bug#74307: 30.0.92; emacs-lisp font-locking word regexp

bug#74307: 30.0.92; emacs-lisp font-locking word regexp

[Roland Winkler]

Starting from emacs -Q, put the following into a buffer with
emacs-lisp-mode

  (setq foo "\\<foo\\>")

The part "foo\\" of the string "\\<foo\\>" will get
font-lock-variable-name-face, which looks odd.

I believe, this is due to a clause in lisp-mode.el that says

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

But this assumption is not always correct, in particular if ">" is
preceded by "\\", which happens when constructing regexps.

bug#74307: 30.0.92; emacs-lisp font-locking word regexp

[Eli Zaretskii]

> From: Roland Winkler <winkler@gnu.org>
> Date: Mon, 11 Nov 2024 00:28:34 -0600
> 
> Starting from emacs -Q, put the following into a buffer with
> emacs-lisp-mode
> 
>   (setq foo "\\<foo\\>")
> 
> The part "foo\\" of the string "\\<foo\\>" will get
> font-lock-variable-name-face, which looks odd.
> 
> I believe, this is due to a clause in lisp-mode.el that says
> 
>          ;; Words inside \\[], \\<>, \\{} or \\`' tend to be for
>          ;; `substitute-command-keys'.
> 
> But this assumption is not always correct, in particular if ">" is
> preceded by "\\", which happens when constructing regexps.

I believe you are saying that in

         (,(rx "\\\\" (or (seq "<" (group-n 1 lisp-mode-symbol) ">")
                          (seq "{" (group-n 1 lisp-mode-symbol) "}")))
          (1 font-lock-variable-name-face prepend))

we should use something like the below instead?

     (,(rx "\\\\" (or (seq "<" (group-n 1 lisp-mode-symbol) (not "\\\\") ">")
                      (seq "{" (group-n 1 lisp-mode-symbol) (not "\\\\") "}"))

And similarly for \\[] etc.?

bug#74307: 30.0.92; emacs-lisp font-locking word regexp

[Stefan Monnier via Bug reports for GNU Emacs, the Swiss army knife of text editors]

> I believe you are saying that in
>
>          (,(rx "\\\\" (or (seq "<" (group-n 1 lisp-mode-symbol) ">")
>                           (seq "{" (group-n 1 lisp-mode-symbol) "}")))
>           (1 font-lock-variable-name-face prepend))
>
> we should use something like the below instead?
>
>      (,(rx "\\\\" (or (seq "<" (group-n 1 lisp-mode-symbol) (not "\\\\") ">")
>                       (seq "{" (group-n 1 lisp-mode-symbol) (not "\\\\") "}"))
>
> And similarly for \\[] etc.?

Sounds good to me.


        Stefan

bug#74307: 30.0.92; emacs-lisp font-locking word regexp

[Roland Winkler]

On Thu, Nov 14 2024, Eli Zaretskii wrote:
> we should use something like the below instead?
>
>      (,(rx "\\\\" (or (seq "<" (group-n 1 lisp-mode-symbol) (not "\\\\") ">")
>                       (seq "{" (group-n 1 lisp-mode-symbol) (not "\\\\") "q}"))

Yes, thanks.  (This is my first real-world encounter with rx.  Otherwise
I would have proposed it myself.)

> And similarly for \\[] etc.?

I do not know in what context backslash-quoted right square brackets may
appear in regexps.  But certainly, they do not make sense in the context
of substitute-command-keys either.  So excluding here backslash-quoted
right square brackets is probably for the better, too.