How to define multiple key bindings more concisely?

Question

I'm trying to write a helper macro to conveniently define keybindings in my configuration file.

The idea is to replace the following configuration entry:

(use-package org-roam
  :config
  (define-key evil-normal-state-map (kbd "SPC n g") #'org-roam-graph)
  (define-key evil-insert-state-map (kbd "C-c n g") #'org-roam-graph)
  (define-key evil-visual-state-map (kbd "C-c n g") #'org-roam-graph))

With that one:

(use-package org-roam
  :config
  (define-evil-key "n g" #'org-roam-graph))

Here's how I'm trying to write such a macro:

(defmacro define-evil-key (k fn)
  (define-key evil-normal-state-map (kbd (concat "SPC " k)) fn)
  (define-key evil-insert-state-map (kbd (concat "C-c " k)) fn)
  (define-key evil-visual-state-map (kbd (concat "C-c " k)) fn))

But when I press the defined keybinding SPC n g, I get the following error: Wrong type argument: commandp, #'org-roam-graph.

I'm not really sure, what is going wrong. It seems to me, that the macros should be expanded on the sequence of define-key calls, but it doesn't work that way.

Could someone please explain how to properly define this macros and how to debug similar errors in the future?

Answer 1

A macro has to return code. The return value of your macro is whatever the last form evaluated to:

(defmacro define-evil-key (k fn)
  (define-key evil-normal-state-map (kbd (concat "SPC " k)) fn)
  (define-key evil-insert-state-map (kbd (concat "C-c " k)) fn)
  (define-key evil-visual-state-map (kbd (concat "C-c " k)) fn))

(pp-macroexpand-expression '(define-evil-key "x" #'foo))
=> #'foo

Being what the last define-key form had evaluated to.

The specific error "Wrong type argument: commandp, #'org-roam-graph." is related to the fact that macro arguments are not evaluated -- this prevents the define-key calls from binding the intended command.

You wanted something like this:

(defmacro define-evil-key2 (k fn)
  `(progn
     (define-key evil-normal-state-map (kbd ,(concat "SPC " k)) ,fn)
     (define-key evil-insert-state-map (kbd ,(concat "C-c " k)) ,fn)
     (define-key evil-visual-state-map (kbd ,(concat "C-c " k)) ,fn)))

(pp-macroexpand-expression '(define-evil-key2 "x" #'foo))
=> (progn
     (define-key evil-normal-state-map (kbd "SPC x") #'foo)
     (define-key evil-insert-state-map (kbd "C-c x") #'foo)
     (define-key evil-visual-state-map (kbd "C-c x") #'foo))

That said, I see no reason to use a macro for this. I recommend that you make this a function.