The Default function parameters of JavaScript is overwritten.

[dennougorilla]

  Future<dynamic> getUser([GetUserOptions options]) {
    final Object t = this;
    final _Auth0Client tt = t;
    return promiseToFuture(tt.getUser(options));
  }

I cannot use the default function parameters because the generated code always contains parameters.
If you want to use the defalut function parameter set in the library, you have to remove the parameter from the generated code as a temporary workaround.
return promiseToFuture(tt.getUser());

[dennougorilla]

This may be fine...

  Future<dynamic> getUser([GetUserOptions options]) {
    final Object t = this;
    final _Auth0Client tt = t;
    var result = promiseToFuture(tt.getUser());
    if (options != null) {
      result = promiseToFuture(tt.getUser(options));
    }
    return result;
  }

https://dart.dev/guides/language/language-tour#optional-parameters