Interaction with nix-mode: font-lock broken

[ccarlile]

I have my emacs configured as a nix expression. In order to have the elisp sections of the config rendered in emacs lisp mode, I created a polymode to handle the elisp blocks in multi-line nix strings beginning with the string '';;. This breaks fontification in all nix files - syntax highlighting doesn't work until I run e.g. font-lock-debug-fontify. When I disable the polymode, syntax highlighting works as expected. I am not an elisp wizard, so I'm not sure if this is an issue with nix-mode or polymode. I was able to reproduce the issue with a minimal config file and load with emacs -q -l minimal.elisp. The config file is below:

(use-package nix-mode
  :mode "\\.nix\\'")

(use-package polymode
  :config
  (define-hostmode poly-nix-hostmode
    :mode 'nix-mode)
  
  (define-innermode poly-nix-elisp-innermode
    :mode 'emacs-lisp-mode
    :head-matcher "\'\';;"
    :tail-matcher "\'\';"
    :head-mode 'host
    :tail-mode 'host)
  
  (define-polymode poly-nix-mode
    :hostmode 'poly-nix-hostmode
    :innermodes '(poly-nix-elisp-innermode))

  :hook (nix-mode . poly-nix-mode))

If this is an issue with nix-mode, I'm happy to close this and reopen an issue there, but I'm hoping someone can help me figure out where the problem is. Thanks for a great package!

[tylerjl]

Just thought I'd add here that I'm doing something similar - although with a dynamic innermode - and experiencing similar issues. I find that I can often ad-hoc fix things by invoking font-lock with C-x x f to recolor everything, although that isn't ideal. My approach is to derive the inner mode with comments like this:

{
  script = /* sh */ ''
    echo "This is in shell-script-mode"
  '';
}

Here's my config:

(define-hostmode poly-nix-hostmode
  :mode 'nix-mode)
(define-auto-innermode poly-nix-dynamic-innermode
  :head-matcher "/[*] +[[:alpha:]]+ +[*]/ +''$"
  :tail-matcher "^[ \t]+''"
  :mode-matcher (cons "/[*] +\\([[:alpha:]]+\\) +[*]/" 1)
  :head-mode 'host
  :tail-mode 'host)
(define-polymode poly-nix-mode
  :hostmode 'poly-nix-hostmode
  :innermodes '(poly-nix-dynamic-innermode))

(add-to-list 'auto-mode-alist '("\\.nix" . poly-nix-mode))

[ccarlile]

It seems like the issue is with registering the mode in the hook - if I remove the :hook stanza from the use-package config block and invoke poly-nix-mode as a command, then everything works as expected

[uqix]

It seems like the issue is with registering the mode in the hook - if I remove the :hook stanza from the use-package config block and invoke poly-nix-mode as a command, then everything works as expected

Same problem in groovy hostmode with bash innermode.

And with :hook stanza, we can't disable polymode by M-x poly-nix-mode, while manually invoking poly-nix-mode works.

[uqix]

Just thought I'd add here that I'm doing something similar - although with a dynamic innermode - and experiencing similar issues. I find that I can often ad-hoc fix things by invoking font-lock with C-x x f to recolor everything, although that isn't ideal. My approach is to derive the inner mode with comments like this:

{
  script = /* sh */ ''
    echo "This is in shell-script-mode"
  '';
}

Here's my config:

(define-hostmode poly-nix-hostmode
  :mode 'nix-mode)
(define-auto-innermode poly-nix-dynamic-innermode
  :head-matcher "/[*] +[[:alpha:]]+ +[*]/ +''$"
  :tail-matcher "^[ \t]+''"
  :mode-matcher (cons "/[*] +\\([[:alpha:]]+\\) +[*]/" 1)
  :head-mode 'host
  :tail-mode 'host)
(define-polymode poly-nix-mode
  :hostmode 'poly-nix-hostmode
  :innermodes '(poly-nix-dynamic-innermode))

(add-to-list 'auto-mode-alist '("\\.nix" . poly-nix-mode))

Replacing mode-hook with auto-mode-alist works, thanks.