Setting to prevent <c-h> to erase text

Question

I have a map which allows me to navigate with hjkl in insert mode:

" In insert or command mode, move normally by using Ctrl
inoremap <C-h> <Left>
inoremap <C-j> <Down>
inoremap <C-k> <Up>
inoremap <C-l> <Right>
cnoremap <C-h> <Left>
cnoremap <C-j> <Down>
cnoremap <C-k> <Up>
cnoremap <C-l> <Right>

All maps works, except <c-h>. In insert mode, when a I press <c-h>, backspace occours. I know that ^H is the ASCII for backspace, but I would like to know if there's some way to make my <c-h> works as <left>.

When I run: :verbose inoremap <c-h> it returns

i  <C-H>       *@<C-R>=AutoPairsDelete()<CR>                                                                                                                            │ost/site/content/themes/sc5
        Last set from ~/.vim/plugged/auto-pairs/plugin/auto-pairs.vim line 549                                                                                          │0k/gulpfile.js
i  <C-H>       * <Left>                                                                                                                                                 │[10:29:37] Starting 'watch'
        Last set from ~/.dotfiles/nvim/init.vim line 264

A courious thing is that in command mode, <c-h> works fine!

I'm using iTerm2 in MacOS Catalina with tmux and neovim.

Answer 1

Thanks to your output of verbose inoremap <c-h> it's really easy to see what is happening here!

You are using the auto-pairs plug-in and it's installing buffer-local mappings for the bracket keys, but also for keys such as Enter and Backspace. It maps backspace so it can "undo" a close bracket action if you type backspace to erase a mistake of yours.

Now, there's actually a difference between <C-h> and "backspace". While historically the backspace key would produce the <C-h> sequence, that's no longer the case and most modern terminal emulators will produce a different sequence for the "backspace" key (unless they're configured to produce the <C-h> sequence for backward compatibility reasons, but that's more and more rare nowadays.)

For historical reasons, auto-pairs (and probably most other plug-ins that map backspace) will by default map <C-h> as well as "backspace", so that if you have an old terminal or have it misconfigured, everything will keep working the same with <C-h> as it does with the "backspace" key.

(It's true that the default action of Vim for <C-h> is the same as backspace, for much of the same reasons.)

Fortunately, auto-pairs allows you to control these two mappings individually, by setting global variables from your vimrc, you have g:AutoPairsMapBS to create the mapping for the backspace key, and g:AutoPairsMapCh to create the mapping for <C-h>.

So you can fix your issue simply by adding this line to your vimrc file:

let g:AutoPairsMapCh = 0