ReactiveX/rxjs · error · Error

Unknown option

Error message

Unknown option: ${argument}

What it means

Thrown by parseArguments when the command line contains a token starting with '-' that does not match any known flag. The CLI rejects unknown options outright rather than silently ignoring them, so misspelled flags fail fast.

Solutions

1. Remove the unsupported flag
2. Check spelling against the --help output
3. Replace with the supported equivalent (e.g. --write instead of --dry-run semantics)

Example fix

# before
npx @rxjs/migrate --dry-run file.ts
# after
npx @rxjs/migrate file.ts   # plan is printed by default; add --write to apply

const KNOWN_FLAGS = new Set(['--source-root','--source-repo','--source-sha','--mode','--framework','--write','--out-dir','--help','-h']);
for (const a of argv) if (a.startsWith('-') && !KNOWN_FLAGS.has(a)) throw new Error(`Unsupported flag in wrapper: ${a}`);

const isKnownFlag = (a: string) => a.startsWith('-') && KNOWN_FLAGS.has(a);

try { runCli(argv); } catch (e) { console.error((e as Error).message); /* prints the exact unknown option */ }

When it happens

Trigger: Passing an unsupported flag such as --dry-run, --verbose, or -v, or a typo like --source-rrot. Any token beginning with '-' that is not in the switch statement hits the default case and throws.

Common situations: Assuming flags from other codemods (jest-codemods, ts-migrate), using short forms that do not exist, or leftover flags in a reused npm script.

Related errors

• requires a value
• --out-dir is required with --write
• Unknown framework
• Unknown mode
• Cannot locate the canonical Skill shipped by @rxjs/migrate.

AI-assisted analysis of ReactiveX/rxjs@54796b38a5 (2026-08-28). Data as JSON: /api/errors/e38f64b619cacc97. Report an issue: GitHub.

Appendix: source

Thrown at packages/migrate/src/cli.ts:158

        if (mode !== 'cold' && mode !== 'platform') throw new Error(`Unknown mode: ${mode}`);
        options.mode = mode;
        break;
      }
      case '--framework': {
        const framework = requiredValue(argv, ++index, argument);
        if (framework !== 'preserve' && framework !== 'mocha-chai-vitest') throw new Error(`Unknown framework: ${framework}`);
        options.framework = framework;
        break;
      }
      case '--write':
        options.write = true;
        break;
      case '--help':
      case '-h':
        options.help = true;
        break;
      default:
        if (argument.startsWith('-')) throw new Error(`Unknown option: ${argument}`);
        options.files.push(argument);
    }
  }
  return options;
}

function validateArguments(options: CliOptions): asserts options is RunnableCliOptions {
  const missing = [
    options.files.length === 0 ? 'at least one source file' : undefined,
    options.sourceRoot ? undefined : '--source-root',
    options.repository ? undefined : '--source-repo',
    options.sha ? undefined : '--source-sha',
  ].filter((value): value is string => value !== undefined);
  if (missing.length > 0) throw new Error(`Missing required argument${missing.length === 1 ? '' : 's'}: ${missing.join(', ')}`);
  if (options.write && !options.outputRoot) throw new Error('--out-dir is required with --write');
}

function requiredValue(argv: readonly string[], index: number, option: string): string {

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