let rootValue;

  if (typeof exportsField === 'string') {
    return new Map([['.', exportsField]]);
  }
Normalise an "exports"-like field by parsing string shorthand and conditions
shorthand at root, and flattening any legacy Node.js <13.7 array values.

See https://nodejs.org/docs/latest-v19.x/api/packages.html#exports-sugar.