(perf)utils: optimize org-roam-plist-map! (#1958)

The old implementation:

- did not handle duplicate keys well (the function would be applied to each value, but only the first value would be updated with the last value's result)
- was quadratic in the length of the input list (for each key, plist-put would search for the first occurrence of the key by going through all previous elements again)
- copied the input sequence even though this was not really needed
- did not provide a result value that could be useful, thus encouraging imperative programming
- did not need to be a macro, and the macro implementation was evaluating fn multiple times and causing warnings in the native compiler because k and v were not bound.

org-roam-utils.el

@@ -60,17 +60,15 @@ Like `string-equal', but case-insensitive."
            (string-equal (downcase s1) (downcase s2)))))
 
 ;;; List utilities
-(defmacro org-roam-plist-map! (fn plist)
+(defun org-roam-plist-map! (fn plist)
-  "Map FN over PLIST, modifying it in-place."
+  "Map FN over PLIST, modifying it in-place and returning it.
-  (declare (indent 1))
+FN must take two arguments: the key and the value."
-  (let ((plist-var (make-symbol "plist"))
+  (let ((plist-index plist))
-        (k (make-symbol "k"))
+    (while plist-index
-        (v (make-symbol "v")))
+      (let ((key (pop plist-index)))
-    `(let ((,plist-var (copy-sequence ,plist)))
+        (setf (car plist-index) (funcall fn key (car plist-index))
-       (while ,plist-var
+              plist-index (cdr plist-index)))))
-         (setq ,k (pop ,plist-var))
+  plist)
-         (setq ,v (pop ,plist-var))
-         (setq ,plist (plist-put ,plist ,k (funcall ,fn ,k ,v)))))))
 
 ;;; File utilities
 (defmacro org-roam-with-file (file keep-buf-p &rest body)