How about highlighting captured groups in regex?

[Dominique Pellé]

Hi

Vim now highlights matching text when
typing a Ex command like :%s/foobar/
I like it. But I wish that it would use
a different color for the regex captured group(s).

For example, if I do :%s/foo\(bar\)/
I would like "bar" (the captured group) to
be highlighted with a different color than foo
in matching text, so it's easier to visually see
that my regexp matches and what \1 is
when I do :%s/foo\(bar\)/\1/. In this example
the regexp and captured group are obvious
of course, so a different color may not seem
useful. But it becomes more useful when the
the regex is more complex.

There are 10 possibly regexp groups. Having 10
different colors might be overkill (not sure).
The same color for any group may good enough,
or perhaps alternative colors for \1 \2 \3...?

I wonder whether other vim users would also
find it useful.

Regards
Dominique

[Ingo Karkat]

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I like this idea. It can help by visualizing a complex pattern (while
it's being composed), and it could also be (mis?)used to have multiple
patterns highlighted with different colors in parallel, e.g.
/\(foo\)\|\(bar\)/ would show "foo" in color 1 and "bar" in color 2.
There's definitely demand for that, currently implemented by plugins
(such as my own Mark.vim,
http://www.vim.org/scripts/script.php?script_id=2666) via matchadd().

Regarding the mechanics, I think the biggest challenge lies in the
association of capture group number to highlight group. As your
questions show, this mostly isn't static, but would depend on each
particular pattern. Of course, one could use an off-band mechanism
like separate :hi link Search1 ... | hi link Search2 ... Ex commands
to reconfigure the colors, but that would be cumbersome.

I would suggest to decouple the capture groups from the highlighting,
and instead extend the non-capturing group syntax (\%(...\)) to
optionally supply a color number: \%1(...\) uses Search1, \%2(...\)
uses Search2, and so on. (This is modeled after \%23l, \%23c, ..., and
would not break backwards compatibility.) This allows an in-band
group-to-color mapping, with the downside that captured groups would
have to be explicitly wrapped in a numbered non-capturing group; the
example from above would become a more verbose
/\%1(\(foo\)\)\|\%2(\(bar\)\)/; the benefit would be that another
capture group can be easily added that also uses color 1, or 2, or no
special color at all.

- -- regards, ingo

- --
-- Ingo Karkat -- /^-- /^-- /^-- /^-- /^-- http://ingo-karkat.de/ --
-- https://www.vim.org/account/profile.php?user_id=9713 --
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[Andy Wokula]

Am 07.10.2019 um 13:51 schrieb Dominique Pell??:
> Hi
>
> Vim now highlights matching text when

> typing an Ex command like :%s/foobar/

What about nesting / overlapping group matches (?):
/foo\(ba\(baz\)r\)

can be several levels deep.

--
Andy

[Dominique Pellé]

Andy Wokula wrote

The outer group in your example is \1 and the

inner group is \(baz\) is \1.  Highlighting of inner group

should shadow highlighting of outer groups I would

say in the common portion of the matched text.

So matching text when searching for /foo\(ba\(baz\)r\)

could look like this for example if:
* Search group is yellow

* \1 is light brown

* \2 is darker brown

  xxfoobabazrxx

But multiple colors for \1, \2 (etc) is maybe overkill.

Personally I'd be happy enough with a single color for all

captured groups, i.e.:

  xxfoobabazrxx

Regards

Dominique

[Andy Wokula]

> xxfoobabazr__xx

> But multiple colors for \1, \2 (etc) is maybe overkill.
> Personally I'd be happy enough with a single color for all
> captured groups, i.e.:

> xxfoobabazr__xx
> Regards
> Dominique

What about rainbow-highlighting of parens `\(', `\)'?
Ie instead of highlighting the text, just highlight
the grouping parens.

And then, `\1', `\2' ... using the same colors.

I'd prefer that, also because weird colors will not hide
my regexp text then.

--
Andy