Change the mapping of F5 on the basis of specific file type

Question

The current mapping of my F5 key is:

imap  :w\\|!python %

Now I want that if I\'m editing any python

Answer 1

Try this:

au BufEnter *.py map <F5> <esc>:w\|!python %<CR>
au BufEnter *.java imap <F5> <esc>:w\|!javac %<CR>
au BufEnter *.c, *.cpp imap <F5> <esc>:w\|!make %<CR>

I'm not 100% sure about the comma separated file types, trying to verify...

The vim docs are usually pretty nasty to try to figure out how to use commands, but these should help get you started:

:h BufEnter
:h :autocmd

Note: You may have to restart vim for these changes to overwrite the current autocommand groups.

Answer 2

There are problems with both given answer and original mapping. First of all, for buffer-local mappings there is *map <buffer>. Second, with <buffer> you don’t need to use BufEnter events and can instead use Filetype which are launched only once. Third, you have one error (2.), one potential problem (1.) and one place that can be optimized in original mappings:

1. you should not be using imap, it makes it very easy to accidentally break old mappings when adding new ones
2. !python % will break once file contain a special symbol (space, semicolon, quot, dollar, …)
3. using :update instead of :write avoids useless writes in some cases

My variant:

autocmd Filetype c,cpp  inoremap <buffer> <F5> <C-o>:update<Bar>execute '!make '.shellescape(expand('%:r'), 1)<CR>
autocmd Filetype python inoremap <buffer> <F5> <C-o>:update<Bar>execute '!python '.shellescape(@%, 1)<CR>
autocmd Filetype java   inoremap <buffer> <F5> <C-o>:update<Bar>execute '!javac '.shellescape(@%, 1)<CR>