def endpoint(self) -> str | None:
        """The endpoint that matched the request URL.

        This will be ``None`` if matching failed or has not been
        performed yet.

        This in combination with :attr:`view_args` can be used to
        reconstruct the same URL or a modified URL.
        """
        if self.url_rule is not None:
            return self.url_rule.endpoint  # type: ignore[no-any-return]

        return None
The endpoint that matched the request URL.

        This will be ``None`` if matching failed or has not been
        performed yet.

        This in combination with :attr:`view_args` can be used to
        reconstruct the same URL or a modified URL.
        
src/flask/wrappers.py