Have backspace delete whole tabs

Question

Under regular conditions, the tab key will insert a tab character and backspacing that tab deletes the whole tab character.

I have set up expandtab and softtabstop=4 so that when I hit tab it will insert 4 spaces and when I hit "ctrl-v-tab" it will insert a real tab. However, when I backspace real tabs, it will convert it to spaces and delete only 4 of those, leaving 4 behind (apparently backspace behavior is also affected by the softtabstop setup).

How can I set it up so that tab always deletes the whole tab character?

Answer 1

For kicks and because I'm trying to learn some Vim scripting here is a more elaborate solution.

This will handle backspace the way you expect, even if cursor is in first column (in which case it will join with the preceding line).

First add this to your vimrc:

" Sends equivalent of backspace key in Insert mode unless preceding
" character is a Tab in which case a Normal mode 'X' is sent. Allows
" backspace to completely delete Tab even if 'softtabstop' is set to
" a value less than the 'tabstop' setting
function! SmartBackSpace()
  if getline('.')[col('.') - 2] == "\<Tab>"
    normal! X
  else
    call feedkeys("\<C-H>")
  endif
endfunction

Then add this mapping:

inoremap <BS> <C-\><C-O>:call SmartBackSpace()<CR>

It's important that you use this because you need <C-\><C-O> instead of <C-O>. Otherwise the cursor may jump to undesirable places when transitioning from Insert mode to Normal mode.

Answer 2

This mapping will take you out of Insert mode briefly and delete the previous character with 'X' rather than backspace before re-entering Insert mode:

inoremap <BS> <C-\><C-O>X

It seems to do the trick for most cases though there may be some edge cases not yet discovered. If there are too many issues I imagine mapping backspace to a simple function that looks at the previous character before deciding whether to use X or BS. That's the only way, for example, that you could retain the ability of backspace to "unwrap" or delete from the beginning of a line to end of the previous line and such which folks often enable in their vimrc files with lines like set backspace=eol,start,indent

Note: I first suggested something like this mapping in a comment but I hadn't accounted for the cursor movement wonkiness when entering Normal mode (in the middle of the line behaves differently from the end of the line). The Ctrl-\ should take care of it.