bug#17174: 24.3; perl-mode highlight: unrecognized perl var $' starts a string

bug#17174: 24.3; perl-mode highlight: unrecognized perl var $' starts a string

[G.raud]

The bug is an old one, found in Emacs 22, 23 and 24 in Debian.

To test:

$ cat <<"EOF" >test.pl
#!/usr/bin/perl
$_ = 'truc'; /ru/;
print "$'\n"; # this is highlighted as expected
print $'; # this starts a string that continues to the next line
print "\n";
EOF
$ emacs24 -Q test.pl

The output of (report-bug-emacs) follows.

---

In GNU Emacs 24.3.1 (x86_64-pc-linux-gnu, GTK+ Version 3.8.6)
 of 2013-12-22 on brahms, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11204000
Configured using:
 `configure '--build' 'x86_64-linux-gnu' '--build' 'x86_64-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var/lib' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'
 '--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.3/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.3/site-lisp:/usr/share/emacs/site-lisp'
 '--with-crt-dir=/usr/lib/x86_64-linux-gnu' '--with-x=yes'
 '--with-x-toolkit=gtk3' '--with-toolkit-scroll-bars'
 'build_alias=x86_64-linux-gnu' 'CFLAGS=-g -O2 -fstack-protector
 --param=ssp-buffer-size=4 -Wformat -Werror=format-security -Wall'
 'LDFLAGS=-Wl,-z,relro' 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LANG: de_DE.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Major mode: Perl

Minor modes in effect:
  tooltip-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

Recent input:
M-x r e p o r t <tab> <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
user-error: Beginning of history; no preceding item
user-error: End of history; no default available
(New file)
Mark set
byte-code: End of buffer [2 times]

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message format-spec rfc822 mml easymenu
mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mail-utils
perl-mode ffap url-parse auth-source eieio byte-opt bytecomp
byte-compile cconv gnus-util mm-util mail-prsvr password-cache url-vars
time-date tooltip ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
lisp-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer loaddefs button faces cus-face macroexp files text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process dbusbind
dynamic-setting system-font-setting font-render-setting move-toolbar gtk
x-toolkit x multi-tty emacs)

-- 

bug#17174: 24.3; perl-mode highlight: unrecognized perl var $' starts a string

[Stefan Monnier]

> $ cat <<"EOF" >test.pl
> #!/usr/bin/perl
> $_ = 'truc'; /ru/;
> print "$'\n"; # this is highlighted as expected
> print $'; # this starts a string that continues to the next line
> print "\n";
> EOF
> $ emacs24 -Q test.pl

Thanks for the clear test case.  I installed the patch below in
emacs-24, which should fix it.


        Stefan


--- lisp/progmodes/perl-mode.el	2014-04-02 19:50:05 +0000
+++ lisp/progmodes/perl-mode.el	2014-04-03 00:37:11 +0000
@@ -250,7 +250,11 @@
       ;; Catch ${ so that ${var} doesn't screw up indentation.
       ;; This also catches $' to handle 'foo$', although it should really
       ;; check that it occurs inside a '..' string.
-      ("\\(\\$\\)[{']" (1 ". p"))
+      ("\\(\\$\\)[{']" (1 (unless (and (eq ?\' (char-after (match-end 1)))
+                                       (save-excursion
+                                         (not (nth 3 (syntax-ppss
+                                                      (match-beginning 0))))))
+                            (string-to-syntax ". p"))))
       ;; Handle funny names like $DB'stop.
       ("\\$ ?{?^?[_[:alpha:]][_[:alnum:]]*\\('\\)[_[:alpha:]]" (1 "_"))
       ;; format statements