affaan-m/ECC · error

No legacy languages were provided

Error message

No legacy languages were provided

What it means

After normalizing and deduplicating options.legacyLanguages, resolveLegacyCompatibilitySelection requires at least one legacy language. If the resulting list is empty the function throws, because a compatibility selection without languages has nothing to resolve. It is a required-argument guard.

Solutions

1. Pass at least one valid legacy language, e.g. legacyLanguages: ['python']
2. Check upstream flag parsing so empty strings are filtered or defaulted
3. Throw/validate a clear error in your own CLI when no language flags are supplied

Example fix

// before
resolveLegacyCompatibilitySelection({ target: 'claude-code', legacyLanguages: [] })
// after
resolveLegacyCompatibilitySelection({ target: 'claude-code', legacyLanguages: ['python'] })

const langs = (options.legacyLanguages ?? []).map(s => String(s).trim()).filter(Boolean);
if (langs.length === 0) {
  throw new Error('at least one legacy language is required');
}

function hasLegacyLanguages(v) {
  return Array.isArray(v) && v.some(x => typeof x === 'string' && x.trim() !== '');
}

try {
  const sel = resolveLegacyCompatibilitySelection(options);
} catch (err) {
  if (err.message === 'No legacy languages were provided') {
    console.error('Usage: --legacy-language <name> (at least one)'); process.exitCode = 2;
  } else throw err;
}

When it happens

Trigger: Calling resolveLegacyCompatibilitySelection() with no legacyLanguages, an empty array [], an array of only empty/whitespace strings that dedupeStrings strips, or legacyLanguages: undefined.

Common situations: Forgetting to pass --legacy-language style CLI flags, parsing flags with a splitter that yields empty strings, or wiring code that forwards an empty config array.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• At least one guided harness must be selected
• No install profile, module IDs, included components, or…
• No install profile, module IDs, or included component IDs…
• all overlays must be readable local files
• all takes must be readable local files

AI-assisted analysis of affaan-m/ECC@8321021c54 (2026-09-16). Data as JSON: /api/errors/9857392e78327f5d. Report an issue: GitHub.

Appendix: source

Thrown at scripts/lib/install-manifests.js:503

    .map(exclusion => ({ ...exclusion }));
}

function resolveLegacyCompatibilitySelection(options = {}) {
  const manifests = loadInstallManifests(options);
  const target = options.target || null;

  if (target && !SUPPORTED_INSTALL_TARGETS.includes(target)) {
    throw new Error(
      `Unknown install target: ${target}. Expected one of ${SUPPORTED_INSTALL_TARGETS.join(', ')}`
    );
  }

  const legacyLanguages = dedupeStrings(options.legacyLanguages)
    .map(language => language.toLowerCase());
  const normalizedLegacyLanguages = dedupeStrings(legacyLanguages);

  if (normalizedLegacyLanguages.length === 0) {
    throw new Error('No legacy languages were provided');
  }

  const unknownLegacyLanguages = normalizedLegacyLanguages
    .filter(language => !Object.hasOwn(LEGACY_LANGUAGE_ALIAS_TO_CANONICAL, language));

  if (unknownLegacyLanguages.length === 1) {
    throw new Error(
      `Unknown legacy language: ${unknownLegacyLanguages[0]}. Expected one of ${listLegacyCompatibilityLanguages().join(', ')}`
    );
  }

  if (unknownLegacyLanguages.length > 1) {
    throw new Error(
      `Unknown legacy languages: ${unknownLegacyLanguages.join(', ')}. Expected one of ${listLegacyCompatibilityLanguages().join(', ')}`
    );
  }

  const canonicalLegacyLanguages = normalizedLegacyLanguages

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