hashicorp/nomad · error

format error: %v

Error message

format error: %v

What it means

When `nomad plugin status` with CSI plugins is run with -json or -template, csiFormatPlugins renders the plugin list via the shared Format helper. If JSON marshaling or template execution fails, the error is wrapped as "format error".

Source

Thrown at command/plugin_status_csi.go:90

	str, err := c.csiFormatPlugin(plug)
	if err != nil {
		c.Ui.Error(fmt.Sprintf("Error formatting plugin: %s", err))
		return 1
	}

	c.Ui.Output(str)
	return 0
}

func (c *PluginStatusCommand) csiFormatPlugins(plugs []*api.CSIPluginListStub) (string, error) {
	// Sort the output by quota name
	sort.Slice(plugs, func(i, j int) bool { return plugs[i].ID < plugs[j].ID })

	if c.json || len(c.template) > 0 {
		out, err := Format(c.json, c.template, plugs)
		if err != nil {
			return "", fmt.Errorf("format error: %v", err)
		}
		return out, nil
	}

	rows := make([]string, len(plugs)+1)
	rows[0] = "ID|Provider|Controllers Healthy/Expected|Nodes Healthy/Expected"
	for i, p := range plugs {
		rows[i+1] = fmt.Sprintf("%s|%s|%d/%d|%d/%d",
			limit(p.ID, c.length),
			p.Provider,
			p.ControllersHealthy,
			p.ControllersExpected,
			p.NodesHealthy,
			p.NodesExpected,
		)
	}
	return formatList(rows), nil
}

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Test the template with plain output first (`nomad plugin status <id>`) to confirm the data shape, then fix template field names.
2. Validate template syntax — missing {{end}}, bad pipelines, undefined functions.
3. Use -json alone to see the exact structure before writing a template.
4. Keep the wrapped error text after "format error:" to pinpoint the template line.

Example fix

// before
nomad plugin status -template '{{range .Plugins}}{{.ID}}{{end}}'

// after
nomad plugin status -template '{{range .}}{{.ID}}{{end}}'

// render with -json first to confirm data shape before templating
const data = execSync('nomad plugin status -json').toString();
const plugins = JSON.parse(data); // must be an array of CSIPlugin
if (!Array.isArray(plugins)) throw new Error('expected plugin list');

try { out = csiFormatPlugins(plugs) } catch (e) { if (String(e).startsWith('format error')) { console.error('Template invalid for plugin list; test with -json first:', e.message); } throw e; }

When it happens

Trigger: Running `nomad plugin status -json` or `-template '...'` where the template has invalid syntax, references fields that don't exist on []api.CSIPlugin, or JSON output cannot be produced.

Common situations: Typos in template field paths (e.g. {{.Plugins}} when the data is a plain list), wrong template functions, or copying Consul/Vault templates that expect different data shapes.

Related errors

• json format does not support template option.
• Both json and template formatting are not allowed
• error unmarshaling json: %w
• format error: %w
• Error formatting: %w

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/08a5f444481ebbe6. Report an issue: GitHub.