Mapping to insert comment at the end of a line

Question

I'm currently writing a plugin to quickly appends commented TODO: codetags to the end of a line in any file type.

How can I make vim make use of it's commenstring feature to append a comment that corresponds to the filetype?

I am currently entering those manually but I feel like there may be a more platform agnostic way to do this...

Here is what some of my maps look like right now:

" Markdown todo's
autocmd FileType markdown nnoremap <buffer> td o<Esc>o<Esc>O[comment]:<Space>#<Space>TODO:<Space>
autocmd FileType markdown nnoremap <buffer> TD 0/TODO:<Enter>kd2j
" Vim todo's
autocmd FileType vim nnoremap <buffer> td A<Space><Space>"TODO:<Space>
autocmd FileType vim nnoremap <buffer> TD 0/"TODO:<Enter>d$
" PHP todo's
autocmd FileType php nnoremap <buffer> td A<Space><Space>//TODO:<Space>
autocmd FileType php nnoremap <buffer> TD j0?//TODO:<Enter>d$
" Javascript todo's
autocmd FileType javascript nnoremap <buffer> td A<Space><Space>//TODO:<Space>
autocmd FileType javascript nnoremap <buffer> TD j0?//TODO:<Enter>d$

Thanks!

Answer 1

You could use a combination of :execute and substitute. The idea would be to use substitute to replace the %s in the commentstring by your TODO and then use execute to forge the content of the mapping.

Your js mapping could be something like this:

nnoremap td :execute "norm! A  " . substitute(&commentstring, '%s', 'TODO ', '')<CR>A

Where

• execute lets you execute a command forged from a concatenation of strings.
• The concatenated strings are
  • norm! A to execute A as in normal mode (The ! is important if your users remaps A)
  • substitute(&commentstring, '%s', 'TODO ', '') is the commentstring with %s replaced by TODO
• <CR> validates the execute command
• The final A allows the user continue to type their comment.

Relevant help topics:

• :h 'commentstring'
• :h :execute
• :h substitute()

You could also have a look at the source code of NERDCommenter to see how they use 'commentstring'.