How to suppress a minor mode's key binding in only certain major modes?

Question

Suppose that I use minor mode MIN with a whole bunch of major modes. In one of those major modes, call it MAJ1, MIN's binding for a specific key K is undesirable; I would therefore like to suppress that definition and get Emacs to fall back to either the major mode's definition, if any, or the default in global-map. However, I don't want to change how MIN handles that key when it's used with any other major mode, and I want to preserve MIN's other effects in MAJ1. What's the best way to accomplish that?

The specific combination I'm concerned with is Typo minor mode + Markdown major mode (these are both installed as ELPA packages) and the printable character ` (ASCII backtick), which is syntactically significant in Markdown. typo-mode defines ` to insert ‘ (left single quote) and then replace that with a backtick if pressed again. 99% of the time when I type ` in a markdown file I want the ASCII backtick, so I want to get rid of the typo-mode binding, but only when the major mode is markdown-mode.

Typo mode is activated from text-mode-hook:

(add-hook 'text-mode-hook
          #'(lambda ()
              (auto-fill-mode 1)
              (typo-mode 1)))

The obvious place to put a markdown-specific override is markdown-mode-hook, so I tried

(add-hook 'markdown-mode-hook
          #'(lambda ()
              (local-set-key (kbd "`") 'self-insert-command)))

but that seems to have no effect at all; I'm guessing that the typo-mode keymap only gets applied after markdown-mode-hook finishes.

Complicating matters, markdown-mode has optional electric behavior for `, so ideally what I would be doing is punching a markdown-specific hole in the typo-mode keymap to allow the markdown-mode-map binding to take effect for this key, but if there's no good way to do that, I could live with a solution that just gets it bound to self-insert-command.

Answer 1

I don't think there's an easy way out for this one. You might do something like:

(add-hook 'typo-mode-hook
          (lambda ()
            (when (and typo-mode (derived-mode-p 'markdown-mode))
              (let ((map (make-sparse-keymap)))
                (set-keymap-parent map typo-mode-map)
                (define-key map (kbd "`") 'self-insert-command)
                (push `(typo-mode . ,map)
                      minor-mode-overriding-map-alist)))))

Answer 2

While this is not a general-purpose solution, future readers might like to know that typo-mode has a hook typo-disable-electricity-functions that can be used to solve the specific case of not wanting typo's behavior for some keys in some major modes. Here's what I have been using for a while now:

(defun zw-typo-inappropriate-electricity-for-markdown ()
  "Hook for typo-disable-electricity-functions: Typographical
punctuation is desirable in Markdown mode, but should be disabled
if we are inside code (either inline or block), and the typo-mode
binding for ` should be disabled altogether."
  (and (derived-mode-p 'markdown-mode)
       (or (eq last-command-event ?`)
           (markdown-inline-code-at-point-p)
           (markdown-code-block-at-point-p))))

(add-hook 'typo-disable-electricity-functions
          'zw-typo-inappropriate-electricity-for-markdown)

(The predicates markdown-inline-code-at-point-p and markdown-code-block-at-point-p are defined by current versions of markdown-mode.)