bug#66161: 30.0.50; cperl-mode bug in fontification after __END__

bug#66161: 30.0.50; cperl-mode bug in fontification after __END__

[Mauro Aranda]

emacs -Q
C-x C-f bug.pl
M-x cperl-mode

Enter the following:
#!/usr/bin/perl

use strict;
use warnings;

print("Hello World\n");

__END__

TODO:
What's happening?

It's all messed up.


Fontificacion after __END__ is wrong.


In GNU Emacs 30.0.50 (build 9, x86_64-pc-linux-gnu, GTK+ Version
  3.24.33, cairo version 1.16.0) of 2023-09-21 built on tbb-desktop
Repository revision: 9db3fbd369121ddd34e7f4febe8688d758a5dbb7
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12201001
System Description: Ubuntu 22.04.2 LTS

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY
INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
   value of $LC_MONETARY: es_AR.UTF-8
   value of $LC_NUMERIC: es_AR.UTF-8
   value of $LC_TIME: es_AR.UTF-8
   value of $LANG: en_US.UTF-8
   value of $XMODIFIERS: @im=ibus
   locale-coding-system: utf-8-unix

Major mode: CPerl

Minor modes in effect:
   tooltip-mode: t
   global-eldoc-mode: t
   show-paren-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
   minibuffer-regexp-mode: t
   line-number-mode: t
   indent-tabs-mode: t
   transient-mark-mode: t
   auto-composition-mode: t
   auto-encryption-mode: t
   auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils time-date subr-x
cl-loaddefs cl-lib cperl-mode rx facemenu perl-mode rmc iso-transl
tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-dnd
touch-screen tool-bar dnd fontset image regexp-opt fringe tabulated-list
replace newcomment text-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
nadvice seq simple cl-generic indonesian philippine 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 emoji-zwj charscript charprop
case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp
files window text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget keymap hashtable-print-readable backquote
threads dbusbind inotify lcms2 dynamic-setting system-font-setting
font-render-setting cairo gtk x-toolkit xinput2 x multi-tty move-toolbar
make-network-process emacs)

Memory information:
((conses 16 46308 13707) (symbols 48 6033 0) (strings 32 15859 1563)
  (string-bytes 1 467838) (vectors 16 11446)
  (vector-slots 8 175135 12716) (floats 8 24 32) (intervals 56 361 17)
  (buffers 992 12))

bug#66161: cperl-mode: fontification after __END__

[Harald Jörg]

CPerl mode fontifies Text after __END__ (and also after a __DATA__
token) like Perl - and I guess that this is intentional, supporting two
use cases of such text:

 - The AutoSplit and SelfLoader modules (both available in the Perl
   core) compile Perl sources written after these tokens only on demand
   (when they're first called).  For sources using these modules,
   treating these texts as Perl code is useful.  However, these days
   both modules are rarely used in new code.

 - The POD (Perl's documentation format) tools ignore the tokens, so
   many authors put their documentation after an __END__ token to speed
   up compilation.

For all other uses of the tokens (e.g. as a delimiter for end-of-file
comments), the fontification of CPerl mode looks messed up.  So I agree
that finding a way to make these texts less "colorful" makes sense.

perl-mode treats text after these tokens as a "c-style comment".  This
is elegant, but I would not want to apply this unconditionally to
cperl-mode: comments are excluded from imenu indexing, which cperl-mode
performs for both subroutines and POD headings.

-- 
Cheers,
haj

bug#66161: cperl-mode: fontification after __END__

[Harald Jörg]

This has now been solved in the master branch by adding a new option
`cperl-fontify-trailer':  If the value is "perl-code" (the default),
then cperl-mode treats it as code.  If the value is "comment", then
cperl-mode treats text after __END__ (and text after __DATA__) as
comment.

Here are some popular modules from CPAN to illustrate the different use
cases for text after __END__.  In my opinion this justifies the
introduction of yet another option:

 - POD documentation after __END__ is seen in Moo (and many others):
   https://metacpan.org/dist/Moo/source/lib/Moo.pm

 - Perl code after __END__ is used in Tk:
   https://metacpan.org/dist/Tk/source/Tk.pm

 - Trailing comments are used in Pod::Simple:
   https://metacpan.org/dist/Pod-Simple/source/lib/Pod/Simple.pm

Therefore, I am closing this bug report.
-- 
Cheers,
haj