[BUG] Second item of `org-agenda-timerange-leaders' cannot be a function [9.4.6 (9.4.6-gf70e36 @ /home/viz/lib/emacs/straight/build/org/)]

[BUG] Second item of `org-agenda-timerange-leaders' cannot be a function [9.4.6 (9.4.6-gf70e36 @ /home/viz/lib/emacs/straight/build/org/)]

[Visuwesh via General discussions about Org-mode.]

Looking at the definition of `org-agenda-timerange-leaders' suggests
that the second item of the list can be a function.

    (defcustom org-agenda-timerange-leaders '("" "(%d/%d): ")
      "Text preceding timerange entries in the agenda view.
    This is a list with two strings.  The first applies when the range
    is entirely on one day.  The second applies if the range spans several days.
    The strings may have two \"%d\" format specifiers which will be filled
    with the sequence number of the days, and the total number of days in the
    range, respectively."
      :group 'org-agenda-line-format
      :type '(list
          (string :tag "Deadline today   ")
          (choice :tag "Deadline relative"
              (string :tag "Format string")
              (function))))
                ^^^

However, setting it to a function simply yields a type error since
`format' expects a string.  This has been a problem ever since the
option was introduced in the commit ea258dbdb.  

It would be nice if org could accept a function, as one would expect 
from the definition of the concerned option.  The function would accept two arguments and return a format-string or a _formatted_ string?

Regards.

P.S. Please add me to CCs since I don't follow the mailing list.