tvl-depot/emacs/.emacs.d/wpc/wpc-nix.el
William Carroll 837cfe07c7 Rename dotfiles -> briefcase
Renaming my mono-repo briefcase.

I first introduced this commit in master, but it introduced a bug where one of
two things would happen:

1. Emacs wouldn't start and would crash X.
2. Emacs would start but my keyboard wouldn't work.

I learned some valuable debugging skills in the process. Here are some of them:

When my keyboard was broken, I wanted to control my computer using my
laptop. Thankfully this is possible by using `x2x`, which forward X events from
the SSH client to the SSH host.

```shell
> # I'm unsure if this is the *exact* command
> ssh -X desktop x2x -west :0.0
```

Git commit-local bisecting. I didn't need to do a `git bisect` because I knew
which commit introduced the bug; it was HEAD, master. But -- as you can see from
the size of this commit -- there are many changes involved. I wanted to binary
search through the changes, so I did the following workflow using `magit`:

- git reset --soft HEAD^
- git stash 1/2 of the files changed
- re-run `nix-env -f ~/briefcase/emacs -i`
- restart X session
- If the problem persists, the bug exists in the non-stashed files. Repeat the
  process until you find the bug.

In my case, the bug was pretty benign. Calling `(exwm/switch "Dotfiles")` at the
bottom of `window-manager.el` was failing because "Dotfiles" is the name of a
non-existent workspace; it should've been `(exwm/switch "Briefcase")`.

There may have been more problems. I changed a few other things along the way,
including exposing the env vars BRIEFCASE to `wpcarros-emacs` inside of
`emacs/default.nix`.

The important part is that this was a valuable learning opportunity, and I'm
glad that I'm walking away from the two days of "lost productivity" feeling
actually productive.
2020-01-31 15:27:48 +00:00

58 lines
2.5 KiB
EmacsLisp

;;; wpc-nix.el --- Nix support -*- lexical-binding: t -*-
;; Author: William Carroll <wpcarro@gmail.com>
;;; Commentary:
;; Configuration to support working with Nix.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Dependencies
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; TODO: These may fail at startup. How can I make sure that the .envrc is
;; consulted when Emacs starts?
(prelude/assert (f-exists? (getenv "BRIEFCASE")))
(prelude/assert (f-exists? (getenv "DEPOT")))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Library
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Code:
(use-package nix-mode
:mode "\\.nix\\'")
(defun nix/sly-from-briefcase (attribute)
"Start a Sly REPL configured with a Lisp matching a derivation
from my monorepo.
This function was taken from @tazjin's depot and adapted for my monorepo.
The derivation invokes nix.buildLisp.sbclWith and is built
asynchronously. The build output is included in the error
thrown on build failures."
(interactive "sAttribute: ")
(lexical-let* ((outbuf (get-buffer-create (format "*briefcase-out/%s*" attribute)))
(errbuf (get-buffer-create (format "*briefcase-errors/%s*" attribute)))
(expression (format "let depot = import <depot> {}; briefcase = import <briefcase> {}; in depot.nix.buildLisp.sbclWith [ briefcase.%s ]" attribute))
(command (list "nix-build" "-E" expression)))
(message "Acquiring Lisp for <briefcase>.%s" attribute)
(make-process :name (format "nix-build/%s" attribute)
:buffer outbuf
:stderr errbuf
:command command
:sentinel
(lambda (process event)
(unwind-protect
(pcase event
("finished\n"
(let* ((outpath (s-trim (with-current-buffer outbuf (buffer-string))))
(lisp-path (s-concat outpath "/bin/sbcl")))
(message "Acquired Lisp for <briefcase>.%s at %s" attribute lisp-path)
(sly lisp-path)))
(_ (with-current-buffer errbuf
(error "Failed to build '%s':\n%s" attribute (buffer-string)))))
(kill-buffer outbuf)
(kill-buffer errbuf))))))
(provide 'wpc-nix)
;;; wpc-nix.el ends here