Re: [pcre-dev] bug#60690: [PATCH v2] grep: correctly identif…

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Author: Paul Eggert
To: Ævar Arnfjörð Bjarmason, Carlo Marcelo Arenas Belón
CC: demerphq, pcre-dev, 60690, gitster, git
Subject: Re: [pcre-dev] bug#60690: [PATCH v2] grep: correctly identify utf-8 characters with \{b, w} in -P
On 1/9/23 03:35, Ævar Arnfjörð Bjarmason wrote:

> You almost never want "everything Unicode considers a digit", and if you
> do using e.g. \p{Nd} instead of \d would be better in terms of
> expressing your intent.

For GNU grep, PCRE2_UCP is needed because of examples like what Gro-Tsen
and Karl Petterssen supplied. If there's some diagreement about how \d
should behave with UTF-8 data the GNU grep hackers should let the Perl
community decide that; that is, GNU grep can simply follow PCRE2's lead.
But GNU grep does need PCRE2_UCP for \b etc.

>     $ diff <(git -P grep -P '\d+') <(git -P grep -P '(*UCP)\d')
>     53360a53361,53362
>     > git-gui/po/ja.po:"- 第1行: 何をしたか、を1行で要約。\n"
>     > git-gui/po/ja.po:"- 第2行: 空白\n"

Although I don't speak Japanese I have dealt with quite a bit of
Japanese text in a previous job, and personally I would prefer \d to
match those two lines as they do contain digits. So to me this
particular case is not a good argument that git grep should not match
those lines.

Of course other people might prefer differently, and there are cases
where I want to match only ASCII digits. I've learned in the past to use
[0-9] for that. I hope PCRE2 never changes [0-9] to match anything but
ASCII digits when searching UTF-8 text.