Sort and annotate 'minibuffer-set-action' completions

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 582236e6de49f17c44c0cf045d05f589537df50a..62c457deb124bb57821a2eb3224a5b580df3aa23 100644 (file)
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1171,6 +1171,7 @@ styles for specific categories, such as files, buffers, etc."
     (multiple-choice (styles . (basic substring)) (sort-function . identity))
     (calendar-month (sort-function . identity))
     (keybinding (sort-function . minibuffer-sort-alphabetically))
+    (function (sort-function . minibuffer-sort-alphabetically))
     (library (sort-function . minibuffer-sort-alphabetically)))
   "Default settings for specific completion categories.
 
@@ -4362,6 +4363,22 @@ possible completions."
           (setq done t)
           (message "Done"))))))
 
+(defun minibuffer--set-action-affixation (cands)
+  "Annotate completion candidates CANDS with their documentation strings."
+  (let ((max (seq-max (cons 0 (mapcar #'string-width cands)))))
+    (mapcar
+     (lambda (cand)
+       (let ((sym (intern cand)))
+         (list cand ""
+               (if-let ((doc (ignore-errors
+                               (documentation sym))))
+                   (concat (make-string (1+ (- max (string-width cand))) ?\s)
+                           (propertize
+                            (substring doc 0 (string-search "\n" doc))
+                            'face 'completions-annotations))
+                 ""))))
+     cands)))
+
 (defvar minibuffer-action-history nil
   "History list for `minibuffer-set-action'.")
 
@@ -4369,7 +4386,12 @@ possible completions."
   "Set minibuffer action function of current minibuffer to ACTION-FN."
   (interactive
    (let ((enable-recursive-minibuffers t))
-     (list (completing-read "Action function: " obarray #'fboundp
+     (list (completing-read "Action function: "
+                            (completion-table-with-metadata
+                             obarray
+                             '((category . function)
+                               (affixation-function . minibuffer--set-action-affixation)))
+                            #'fboundp
                             nil nil 'minibuffer-action-history)))
    minibuffer-mode)
   (when (stringp action-fn) (setq action-fn (read action-fn)))