[v2] grep: improve errors for unmatched ( and )

Commit Message

Ahelenia Ziemiańska March 23, 2024, 1:18 p.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.

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.

Link: https://bugs.debian.org/1051205
Signed-off-by: Ahelenia Ziemiańska <[e-mail]>
---
On Fri, Mar 22, 2024 at 09:41:40AM -0700, Junio C Hamano wrote:
> Ahelenia Ziemiańska <[e-mail]> writes:
> > 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.
False. -- turns all subsequent parameters into arguments, and if
there is no -e, the first argument is the pattern, and all the
subsequent ones are paths. This is normal [git] grep behaviour.

> Just keep "-e '('" in the
> description and drop the double-dash there.
Disagree. This is one of the two methodologies I've devised to work
around this in the past, and it's one of the two methodologies that
work.

All else applied.

 grep.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Junio C Hamano March 23, 2024, 6:06 p.m. UTC | #1

Ahelenia Ziemiańska <[e-mail]> writes:

> 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.
>
> 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.
>
> Link: https://bugs.debian.org/1051205
> Signed-off-by: Ahelenia Ziemiańska <[e-mail]>
> ---
> On Fri, Mar 22, 2024 at 09:41:40AM -0700, Junio C Hamano wrote:
>> Ahelenia Ziemiańska <[e-mail]> writes:
>> > 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.
> False. -- turns all subsequent parameters into arguments, and if
> there is no -e, the first argument is the pattern, and all the
> subsequent ones are paths. This is normal [git] grep behaviour.

Ah, thanks.  

I forgot that "git grep" was a oddball that allows revs come after
"--" in some cases.  As long as the user understands this may not
work for other commands, it is OK.  "-e" is the only officially
supported way (which is why I mentioned it in the review comments I
gave you here), so guiding users in that direction would be a better
idea anyway, though.

Thanks.

> 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);

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);