synax highlighting anomaly

[Dave McCooey]

Hello,

There is a problem with syntax highlighting in "rc" files (e.g. _vimrc).

I am using the following commands to highlight tabs:

:hi Tab ctermbg=235

autocmd BufWinEnter * syntax match Tab /\t/ containedin=ALL

This works as expected in file types like .c, .html, .js, and .java.

In "rc" files, however, a tab is not highlighted when it is preceded

by a string consisting entirely of decimal digits (e.g. 55, 123, 9000).

Adding spaces between the number string and the tab does not

change the behavior - the tab is still not highlighted.

The ftplugin files are the default ones included in the distribution.

This problem is seen with vim version 8.2 (included patches 1-4372)

on Cygwin, and also with version 8.2 (included patches 1-2072) on Linux.

I have version 7.3 running on a Mac that does not have the problem.

Best regards,

Dave McCooey

[Christian Brabandt]

Can you please provide a reproducible example? Also, it is not clear
what kind of an rc file you are using (and there are various rc
filetypes available, like muttrc and fetchmailrc, so I need something
reproducible).

I tried with something silly like foobar.rc and do not see the problem
in there using:

vim --clean -c ':hi Tab ctermbg=235' --cmd 'autocmd BufWinEnter * syntax
match Tab /\t/ containedin=ALL' foobar.rc


Best,
Christian
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[Dave McCooey]

Hi Christian,

The file with the problem is _vimrc itself, which is how I noticed it.

Here is a line from my _vimrc that shows the problem:

:hi Tab ctermbg=235\t" Grey19 = 0x303030

The \t is really a single tab character.

My assumption that _vimrc is an "rc" file appears to be wrong,

because if I copy _vimrc to xxx.rc, then xxx.rc does not have the problem.

Best regards,

Dave McCooey

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[Christian Brabandt]

On So, 25 Sep 2022, Dave McCooey wrote:

> Hi Christian,
>
> The file with the problem is _vimrc itself, which is how I noticed it.
>
> Here is a line from my _vimrc that shows the problem:
>
> :hi Tab ctermbg=235\t" Grey19 = 0x303030
>
> The \t is really a single tab character.
>
> My assumption that _vimrc is an "rc" file appears to be wrong,
> because if I copy _vimrc to xxx.rc, then xxx.rc does not have the problem.

I have been digging around the vim syntax file a bit. At some point, the
vimNumber syntax definition added the 'skipwhite' argument to it, which
basically prevents that the whitespace after it can be matched by other
syntax rules.

In your case, I would change the BufWinEnter autocommand to a matchadd()
function call like this:

au BufWinEnter *.vim call matchadd('Tab', '\t')

Then it should be working again.

Thanks,
Chris
--
Wer sich frei entfalten will, muß viele Ratschläge in den Wind
schlagen können.
-- Werner Mitsch

[Dave McCooey]

On Mon, Sep 26, 2022 at 8:38 AM Christian Brabandt <cbl...@256bit.org> wrote:

On So, 25 Sep 2022, Dave McCooey wrote:

> Hi Christian,
>
> The file with the problem is _vimrc itself, which is how I noticed it.
>
> Here is a line from my _vimrc that shows the problem:
>
> :hi Tab ctermbg=235\t" Grey19 = 0x303030
>
> The \t is really a single tab character.
>
> My assumption that _vimrc is an "rc" file appears to be wrong,
> because if I copy _vimrc to xxx.rc, then xxx.rc does not have the problem.

I have been digging around the vim syntax file a bit. At some point, the
vimNumber syntax definition added the 'skipwhite' argument to it, which
basically prevents that the whitespace after it can be matched by other
syntax rules.

In your case, I would change the BufWinEnter autocommand to a matchadd()
function call like this:

au BufWinEnter *.vim call matchadd('Tab', '\t')

Then it should be working again.

Thanks for diagnosing the problem and for the work-around.

I had looked at matchadd() but was unsure about whether

clearmatches() needs to be called when leaving a window.

If I don't call it, then when I enter and leave a window repeatedly,

do the matches accumulate with repeated calls to matchadd()?

Best regards

Dave McCooey