Regression:  transient prompt has blank line after it if the input line is the width of the terminal

Is there any way to get the current input buffer outside a keybinding function? That means [`rl_buffer:getbuffer`][rl_buffer_getbuffer] is not available in the context. If it's not possible now, will it be supported in the future?

[rl_buffer_getbuffer]: https://chrisant996.github.io/clink/clink.html#rl_buffer:getbuffer