Call function with count after performing some normal! level tasks

Question

I have this following function

" copy yanked text to tmux pane
function! Send_to_tmux(count) range
    if (a:firstline == a:lastline)
        execute "normal! \"zyip"
    else
        execute "normal! \"zy"
    endif
    let text = @z
    let text = substitute(text, ';', '\\;', 'g')
    let text = substitute(text, '"', '\\"', 'g')
    let text = substitute(text, '\n', '" Enter "', 'g')
    let text = substitute(text, '!', '\\!', 'g')
    let text = substitute(text, '%', '\\"', 'g')
    let text = substitute(text, '#', '\\#', 'g')
    silent execute "!tmux send-keys -t " . a:count . " \"" . text . "\""
    silent execute "!tmux send-keys -t " . a:count . "Enter"
endfunction
nnoremap <leader>cc :<C-u>call Send_to_tmux(v:count1)<cr>
xnoremap <leader>cc :<C-u>call Send_to_tmux(v:count1)<cr>

Originally, I didn't use the range attribute in the function and mapped it like this

nnoremap <leader>cc "zyip:<C-u>call Send_to_tmux(v:count1)<cr>
xnoremap <leader>cc "zy:<C-u>call Send_to_tmux(v:count1)<cr>

But this didn't work with the count, that's why I put the if else check for checking if the function was called for visual selection mode.

It does the work, but seems counter intuitive. Is it alright? Is there any other way to call functions with count but do some yanking etc. before calling the function?

Answer 1

I've ran into this exact issue many times. The same problem comes up with v:reg as well. In general, there's two main solutions.

1. Do what you did. Like you said, this isn't always the most convenient solution. Thankfully, there's...

2. Use an <expr> mapping. In general, this means that your mapping is an expression that evaluates to a string, rather than some static string. This can be really useful when your mapping isn't identical every time you use it (for example, if the v:count1 varies). In your case, this would look like:

   nnoremap <expr> <leader>cc '"zyip:\<C-u>call Send_to_tmux('.v:count1.')\<cr>'
   xnoremap <expr> <leader>cc '"zy:\<C-u>call Send_to_tmux('.v:count1.')\<cr>'
   

Some general notes on this approach... Even though this is more convenient, building the string can be a bit of a pain. Especially if the mapping you want has weird characters, quotes or backslashes. Note that in vimscript, "\<C-u>" evaluates to the unprintable ^u (0x15, ctrl-u). But '\<C-u>' evaluates to the literal text \<C-u>. So you'll have to be careful about which quotes you use.