bug#48694: 28.0.50; Suboptimal autoload cookie for `transient-define-prefix'

[Philipp Stephani <p.stephani2@gmail.com>]

Create this file `test.el' in some directory:

;;; -*- lexical-binding: t; -*-
(require 'transient)
;;;###autoload
(transient-define-prefix f () "test")

Now create autoloads for the directory:

emacs -Q -batch -l transient -l autoload \
  -eval '(setq generated-autoload-file "loaddefs.el")' \
  -f batch-update-autoloads .

Emacs will write the following cookie to loaddefs.el:

(transient-define-prefix f nil "\
test")

That's not optimal:

1. transient-define-prefix isn't autoloaded, so loading this loaddefs
   file will signal an error if `transient' isn't already loaded.

2. Moreover, this is needlessly heavyweight in that it requires
   `transient' to be loaded just for the autoload.  This should rather
   be

   (autoload 'f () "test" "test" t)

   or so.  It's possible to add such an autoload cookie manually, but it
   would be better if Emacs did the right thing automatically.

I think this can be rectified by adding `transient-define-prefix' to the
big list of special/complex cases in `make-autoload'.  However, that in
turn wouldn't be the best solution, because it prevents libraries not
shipped with Emacs from the autoload optimization for defun-like macros
like this.  It would be better to create a macro declaration specifier
that would allow arbitrary defun-like macros to optimize their autoload
behavior.


In GNU Emacs 28.0.50 (build 112, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo version 1.16.0)
 of 2021-05-27
Repository revision: 501296f994ba8b578d8a546eddfd2cdc365305f3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12010000
System Description: Debian GNU/Linux rodete

Configured using:
 'configure --enable-gcc-warnings=warn-only
 --enable-gtk-deprecation-warnings --without-pop --with-mailutils
 --enable-checking=all --enable-check-lisp-object-type --with-modules
 'CFLAGS=-O0 -ggdb3''

Configured features:
CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LIBSELINUX LIBSYSTEMD MODULES NOTIFY INOTIFY PDUMPER PNG SECCOMP SOUND
THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM GTK3 ZLIB

Important settings:
  value of $LC_TIME: en_DK.utf8
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc dired dired-loaddefs rfc822
mml mml-sec epa epg epg-config gnus-util rmail rmail-loaddefs time-date
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils phst skeleton derived edmacro kmacro pcase ffap thingatpt url
url-proxy url-privacy url-expand url-methods url-history url-cookie
url-domsuf url-util url-parse auth-source cl-seq eieio eieio-core
cl-macs eieio-loaddefs password-cache json map url-vars mailcap rx
gnutls puny dbus xml subr-x seq byte-opt gv bytecomp byte-compile cconv
compile text-property-search comint ansi-color ring cl-loaddefs cl-lib
iso-transl tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/x-win x-win term/common-win x-dnd tool-bar
dnd fontset image regexp-opt fringe tabulated-list replace newcomment
text-mode elisp-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock
font-lock syntax font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice button loaddefs faces cus-face macroexp files
window text-properties overlay sha1 md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote threads dbusbind
inotify dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 69310 8044)
 (symbols 48 8422 3)
 (strings 32 24396 1892)
 (string-bytes 1 789482)
 (vectors 16 15089)
 (vector-slots 8 195844 5774)
 (floats 8 26 32)
 (intervals 56 223 0)
 (buffers 992 11))

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