How to set up an execute-once mapping

Question

Autocommands support the ++once modifier. I am trying to achieve the same effect for a map.

Instead of coming up with a general solution I have been trying to solve my particular case via a side-effect – I thought it would be easier...

In this case it's a buffer-local map. The map, in window A, closes window B. To remove the map once it has executed, I have a BufLeave autocmd in window B to remove the map from window A. However I cannot get the autocmd to find the map.

Here's how I set things up in window A:

nnoremap <buffer> <Esc> :<C-U>close_other_window()<CR>
let bufnr = bufnr()
execute "autocmd BufLeave <buffer=".bufnr_of_other_window."> nunmap <buffer=".bufnr."> <Esc>"

The problem is the nunmap cannot find the map. There's no error but the map remains in place. If I use the following instead, it still cannot find the map (perhaps because <buffer> is window B's buffer when the autocmd executes):

execute "autocmd BufLeave <buffer=".bufnr_of_other_window."> nunmap <buffer> <Esc>"

Any tips for this situation or the general case would be appeciated!

Answer 1

Following @statox's comment I found this solution:

nnoremap <buffer> <Esc> :blah<Bar>execute "nunmap <buffer> \e"<CR>

(The \e for <Esc> is in the docs for expr-string.)