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grep: improve errors for unmatched ( and )

Message ID petpdy3bs6wpfd3ilrg6xrjsbj5y7ql4geps6y22ozdqw7vi4k@tarta.nabijaczleweli.xyz (mailing list archive)
State Superseded
Headers show
Series grep: improve errors for unmatched ( and ) | expand

Commit Message

Ahelenia Ziemiańska March 22, 2024, 8:34 a.m. UTC
Imagine you want to grep for (. Easy:
  $ git grep '('
  fatal: unmatched parenthesis
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 '('

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.
In this case it's also not "incomplete", it's unmatched.
But whatever.

These now 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.

Link: https://bugs.debian.org/1051205
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
---
 grep.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Junio C Hamano March 22, 2024, 4:41 p.m. UTC | #1
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.

> 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.

> 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.
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Patch

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);