feat(gs/emacs): Set compile-command in nix buffers r/1162

When visiting buffers that represent home-manager or nixos modules, set
compile-command to the relevant switch command.

Change-Id: I565e092d1e6b97eb7fee9d88211c0ee6ebb30b53
Reviewed-on: https://cl.tvl.fyi/c/depot/+/846
Reviewed-by: glittershark <grfn@gws.fyi>

2 files changed, 31 insertions, 0 deletions

diff --git a/users/glittershark/emacs.d/config.el b/users/glittershark/emacs.d/config.el
index c1ff282a3839..fcddf238bc08 100644
--- a/users/glittershark/emacs.d/config.el
+++ b/users/glittershark/emacs.d/config.el
@@ -27,6 +27,7 @@
 (load! "github-org")
 (load! "org-gcal")
 (load! "grid")
+(load! "nix")
 
 (require 's)
 (require 'tvl)
diff --git a/users/glittershark/emacs.d/nix.el b/users/glittershark/emacs.d/nix.el
new file mode 100644
index 000000000000..a5d09f825c17
--- /dev/null
+++ b/users/glittershark/emacs.d/nix.el
@@ -0,0 +1,30 @@
+;;; ~/code/depot/users/glittershark/emacs.d/nix.el -*- lexical-binding: t; -*-
+
+(defun nix-buffer-type ()
+  "Returns:
+
+'home-manager, if the current buffer is a home-manager module
+'nixos, if the current buffer is a nixos module
+nil, if none of the above are the case"
+  (when buffer-file-name
+    (pcase buffer-file-name
+      ((rx (0+ nonl) "system/home" (0+ nonl) ".nix" eos)
+       'home-manager)
+      ((rx (0+ nonl) "system/system" (0+ nonl) ".nix" eos)
+       'nixos))))
+
+(defun set-nix-compile-command ()
+  "Set the compile command for the current buffer based on the type of nix
+buffer it is, per `nix-buffer-type'"
+  (interactive)
+  (when-let ((btype (nix-buffer-type)))
+    (setq-local
+     compile-command
+     (case btype
+       ('home-manager "home-manager switch")
+       ('nixos "sudo nixos-rebuild switch")))))
+
+(add-hook 'nix-mode-hook #'set-nix-compile-command)
+
+(map! (:map nix-mode-map
+       (:n "g SPC" #'compile)))