jackwener/OpenCLI · error · ArgumentError

lobsters domain "${value}" is not a valid hostname

Error message

lobsters domain "${value}" is not a valid hostname

What it means

Thrown by requireDomain() when the supplied value fails DOMAIN_PATTERN, which requires at least two dot-separated labels of alphanumeric/hyphen characters with no spaces, scheme, path, or trailing hyphens. The library rejects anything that is not a plain hostname before making a request.

Source

Thrown at clis/lobsters/domain.js:18

// lobsters domain — list Lobste.rs stories submitted from a specific domain.
//
// Hits the public `https://lobste.rs/domains/<domain>.json` endpoint
// (returns the same per-story shape used by `lobsters tag` / `lobsters
// hot`). Lets agents ask "what did Lobsters surface from github.com /
// blog.cloudflare.com / arxiv.org lately?".
import { cli, Strategy } from '@jackwener/opencli/registry';
import { ArgumentError, CommandExecutionError, EmptyResultError } from '@jackwener/opencli/errors';

const DOMAIN_PATTERN = /^[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?(\.[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?)+$/i;

function requireDomain(value) {
    const s = String(value ?? '').trim().toLowerCase();
    if (!s) {
        throw new ArgumentError('lobsters domain is required (e.g. "github.com" or "arxiv.org")');
    }
    if (!DOMAIN_PATTERN.test(s)) {
        throw new ArgumentError(`lobsters domain "${value}" is not a valid hostname`);
    }
    return s;
}

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

cli({
    site: 'lobsters',

View on GitHub (pinned to 49907e53dc)

Solutions

1. Strip scheme, path, and query, leaving only the hostname: new URL(input).hostname
2. Ensure the value has at least two dot-separated labels, e.g. 'arxiv.org' not 'arxiv'
3. Remove surrounding whitespace or stray characters (quotes, trailing slash)
4. If a bare single label like 'localhost' is intended, note this API does not accept it

Example fix

// before
await cli.domain('https://github.com/trending');
// after
await cli.domain(new URL('https://github.com/trending').hostname); // 'github.com'

const DOMAIN_PATTERN = /^[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?(\.[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?)+$/i;
function isValidDomain(v) {
  const s = String(v ?? '').trim().toLowerCase();
  return DOMAIN_PATTERN.test(s);
}
if (!isValidDomain(input)) input = new URL(input).hostname;

function isBareHostname(v) {
  return typeof v === 'string' && /^[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?(\.[a-z0-9]([a-z0-9-]{0,61}[a-z0-9])?)+$/i.test(v.trim());
}

try {
  await cli.domain(input);
} catch (err) {
  if (err instanceof ArgumentError && /not a valid hostname/.test(err.message)) {
    input = new URL(input.startsWith('http') ? input : `https://${input}`).hostname;
    return cli.domain(input);
  }
  throw err;
}

When it happens

Trigger: Passing 'https://github.com', 'github.com/', 'github .com', '-github.com', 'localhost', 'github', or a full URL into domain()/requireDomain().

Common situations: Users paste a full URL copied from the browser instead of the bare domain; trailing slash or path included; subdomain-only shorthand like 'en.wikipedia' lacking a TLD; uppercase is fine (pattern is case-insensitive) but spaces and schemes are not.

Related errors

• coingecko derivatives limit must be a positive integer
• --from and --to must differ (got ${fromCity})
• ${label} must be a positive integer
• ${label} must be an integer >= ${min}
• Invalid HN item id: ${args.id}

AI-assisted analysis of jackwener/OpenCLI@49907e53dc (2026-08-29). Data as JSON: /api/errors/db43e21f9dd2a6c4. Report an issue: GitHub.