bug#23266: 25.0.92; GNUmakefile mode incorrect syntax highlighting

bug#23266: 25.0.92; GNUmakefile mode incorrect syntax highlighting

[Dima Kogan]

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Hi. I'm running an emacs built from the emacs-25 branch on 2016/04/05
(a05fb21). I'm seeing Makefiles incorrectly rendered at times. Example.
I load the following Makefile:

===================================
XXX :=						\
$(DIR)/aaa/bbb					\
$(DIR)/aaa/bbb					\
$(DIR)/aaa/bbb					\
$(DIR)/aaa/bbb					\
$(DIR)/aaa/bbb					\
$(DIR)/aaa/bbb					\
$(DIR)/aaa/bbb					\
$(DIR)/aaa/bbb					\
$(DIR)/aaa/bbb
===================================

Things look correct here. In particular all the DIR are rendered with
font-lock-variable-name-face

I then kill (with C-k) any of the DIR lines. Two of the DIR around the
line being killed then lose the font-lock-variable-name-face. The buffer
needs to be reverted to get proper highlighting back. I'm attaching
screenshots (emacs -Q -nw) before and after the kill.

Thanks



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bug#23266: 25.0.92; GNUmakefile mode incorrect syntax highlighting

[Andreas Schwab]

Dima Kogan <dima@secretsauce.net> writes:

> I then kill (with C-k) any of the DIR lines. Two of the DIR around the
> line being killed then lose the font-lock-variable-name-face. The buffer
> needs to be reverted to get proper highlighting back.

Does M-o M-o also restore proper highlighting?

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

bug#23266: 25.0.92; GNUmakefile mode incorrect syntax highlighting

[Anders Lindgren]

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Hi!

I think it's the following font-lock keyword that is broken:

    ("[^$]\\$[({]\\([-a-zA-Z0-9_.]+\\|[@%<?^+*][FD]?\\)"
      (1 font-lock-variable-name-face prepend))

The regexp match constructs like $(NAME). However, in an attempt not to
match $$(NAME), it tries to match any other character besides $ before
$(NAME). When $(NAME) is at the beginning of a line, at the beginning of
the search, this fails.

The reason why the buffer originally is colored correctly is that the [^$]
match the newline of the previous line. However, after an edit, font-lock
only highlights the edited parts. When the search resumes on a line
starting with $(NAME), the regexp no longer match.

You can verify this in Font-Lock Studio (
https://github.com/Lindydancer/font-lock-studio) by first single-stepping
(SPC) the rule in the whole buffer, then mark a single line and step only
that line, using `font-lock-studio' and `font-lock-studio-region',
respectively.

This can be fixed in a number of ways:

 * Replace "[^$]" with "\\(^\\|[^$]\\)", which mean to match the beginning
of a line or any non-$ character.

 * Implement the search in a function that would search for the regex
(except the "[^$]" part) plus code to check that it's not preceded by a "$".

 * Extend the region that should be highlighted to include all lines that
end with the "\" character. This can be done by adding a mode-specific
function to `font-lock-extend-region-functions'.

Note that there seems to be six rules in Makefile mode using this pattern,
I guess all of them needs to be fixes.

    -- Anders Lindgren

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bug#23266: 25.0.92; GNUmakefile mode incorrect syntax highlighting

[Lars Ingebrigtsen]

Anders Lindgren <andlind@gmail.com> writes:

> This can be fixed in a number of ways:
>
>  * Replace "[^$]" with "\\(^\\|[^$]\\)", which mean to match the beginning of a
> line or any non-$ character.

Thanks; I did this in Emacs 28, and it seems to fix the issue.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no