From 7bf8997830872785ce5c020f0498b9f335c06681 Mon Sep 17 00:00:00 2001
From: William Carroll <wpcarro@gmail.com>
Date: Thu, 23 Jan 2020 22:02:13 +0000
Subject: [PATCH] Support nix/sly-from-universe

This function builds a version of SBCL using `nix.buildLisp` and points `sly` to
the built executable. The result is a REPL with access to your project's
dependencies, which is quite useful. One drawback at the moment is that if new
dependencies are added to the project, I think I need to rebuild SBCL using nix
and restart sly.
---
 .../shared/.emacs.d/wpc/packages/wpc-nix.el   | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/configs/shared/.emacs.d/wpc/packages/wpc-nix.el b/configs/shared/.emacs.d/wpc/packages/wpc-nix.el
index af439c442..e2e098308 100644
--- a/configs/shared/.emacs.d/wpc/packages/wpc-nix.el
+++ b/configs/shared/.emacs.d/wpc/packages/wpc-nix.el
@@ -4,9 +4,53 @@
 ;;; Commentary:
 ;; Configuration to support working with Nix.
 
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Dependencies
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+(prelude/assert (f-exists? "~/mono"))
+(prelude/assert (f-exists? "~/depot"))
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Library
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
 ;;; Code:
 (use-package nix-mode
   :mode "\\.nix\\'")
 
+(defun nix/sly-from-universe (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 "*universe-out/%s*" attribute)))
+         (errbuf (get-buffer-create (format "*universe-errors/%s*" attribute)))
+         (expression (format "let depot = import <depot> {}; universe = import <universe> {}; in depot.nix.buildLisp.sbclWith [ universe.%s ]" attribute))
+         (command (list "nix-build" "-E" expression)))
+    (message "Acquiring Lisp for <depot>.%s" attribute)
+    (make-process :name (format "depot-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 <depot>.%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