argoproj/argo-workflows · error

cannot unmarshal type %T

Error message

cannot unmarshal type %T

What it means

MustUnmarshal accepts only byte slices and strings (optionally prefixed with '@file', '{' for JSON); any other Go type passed as text reaches this panic in the default branch. It is a programmer-error guard for callers of MustUnmarshal (e.g. template expression handling) that pass an unsupported type such as an int or a struct; it panics rather than returning an error.

Source

Thrown at pkg/apis/workflow/v1alpha1/marshall.go:41

		switch x[0] {
		case '@':
			filename := string(x[1:])
			y, err := os.ReadFile(filepath.Clean(filename))
			if err != nil {
				panic(fmt.Errorf("failed to read file %s: %w", filename, err))
			}
			MustUnmarshal(y, v)
		case '{':
			if err := json.Unmarshal(x, v); err != nil {
				panic(fmt.Errorf("failed to unmarshal JSON %q: %w", string(x), err))
			}
		default:
			if err := yaml.UnmarshalStrict(x, v); err != nil {
				panic(fmt.Errorf("failed to unmarshal YAML %q: %w", string(x), err))
			}
		}
	default:
		panic(fmt.Errorf("cannot unmarshal type %T", text))
	}
}

func MustMarshallJSON(v any) string {
	data, err := json.Marshal(v)
	if err != nil {
		panic(err)
	}
	return string(data)
}

func MustUnmarshalClusterWorkflowTemplate(text any) *ClusterWorkflowTemplate {
	x := &ClusterWorkflowTemplate{}
	MustUnmarshal(text, &x)
	return x
}

func MustUnmarshalCronWorkflow(text any) *CronWorkflow {

View on GitHub (pinned to 35bff19146)

Solutions

1. Pass a string or []byte to MustUnmarshal
2. Convert the value (e.g. fmt.Sprint) before calling

When it happens

Trigger: Thrown at pkg/apis/workflow/v1alpha1/marshall.go:41 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of argoproj/argo-workflows@35bff19146 (2026-09-03). Data as JSON: /api/errors/99dbe9bfbce50366. Report an issue: GitHub.