Function getFileProtocolModuleFormat

lib/internal/modules/esm/get_format.js:164–237

* @param {URL} url * @param {{parentURL: string; source?: Buffer}} context * @param {boolean} ignoreErrors * @returns {string}

(url, context = { __proto__: null }, ignoreErrors)

 * @returns {string}
 */
function getFileProtocolModuleFormat(url, context = { __proto__: null }, ignoreErrors) {
  const { source } = context;
  const ext = extname(url);

  if (ext === '.js') {
    const { type: packageType, pjsonPath, exists: foundPackageJson } = getPackageScopeConfig(url);
    if (packageType !== 'none') {
      return packageType;
    }

    // The controlling `package.json` file has no `type` field.
    // `source` is undefined when this is called from `defaultResolve`;
    // but this gets called again from `defaultLoad`/`defaultLoadSync`.
    // For ambiguous files (.js, no type field) we return undefined from `resolve` and re-run the check in `load`.
    const format = detectModuleFormat(source, url);
    if (format === 'module' && foundPackageJson) {
      // This module has a .js extension, a package.json with no `type` field, and ESM syntax.
      // Warn about the missing `type` field so that the user can avoid the performance penalty of detection.
      warnTypelessPackageJsonFile(pjsonPath, url);
    }
    return format;
  }
  if (ext === '.ts' && getOptionValue('--strip-types')) {
    const { type: packageType, pjsonPath, exists: foundPackageJson } = getPackageScopeConfig(url);
    if (packageType !== 'none') {
      return `${packageType}-typescript`;
    }
    // The controlling `package.json` file has no `type` field.
    // `source` is undefined when this is called from `defaultResolve`;
    // but this gets called again from `defaultLoad`/`defaultLoadSync`.
    // Since strip-types depends on detect-module, we always return null if source is undefined.
    if (!source) { return null; }
    const { stringify } = require('internal/modules/helpers');
    const { stripTypeScriptModuleTypes } = require('internal/modules/typescript');
    const stringifiedSource = stringify(source);
    const parsedSource = stripTypeScriptModuleTypes(stringifiedSource, fileURLToPath(url));
    const detectedFormat = detectModuleFormat(parsedSource, url);
    const format = `${detectedFormat}-typescript`;
    if (format === 'module-typescript' && foundPackageJson) {
      // This module has a .js extension, a package.json with no `type` field, and ESM syntax.
      // Warn about the missing `type` field so that the user can avoid the performance penalty of detection.
      warnTypelessPackageJsonFile(pjsonPath, url);
    }
    return format;
  }

  if (ext === '') {
    const packageType = getPackageType(url);
    if (packageType === 'module') {
      return getFormatOfExtensionlessFile(url);
    }
    if (packageType !== 'none') {
      return packageType; // 'commonjs' or future package types
    }

    // The controlling `package.json` file has no `type` field.
    if (!source) {
      return null;