GNU bug report logs - #41522
26.3; Narrowing can prevent syntax propertization

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Ikumi Keita <ikumi <at> ikumi.que.jp>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.3; Narrowing can prevent syntax propertization
Date: Mon, 25 May 2020 17:42:09 +0900

[Message part 1 (text/plain, inline)]

When syntax propertization occurs inside narrowed area of a buffer,
the outside area sometimes doesn't get syntax propertization even after
the narrowing is removed.

[How to reproduce]
1. Save the attached sample file as /tmp/sample.sh
2. emacs -Q -geometry 80x25 /tmp/sample.sh
3. Type C-u C-n C-e to go to the end of the (visible) fourth line.
4. Type C-x C-e as the comment there instructs.
5. Then the face of here-doc bleeds over the "EOF" token and continues
   to the end of the buffer.
   Expected result is that the here-doc face ends at "EOF" and the rest
   of the buffer is fontified with various suitable faces.

[Analysis]
In the above example, `narrow-to-region' restricts the buffer into the
last three lines of Local Variables section where syntax propertization
is not yet done. There, `syntax-ppss' triggers syntax propertization and
set `syntax-propertize--done' to (point-max). But actually that
`syntax-ppss' didn't syntax-properize outside the narrowing so it didn't
give the suitable `syntax-table' property to the newline following the
"EOF". Since `syntax-propertize--done' tells emacs that all portion of
the buffer has been propertized already, emacs does not give the
suitable `syntax-table' property to the newline following the "EOF" even
after `widen'. Thus the fontification of here-doc continues beyond "EOF".

In a similar way, if a lisp function goes to the point where syntax
propertization has not yet took place, makes narrowing and calls some
syntax-aware function which sets `syntax-propertize--done' to a value
inside the narrowing, a large portion of the buffer can be left without
suitable `syntax-table' property. This can lead to incorrect result
for not only font-lock but also syntax-aware functions such as
`forward-comment'.

Best regards,
Ikumi Keita

In GNU Emacs 26.3 (build 1, x86_64-unknown-freebsd12.0, GTK+ Version 3.24.9)
 of 2019-08-29 built on freebsd.vmware
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
Recent messages:
Indentation variables are now local.
Indentation setup for shell type sh
 [2 times]
Mark set
Saving file /home/keita/scr/sample.sh...
Wrote /home/keita/scr/sample.sh
Setting up indent for shell type sh
Indentation variables are now local.
Indentation setup for shell type sh


Configured using:
 'configure --with-canna --with-canna-includes=/usr/local/canna/include
--with-canna-libraries=/usr/local/canna/lib --without-xim
--disable-largefile --with-sound=yes --with-file-notification=yes
CFLAGS=-O3'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS GSETTINGS GLIB NOTIFY ACL GNUTLS
LIBXML2 FREETYPE XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM THREADS
LCMS2

Important settings:
  value of $EMACSLOADPATH: /home/keita/elisp:
  value of $LANG: ja_JP.eucJP
  locale-coding-system: japanese-iso-8bit-unix

Major mode: Info

Minor modes in effect:
  TeX-PDF-mode: t
  global-magit-file-mode: t
  diff-auto-refine-mode: t
  magit-auto-revert-mode: t
  global-git-commit-mode: t
  async-bytecomp-package-mode: t
  shell-dirtrack-mode: t
  tooltip-mode: t
  global-eldoc-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
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
~/elisp/preview hides /usr/local/share/emacs/site-lisp/auctex/preview
~/elisp/reftex-parse hides /usr/local/share/emacs/26.3/lisp/textmodes/reftex-parse
/home/keita/.emacs.d/elpa/soap-client-3.1.5/soap-client hides /usr/local/share/emacs/26.3/lisp/net/soap-client
/home/keita/.emacs.d/elpa/soap-client-3.1.5/soap-inspect hides /usr/local/share/emacs/26.3/lisp/net/soap-inspect

Features:
(ibuf-ext ibuffer ibuffer-loaddefs shadow mh-mime mh-identity
mh-tool-bar mh-letter mh-show goto-addr gnus-cite gnus-art mm-uu mml2015
gnus-sum gnus-group gnus-undo gnus-start gnus-cloud nnimap nnmail
mail-source utf7 netrc nnoo gnus-spec gnus-int gnus-win gnus-range gnus
nnheader wid-edit mh-xface mh-utils mh-comp mh-scan mh-gnus mm-view
mml-smime smime dig mh-e mh-compat mh-buffers mh-loaddefs emacsbug
sendmail sh-script smie executable perl-mode magit-extras vc-git pp
preview prv-emacs reftex-dcr reftex-auc reftex reftex-loaddefs
reftex-vars tex-bar tex-buf toolbar-x noutline outline font-latex latex
latex-flymake flymake-proc flymake warnings tex-ispell tex-style tex
dbus tex-mode compile latexenc misearch multi-isearch eieio-opt speedbar
sb-image ezimage dframe find-func cl-print thingatpt help-fns radix-tree
bug-reference edmacro kmacro magit-submodule magit-obsolete magit-blame
magit-stash magit-reflog magit-bisect magit-push magit-pull magit-fetch
magit-clone magit-remote magit-commit magit-sequence magit-notes
magit-worktree magit-tag magit-merge magit-branch magit-reset
magit-files magit-refs magit-status magit magit-repos magit-apply
magit-wip magit-log which-func imenu magit-diff smerge-mode diff-mode
magit-core magit-autorevert autorevert filenotify magit-margin
magit-transient magit-process magit-mode git-commit transient magit-git
magit-section magit-utils crm log-edit easy-mmode message dired
dired-loaddefs format-spec rfc822 mml mml-sec gnus-util rmail
rmail-loaddefs mm-decode mm-bodies mm-encode mailabbrev mail-utils
gmm-utils mailheader pcvs-util add-log with-editor async-bytecomp async
shell pcomplete comint ansi-color ring server subr-x dash skeleton
cl-extra help-mode parse-time ucs-normalize json map epa derived epg
url-http tls gnutls url-auth mail-parse rfc2231 rfc2047 rfc2045 mm-util
ietf-drums mail-prsvr url-gw nsm rmc puny jka-compr twittering-mode
advice url url-proxy url-privacy url-expand url-methods url-history
url-cookie url-domsuf url-util mailcap xml elec-pair preview-latex
auto-loads tex-site canna-im finder-inf info package easymenu epg-config
url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache url-vars seq byte-opt gv bytecomp
byte-compile cconv cl-loaddefs cl-lib time-date mule-util japan-util
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 menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame 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 minibuffer cl-preloaded nadvice loaddefs
button faces cus-face macroexp files text-properties overlay sha1 md5
base64 format env code-pages mule custom widget hashtable-print-readable
backquote threads dbusbind kqueue lcms2 dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 813972 71846)
 (symbols 48 48314 42)
 (miscs 40 4992 2861)
 (strings 32 186223 9232)
 (string-bytes 1 5882079)
 (vectors 16 83667)
 (vector-slots 8 2273246 58558)
 (floats 8 330 584)
 (intervals 56 12890 4833)
 (buffers 992 41))

[sample.sh (text/x-shellscript, attachment)]

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