Subject: bug#76759: closed (Re: bug#76759: [PATCH] 31.0.50; makefile-mode: incorrectly highlights make-instructions as make targets)

From: [email-masked] (GNU bug Tracking System)
Date: Mon, 10 Mar 2025 02:17:03 +0000

Your bug report

#76759: [PATCH] 31.0.50; makefile-mode: incorrectly highlights make-instructions as make targets

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
76759: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=76759
GNU Bug Tracking System
Contact [email-masked] with problems

Subject: Re: bug#76759: [PATCH] 31.0.50; makefile-mode: incorrectly highlights make-instructions as make targets
From: Stefan Monnier <[email-masked]>
To: Jostein Kjønigsen <[email-masked]>
Cc: "Dr. Arne Babenhauserheide" <[email-masked]>, "Ergus via Emacs development discussions." <[email-masked]>, Mauro Aranda <[email-masked]>, [email-masked]
Date: Sun, 09 Mar 2025 22:08:04 -0400
List-Id: <debbugs-submit.debbugs.gnu.org>

> Any news on this one?

Looks OK, tho I think it's a bit more strict than necessary: the TABs we
need to avoid can be only at the beginning of the line, so not inside
the $(...).

So it's only one of the [^...] that needs the \t.

Here's what I did:

- Start from the current monster:

    "^\\(\\(?:\\$\\(?:[({]\\(?:\\$\\(?:[({]\\(?:\\$\\(?:[^({]\\|.[^\n$#})]+?[})]\\)\\|[^\n$#)}]\\)+?[})]\\|[^({]\\)\\|[^\n$#)}]\\)+?[})]\\|[^({]\\)\\|[^\n$#:=]\\)+?\\)\\(:\\)\\(?:[ \t]*$\\|[^=\n]\\(?:[^#\n]*?;[ \t]*\\(.+\\)\\)?\\)"

- Change the `\\(?:[^({]\\|.` to `\\(?:[^({]\\|[({]` because I think
  the `.` was just an optimization.  And since the two alternatives are
  now mutually exclusive, swap them:

    \\(?:[^({]\\|.[^\n$#})]+?[})]\\)

=>

    \\(?:[({][^\n$#})]+?[})]\\|[^({]\\)

- Now the regexp has become:

    "^\\(\\(?:\\$\\(?:[({]\\(?:\\$\\(?:[({]\\(?:\\$\\(?:[({][^\n$#})]+?[})]\\|[^({]\\)\\|[^\n$#)}]\\)+?[})]\\|[^({]\\)\\|[^\n$#)}]\\)+?[})]\\|[^({]\\)\\|[^\n$#:=]\\)+?\\)\\(:\\)\\(?:[ \t]*$\\|[^=\n]\\(?:[^#\n]*?;[ \t]*\\(.+\\)\\)?\\)"

- Make the nested construction explicit, so it's a bit more manageable:

    (letrec ((elems-re
              (lambda (n &optional outer)
                (if (< n 1)
                     "[^\n$#})]+?"
                  (concat "\\(?:\\$\\(?:"
                          "[({]" (funcall elems-re (- n 1)) "[})]"
                          "\\|[^({]\\)"
                          "\\|[^\n$#" (if outer ":=" ")}") "]\\)+?")))))
      (concat
       ;; Allow for two nested levels $(v1:$(v2:$(v3:a=b)=c)=d)
       "^\\(" (funcall elems-re 3 'outer)
       "\\)\\(:\\)\\(?:[ \t]*$\\|[^=\n]\\(?:[^#\n]*?;[ \t]*\\(.+\\)\\)?\\)"))

- Disallow TABs in the outer case by replacing ":=" with "\t:=" (that's
  one of the TABs you added in your version of the patch).

This is still not quite right, since AFAIK TABs are allowed to appear
outside of $(...) as long as they're not at BOL, but I think it's better
than what we've had so far (and the regexp still has several other
limitations anyway).

Pushed to `master`.

        Stefan

Subject: [PATCH] 31.0.50; makefile-mode: incorrectly highlights make-instructions as make targets
From: Jostein Kjønigsen <[email-masked]>
To: [email-masked]
Cc: "Ergus via Emacs development discussions." <[email-masked]>
Date: Wed, 5 Mar 2025 10:32:39 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

Hey everyone.

I found a bug in makefile-mode fontification.

Currently shell-commands/make-instructions within a target may get fontified as make-targets if they contain a : (colon) sign.

Consider the following make-target:

------- Makefile ------

run-docker: build-docker
	docker run -p 8080:8080 imagename

--------------------------

This defined a make-target called "run-docker" which depends on "build-docker", which runs the command "docker run -p 8080:8080 imagename".

In the current code, since the command contains a ":" the whole text up to that point ("docker run -p 8080") gets fontified as a make-target, even though it's clearly not declared at the beginning of the line.

Based on my digging, this seems to be due to the matching criteria defined in makefile-dependency-regex.

A common pattern used in this regex is "[^\n$#]" (with slight variations), which (from how I read regexps) aims to match anything which is not a lineshift, a $-sign or a #-sign.

"Anything" in this case would then also include whitespace, which IMO is the source of the bug.

I've tried changing this part of the statement in parts of the regex to "[^\n\s$#]", like in the attached patch. Ie also exclude leading whitespace. From what I've tested, it does not seem to have any adverse effects, although I may not have tested all areas affected by this change.

Feel free to test the suggested changes, and let me know if they can be improved in any way.

￼
—
Kind Regards
Jostein Kjønigsen

In GNU Emacs 31.0.50 (build 19, aarch64-apple-darwin24.3.0, NS
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Repository branch: master
Windowing system distributor 'Apple', version 10.3.2575
System Description:  macOS 15.3.1

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