Vim stop comment continuation during abbrev expansion

Question

If your Vim settings include 'r' in 'formatoptions' (default) it will automatically insert the current comment leader after hitting [Enter] in insert mode, but this can be undesirable for abbrevs that expand to a single-line comment in languages that don't have separate single/multi-line comment characters.

How do I stop getting this when I press [Enter] after typing the abbrev characters?

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Answer 1

This is what I did:

" Eat one character matching the given regex from the input stream, e.g. at                                 
" the end of an abbr expansion.  (From :help abbreviations)              
func Eatchar(pat)                                    
    let c = nr2char(getchar(0))                        
    return (c =~ a:pat) ? '' : c                       
endfunc                                              

set pastetoggle=<F12>
iabbr <silent> sep # ========<F12><CR><F12><C-R>=Eatchar('\r')<CR>

This replaces the user's [Enter] key press with a generated one surrounded by generated key presses that turn paste mode off before and back on afterwards. The final <CR> completes the <CR>= sequence.