Call vim function via mapping fails

Question

I defined the following function, which works fine when called directly:

function EncloseParagraphs()
   execute "normal `>a</p>\<Esc>`<i<p>\<Esc>"
   %s/\%V\n\{2,}\%V/<\/p>\r\r<p>/ge
   nohl
endfunction

But when I use the following mapping

map <silent> <C-P> :call EncloseParagraphs()<CR>

The results look like this

<p><p><p>This is a paragraph.</p></p></p>

<p><p><p>This is a paragraph.</p>
</p></p>

In other words, multiple p tags are added when more than one paragraph is selected in visual mode. Why does the function behave differently when called via the mapped shortcut?

Answer 1

From the Vim help documentation:

help :call

--snip--
When a range is given and the function doesn't handle it
itself, the function is executed for each line in the range,
with the cursor in the first column of that line.  The cursor
is left at the last line (possibly moved by the last function
call).  The arguments are re-evaluated for each line.

Looks like since you're selecting (highlighting) a block of lines then pressing C-P, your function is executed multiple times for that block, once for each line selected.

I imagine you'll need to implement range handling within your function to prevent the multiple execution provided (!) by the :call function.

The remainder of the :call function help documentation discusses how to handle ranges and avoid this problem.