feat(wpcarro/emacs): Support struct-update! r/4370

Support mutable variant of `struct-update`. Also remove the `dash` dependency in
`tests.el`.

Change-Id: I76fc809e96b7cbbd3b39fd16db339cb62eab002c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6027
Reviewed-by: wpcarro <wpcarro@gmail.com>
Autosubmit: wpcarro <wpcarro@gmail.com>
Tested-by: BuildkiteCI

1 files changed, 10 insertions, 0 deletions

diff --git a/users/wpcarro/emacs/pkgs/struct/struct.el b/users/wpcarro/emacs/pkgs/struct/struct.el
index 36d9d4ac0b..e5b25c3836 100644
--- a/users/wpcarro/emacs/pkgs/struct/struct.el
+++ b/users/wpcarro/emacs/pkgs/struct/struct.el
@@ -39,6 +39,16 @@ This is immutable."
        (setf (,accessor copy) (funcall ,f (,accessor copy)))
        copy)))
 
+(defmacro struct-update! (type field f xs)
+  "Mutably apply F to FIELD in XS."
+  (let ((accessor (->> field
+                       symbol-name
+                       (s-prepend (s-concat (symbol-name type) "-"))
+                       intern)))
+    `(progn
+       (setf (,accessor ,xs) (funcall ,f (,accessor ,xs)))
+       ,xs)))
+
 (defmacro struct-set (type field x xs)
   "Immutably set FIELD in XS (struct TYPE) to X."
   (let ((copier (->> type