Function resolveAsCommonJS

lib/internal/modules/esm/resolve.js:888–936

* Try to resolve an import as a CommonJS module. * @param {string} specifier - The specifier to resolve. * @param {string} parentURL - The base URL. * @returns {string | Buffer | false}

(specifier, parentURL)

 * @returns {string | Buffer | false}
 */
function resolveAsCommonJS(specifier, parentURL) {
  try {
    const { Module: CJSModule } = require('internal/modules/cjs/loader');
    const parent = fileURLToPath(parentURL);
    const tmpModule = new CJSModule(parent, null);
    tmpModule.paths = CJSModule._nodeModulePaths(parent);

    let found = CJSModule._resolveFilename(specifier, tmpModule, false);

    // If it is a relative specifier return the relative path
    // to the parent
    if (isRelativeSpecifier(specifier)) {
      const foundURL = pathToFileURL(found).pathname;
      found = relativePosixPath(
        StringPrototypeSlice(parentURL, 'file://'.length, StringPrototypeLastIndexOf(parentURL, '/')),
        foundURL);

      // Add './' if the path does not start with '../'
      // This should be a safe assumption because when loading
      // esm modules there should be always a file specified so
      // there should not be a specifier like '..' or '.'
      if (!StringPrototypeStartsWith(found, '../')) {
        found = `./${found}`;
      }
    } else if (isBareSpecifier(specifier)) {
      // If it is a bare specifier return the relative path within the
      // module
      const i = StringPrototypeIndexOf(specifier, '/');
      const pkg = i === -1 ? specifier : StringPrototypeSlice(specifier, 0, i);
      const needle = `${sep}node_modules${sep}${pkg}${sep}`;
      const index = StringPrototypeLastIndexOf(found, needle);
      if (index !== -1) {
        found = pkg + '/' + ArrayPrototypeJoin(
          ArrayPrototypeMap(
            StringPrototypeSplit(StringPrototypeSlice(found, index + needle.length), sep),
            // Escape URL-special characters to avoid generating a incorrect suggestion
            encodeURIComponent,
          ),
          '/',
        );
      } else {
        found = `${pathToFileURL(found)}`;
      }
    }
    return found;
  } catch {
    return false;
  }
}

/**
 * Validate user-input in `context` supplied by a custom loader.