How to bind C-h to delete-backward-char when doing isearch?

Question

I use C-h as an alias for delete-backward-char everywhere.

But when I do isearch it exits the search instead of deleting the character before the cursor.

I tried binding C-h in isearch maps, but that didn't work:

(define-key minibuffer-local-isearch-map (kbd "C-h") 'delete-backward-char)
(define-key isearch-mode-map (kbd "C-h") 'delete-backward-char)

Character gets deleted, but it is deleted in the buffer, not in the isearch prompt.

Is there a way to rebind C-h so it works in isearch prompt?

Answer 1

First, in general, Isearch uses the minibuffer only for M-e. So your minibuffer-local-isearch-map key binding is useless here. That's the keymap used when editing after M-e.

Second, your isearch-mode-map binding means that C-h ends up deleting the char in the buffer you're searching, not deleting a char from the search string. The current buffer remains the buffer you're searching.

This is what you need to do. It defines a command that pops the last char off of the end of the search string.

(defun foo ()
  "Delete last char of the search string."
  (interactive)
  (unless (equal isearch-string "") (isearch-pop-state))
  (isearch-update))

(define-key isearch-mode-map (kbd "C-h") 'foo)