istio/istio · error

invalid format, expected one of %v but got %q

Error message

invalid format, expected one of %v but got %q

What it means

Print renders analysis/diagnostic messages in the requested output format and rejects anything outside the supported set (log, json, yaml — from MsgOutputFormatKeys). This is the istioctl `--output` / -o flag validator for analyze-style message output.

Source

Thrown at istioctl/pkg/util/formatting/formatter.go:60

)

func init() {
	for _, key := range MsgOutputFormatKeys {
		MsgOutputFormats[key] = true
	}
}

// Print output messages in the specified format with color options
func Print(ms diag.Messages, format string, colorize bool) (string, error) {
	switch format {
	case LogFormat:
		return printLog(ms, colorize), nil
	case JSONFormat:
		return printJSON(ms)
	case YAMLFormat:
		return printYAML(ms)
	default:
		return "", fmt.Errorf("invalid format, expected one of %v but got %q", MsgOutputFormatKeys, format)
	}
}

func printLog(ms diag.Messages, colorize bool) string {
	logOutput := make([]string, 0, len(ms))
	for _, m := range ms {
		logOutput = append(logOutput, render(m, colorize))
	}
	return strings.Join(logOutput, "\n")
}

func printJSON(ms diag.Messages) (string, error) {
	jsonOutput, err := json.MarshalIndent(ms, "", "\t")
	return string(jsonOutput), err
}

func printYAML(ms diag.Messages) (string, error) {
	yamlOutput, err := yaml.Marshal(ms)

View on GitHub (pinned to 8dc789c5cf)

Solutions

1. Use one of the printed valid keys: log, json, or yaml.
2. If you need machine-readable output for analysis results, use `-o json` or `-o yaml` and post-process with jq/yq.
3. Check MsgOutputFormatKeys in the istioctl version in use — the valid set is printed in the error.

Example fix

# before
istioctl analyze -o wide

# after
istioctl analyze -o json

valid := map[string]bool{"log": true, "json": true, "yaml": true}
if !valid[format] {
    return fmt.Errorf("unsupported format %q; use log|json|yaml", format)
}

func IsValidMsgOutputFormat(f string) bool {
    for _, k := range formatting.MsgOutputFormatKeys {
        if f == k { return true }
    }
    return false
}

When it happens

Trigger: Passing an unsupported -o value to commands that route through this Print (e.g. `istioctl analyze -o table`, `-o wide`, `-o xml`) — only log/json/yaml are accepted here, unlike kubectl's richer format set.

Common situations: Muscle memory from kubectl (`-o wide`, `-o name`, `-o jsonpath=...`) applied to istioctl analyze; scripts assuming table output is a valid format string.

Related errors

• filename not specified (see --filename or -f)
• invalid level option
• output format %q not supported
• pattern %s did not match
• metrics requires workload name

AI-assisted analysis of istio/istio@8dc789c5cf (2026-08-15). Data as JSON: /api/errors/d72506b421a1b96d. Report an issue: GitHub.