal'ed (e.g. addon manifests serialized into other output) while its data contains unencodable values such as channels, funcs, or cyclic references.

Common situations: Embedding parsed manifests in JSON output/debug dumps; programmatic mutation injecting Go values that aren't JSON encodable.

Understand the failure class

Background: json.Marshal / "failed to marshal" errors in Go: why "unsupported type" happens and how to fix it — this error's family across 22 libraries.

Related errors

• marshalling nodeupConfig: %w
• error marshaling into JSON: %v
• error building annotation patch: %v
• building node patch: %w
• error building node patch: %v

AI-assisted analysis of kubernetes/kops@4c8573c808 (2026-09-05). Data as JSON: /api/errors/6dd42db34539026e. Report an issue: GitHub.