Why is this custom spacemacs major mode keybinding not working?

Question

In .spacemacs I am trying to define a few custom, major mode mappings, that can be accesed using SPC m. This is working fine for org-mode:

  (evil-leader/set-key-for-mode 'org-mode "l" 'org-insert-link)

but when I define it for a different mode it doesn't work:

  (evil-leader/set-key-for-mode 'sclang-mode "sl" 'sclang-eval-line)

Using SPC m just returns SPC m is undefined

UPDATE:

The mode is part of a package that I used following these instructions. In my .spacemacs file I have added these lines to make it work:

(add-to-list 'load-path "~/.emacs.d/sc/el")
(require 'sclang)
(setenv "PATH" (concat (getenv "PATH") ":/Applications/SuperCollider/SuperCollider.app/Contents/Resources"))
(setq exec-path (append exec-path '("/Applications/SuperCollider"  "/Applications/SuperCollider/SuperCollider.app/Contents/Resources" )))

It also required to move a folder in the .emacs.d folder (and I need to remove it temporarily before every spacemacs update...) so yes, definitely not even close to an official layer.

Answer 1

I finally solved this with help from the Spacemacs Gitter channel.

There was a deeper issue with the definition of the major mode itself. More specifically (quoting NJBS's answer on Gitter):

Your issue is that sclang-mode doesn't define itself properly by deriving from fundamental-mode, but rather it defines itself using defun. You can change sclang-mode.el's mode definition to the following and your bindings should stick:

(define-derived-mode sclang-mode fundamental-mode "sclang-mode"
  "Major mode for editing SuperCollider language code.
\\{sclang-mode-map}
"
  (sclang-mode-set-local-variables)
  (sclang-set-font-lock-keywords)
  (sclang-init-document)
  (sclang-make-document))

Link to the commit where I fixed the issue.

Answer 2

Try using:

(spacemacs/set-leader-keys-for-major-mode 'sclang-mode "sl" 'sclang-eval-line)

I am using that on several of my modes and all is displayed properly.

** UPDATE ** The problem you are having is most likely because you are not creating a spacemacs layer, and instead are trying to use the traditional Emacs way of configuration.

To add this to your configuration, you need to create a custom layer. This is the Spacemacs way.

Have a look here for help: https://github.com/syl20bnr/spacemacs/blob/master/doc/LAYERS.org

Answer 3

I think you're likely right that it's an upstream bug, as was the case here:

https://github.com/syl20bnr/spacemacs/issues/6943