argoproj/argo-workflows · error

failed to read file %s: %w

Error message

failed to read file %s: %w

What it means

MustUnmarshal was given text starting with '@' (a file reference) and os.ReadFile failed for that path. Because this is the Must* helper, the error is raised as a panic — it indicates developer/test misuse or a missing fixture file, not user input.

Source

Thrown at pkg/apis/workflow/v1alpha1/marshall.go:28

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// MustUnmarshal is a utility function to unmarshall either a file, byte array, or string of JSON or YAMl into a object.
// text - a byte array or string, if starts with "@" it assumed to be a file and read from disk, is starts with "{" assumed to be JSON, otherwise assumed to be YAML
// v - a pointer to an object
func MustUnmarshal(text, v any) {
	switch x := text.(type) {
	case string:
		MustUnmarshal([]byte(x), v)
	case []byte:
		if len(x) == 0 {
			panic("no text to unmarshal")
		}
		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)

View on GitHub (pinned to 35bff19146)

Solutions

1. Ensure the referenced file path (after the @) exists
2. Fix the path in the @-prefixed argument or embed the YAML/JSON inline instead

When it happens

Trigger: Thrown at pkg/apis/workflow/v1alpha1/marshall.go:28 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/ee32f55688150775. Report an issue: GitHub.