remap to a map calling getchar() internally

Question

I want to extend the easymotion Plugin to take some action after the jump. To explain to those who are not familiar with this plugin, I will use the following simplified example.

Say in a plugin UsefulPlugin the following map is defined:

function! s:Goto()
    let char = nr2char(getchar())
    return "f" . char
endfunction
nnoremap <expr> <Plug>(goto) s:Goto()

which does almost the same as the unmapped f: jump to the next char input by getchar.

Now as a user, I want to define a map that uses <Plug>(goto) and after the user input the char, jump to that char and delete until end of line. As an illustration: the effect of this mapping should be equivalent to

function! s:GotoAndMore()
    let char = nr2char(getchar())
    return "f" . char . "D"
endfunction
nnoremap <expr> fD s:GotoAndMore()

My question is: how can I achieve this with <Plug>(goto)?

Answer 1

This is hackish and I'm not sure how this works if s:Goto calls another script-internal function.

I assume that the s:Goto() is already defined in another script.

function! GotoAndMore()
    " Get the mapping for <Plug>(goto)
    redir => xx | silent map <Plug>(goto) | redir end
    " extract the function name (incl script number)
    let funcName = matchstr(xx, "<SNR>[^(]*")
    " create a funcref for it
    let Func = function(funcName)
    " return function return value with following "D" 
    return Func() . "D"
endfunction
nnoremap <expr> fD GotoAndMore()

Test thoroughly!