bug#68318: 30.0.50; Fontification of \{m\} and \{m,n\} in a regexp

bug#68318: 30.0.50; Fontification of \{m\} and \{m,n\} in a regexp

[Arash Esbati]

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Hi all,

to reproduce, start 'emacs -Q' and paste the following lines into
scratch:

(re-search-forward "a\\{7\\}")

(re-search-forward "a\\{7,\\}")

(re-search-forward "a\\{,7\\}")

For me, it looks like this:

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Hitting 'C-u C-x =' on the first 7 and the backslashes says:

  There are text properties here:
    face                 (font-lock-variable-name-face font-lock-string-face)
    fontified            t

On the next two forms, I get:

  There are text properties here:
    face                 font-lock-string-face
    fontified            t

Is this difference on purpose?

Best, Arash

In GNU Emacs 30.0.50 (build 1, aarch64-apple-darwin23.2.0, NS
 appkit-2487.30 Version 14.2.1 (Build 23C71)) of 2024-01-07 built on
 MacMutant.fritz.box
Repository revision: f866c85ac4e32df8061b285b6b44b15346994f3d
Repository branch: master
Windowing system distributor 'Apple', version 10.3.2487
System Description:  macOS 14.2.1

Configured using:
 'configure --with-ns --without-pop --without-mailutils --with-threads
 --with-modules --with-native-compilation --without-compress-install
 'CFLAGS=-O2 -g0 -pipe'
 'CPPFLAGS=-I/opt/homebrew/Cellar/gcc/13.2.0/include
 -I/opt/homebrew/Cellar/libgccjit/13.2.0/include
 -I/opt/homebrew/Cellar/gmp/6.3.0/include'
 'LDFLAGS=-L/opt/homebrew/Cellar/gcc/13.2.0/lib/gcc/current
 -L/opt/homebrew/Cellar/gmp/6.3.0/lib''

Configured features:
ACL GLIB GMP GNUTLS JSON LCMS2 LIBXML2 MODULES NATIVE_COMP NOTIFY KQUEUE
NS PDUMPER PNG RSVG SQLITE3 THREADS TOOLKIT_SCROLL_BARS TREE_SITTER WEBP
XIM ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

bug#68318: 30.0.50; Fontification of \{m\} and \{m,n\} in a regexp

[Andreas Schwab]

See lisp-el-font-lock-keywords-2 in lisp-mode.el:

         ;; Words inside \\[], \\<>, \\{} or \\`' tend to be for
         ;; `substitute-command-keys'.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

bug#68318: 30.0.50; Fontification of \{m\} and \{m,n\} in a regexp

[Arash Esbati]

Andreas Schwab <schwab@linux-m68k.org> writes:

> See lisp-el-font-lock-keywords-2 in lisp-mode.el:
>
>          ;; Words inside \\[], \\<>, \\{} or \\`' tend to be for
>          ;; `substitute-command-keys'.

Thanks for the pointer.  I'm not familiar with the code, but IIUC, the
lines 499-500 are relevant, where the condense is:

  (rx "\\\\" (seq "{" (group-n 1 lisp-mode-symbol) "}"))

which returns:

  "\\\\\\\\{\\(?1:\\(?:\\w\\|\\s_\\|\\\\.\\)+\\)}"

Since we're talking about \\{\\} and not \\{}, I wonder if some
variation like:

  "\\\\\\\\{\\(?1:\\(?:\\w\\|\\s_\\|\\\\.\\)*?[^\\]\\)}"

would fix this issue?  Not sure if it does TRT reg. the "\\\\." part.

Best, Arash