argoproj/argo-workflows · error

failed to unmarshal JSON %q: %w

Error message

failed to unmarshal JSON %q: %w

What it means

MustUnmarshal detected leading '{' so treated the input as JSON, but json.Unmarshal failed. The message includes the offending text; MustUnmarshal panics with this wrapped error, signalling malformed JSON passed to a test/dev helper.

Source

Thrown at pkg/apis/workflow/v1alpha1/marshall.go:33

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)
	if err != nil {
		panic(err)
	}
	return string(data)
}

View on GitHub (pinned to 35bff19146)

Solutions

1. Fix the JSON syntax (quotes, commas, brackets) in the input
2. Pass valid YAML (non-'{' leading) or a file reference instead

When it happens

Trigger: Thrown at pkg/apis/workflow/v1alpha1/marshall.go:33 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/b5a1c46694dbee4d. Report an issue: GitHub.