Re: [PATCH] grep: improve errors for unmatched ( and )

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 22, 2024, 16:41 UTC
Message-ID: <xmqq34si2p8b.fsf@gitster.g>
In-Reply-To: <petpdy3bs6wpfd3ilrg6xrjsbj5y7ql4geps6y22ozdqw7vi4k@tarta.nabijaczleweli.xyz>

Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz> writes:

> Imagine you want to grep for (. Easy:

Please have a blank line before and

>   $ git grep '('
>   fatal: unmatched parenthesis

after a displayed text like this one (this applies to a few more paragraphs in the proposed log message).

> uhoh. This is plainly wrong. Unless you know specifically that
> (a) git grep has expression groups and that
> (b) the only way to work around them is by doing -- '(' or -e '('

I do not think "--" (end of options and beginning of pathspec) marker would work for that purpose, UNLESS you are talking about a file whose name is an open parenthesis. Just keep "-e '('" in the description and drop the double-dash there.

Show 5 quoted lines

> Similarly,
>   $ git grep ')'
>   fatal: incomplete pattern expression: )
> is somehow worse. ")" is a complete regular expression pattern.
> Of course, the error wants to say "group" here.

Nice problem description so far.

> These now return

Phrase it more like "Make them return" ...

>   $ ./git grep '('
>   fatal: unmatched ( for expression group
>   $ ./git grep ')'
>   fatal: incomplete pattern expression group: )

> which hopefully are clearer in indicating that it's not the expression
> that's wrong (since no pattern had been parsed at all), but rather that
> it's been misconstrued as a grouping operator.

Nicely done.

Show 28 quoted lines

> Link: https://bugs.debian.org/1051205
> Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
> ---
>  grep.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/grep.c b/grep.c
> index 5f23d1a..ac34bfe 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -621,7 +621,7 @@ static struct grep_expr *compile_pattern_atom(struct grep_pat **list)
>  		*list = p->next;
>  		x = compile_pattern_or(list);
>  		if (!*list || (*list)->token != GREP_CLOSE_PAREN)
> -			die("unmatched parenthesis");
> +			die("unmatched ( for expression group");
>  		*list = (*list)->next;
>  		return x;
>  	default:
> @@ -792,7 +792,7 @@ void compile_grep_patterns(struct grep_opt *opt)
>  	if (p)
>  		opt->pattern_expression = compile_pattern_expr(&p);
>  	if (p)
> -		die("incomplete pattern expression: %s", p->pattern);
> +		die("incomplete pattern expression group: %s", p->pattern);
>  
>  	if (opt->no_body_match && opt->pattern_expression)
>  		opt->pattern_expression = grep_not_expr(opt->pattern_expression);

Thanks.  The changes to these two messages look good.