What causes "rest-countries ${label} cannot be empty" in jackwener/OpenCLI?

Pass a non-empty `name` argument to the country command.

jackwener/OpenCLI · error · ArgumentError

rest-countries ${label} cannot be empty

Error message

rest-countries ${label} cannot be empty

What it means

requireString validates that a labeled string argument is non-empty after trimming; otherwise it throws ArgumentError with 'rest-countries ${label} cannot be empty'. It is a guard so commands fail fast with a clear message instead of building malformed URLs. `value ?? ''` means null/undefined also trigger it.

Source

Thrown at clis/rest-countries/utils.js:24

import { ArgumentError, CommandExecutionError, EmptyResultError } from '@jackwener/opencli/errors';

export const REST_COUNTRIES_BASE = 'https://restcountries.com/v3.1';
const UA = 'opencli-rest-countries-adapter/1.0 (+https://github.com/jackwener/opencli; mailto:opencli@example.com)';

// REST Countries valid region values; subregions are validated server-side.
export const REST_COUNTRIES_REGIONS = new Set(['africa', 'americas', 'asia', 'europe', 'oceania', 'antarctic']);

// Fields the adapter always requests; keep this list aligned with `columns` so
// rows never have null-where-absent silent drops.
export const COUNTRY_FIELDS = [
    'name', 'cca2', 'cca3', 'ccn3', 'capital', 'region', 'subregion',
    'population', 'area', 'languages', 'currencies', 'flag', 'latlng', 'timezones',
    'independent', 'unMember', 'landlocked',
].join(',');

export function requireString(value, label) {
    const s = String(value ?? '').trim();
    if (!s) throw new ArgumentError(`rest-countries ${label} cannot be empty`);
    return s;
}

export function requireBoundedInt(value, defaultValue, maxValue, label = 'limit') {
    const raw = value ?? defaultValue;
    const n = typeof raw === 'number' ? raw : Number(raw);
    if (!Number.isInteger(n) || n <= 0) {
        throw new ArgumentError(`rest-countries ${label} must be a positive integer`);
    }
    if (n > maxValue) {
        throw new ArgumentError(`rest-countries ${label} must be <= ${maxValue}`);
    }
    return n;
}

export function requireRegion(value) {
    const raw = String(value ?? '').trim().toLowerCase();
    if (!raw) throw new ArgumentError('rest-countries region is required (e.g. "europe", "asia")');

View on GitHub (pinned to 49907e53dc)

Solutions

Pass a non-empty `name` argument to the country command.
Check the calling script/config for unset or empty variables feeding the name.
Validate required inputs before invoking the command.
Catch ArgumentError and print usage help.

Example fix

// before
await countryCommand({ name: process.env.COUNTRY ?? '' });
// after
if (!process.env.COUNTRY) throw new Error('COUNTRY env var is required');
await countryCommand({ name: process.env.COUNTRY });

Defensive patterns

Strategy: validation

Validate before calling

if (typeof name !== 'string' || name.trim() === '') {
  throw new TypeError('name is required and must be a non-empty string');
}

Type guard

function isNonEmptyString(v) { return typeof v === 'string' && v.trim().length > 0; }

Try / catch

try {
  await countryCommand({ name });
} catch (err) {
  if (err instanceof ArgumentError && /cannot be empty/.test(err.message)) {
    printUsage('name is required');
  } else {
    throw err;
  }
}

Prevention

Validate all required CLI args before invoking commands.
Never pass process.env values directly without an emptiness check.
Default missing required inputs to prompts or hard failures, not ''.
Write integration tests for the missing-argument path.

When it happens

Trigger: Calling the rest-countries country command without a `name` argument, or with name = '' / whitespace / null, so `String(value ?? '').trim()` is empty at clis/rest-countries/utils.js:24.

Common situations: Missing CLI flag or config key; passing an empty environment variable; a script interpolating an unset variable into the name argument.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of jackwener/OpenCLI@49907e53dc (2026-08-29). Data as JSON: /api/errors/88b43b37e090119f. Report an issue: GitHub.