How to have vnoremap call function once?

Question

I'm trying to write a function + map that works on a visual selection. My function just prints out the marks right now:

let g:count = 0
function! s:plink(...) abort
    let g:count = g:count + 1
    echomsg printf("%d %s %d %s %d", g:count, a:1, line(a:1), a:2, line(a:2))
endfunction
vnoremap <Leader>r :call <SID>plink("'<", "'>")<CR>

I was surprised to find out that my function is being called once per line when I invoke it as shift-V, select lines, \r:

1 '< 80 '> 84
2 '< 80 '> 84
3 '< 80 '> 84
4 '< 80 '> 84
5 '< 80 '> 84

How do I make this snippet call my code only once when I invoke it?

Answer 1

When you start an ex-command (:) from visual mode, Vim automatically prepends '<,'> to the command.

Function calls can accept ranges, of which the above is an example: when given them, they are called once for each line.

One fix is to get rid of the range when the function is called:

xnoremap <Leader>r :<C-u>call ...

(Note that I’ve switched to xnoremap to only map in visual mode—vnoremap includes select mode, which generally is undesirable.)

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The alternative is to declare the function with the range attribute (see :help func-range).

Then the mapping is unchanged, but the declaration must take two arguments (a:firstline and a:lastline).