Re: [PATCH 06/29] bisect: libify `exit_if_skipped_commits` to `error_if_skipped*` and its dependents

From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: Miriam Rubio <mirucam@gmail.com>
Cc: git@vger.kernel.org, Pranit Bauva <pranit.bauva@gmail.com>,
	Christian Couder <chriscool@tuxfamily.org>,
	Tanushree Tumane <tanushreetumane@gmail.com>
Subject: Re: [PATCH 06/29] bisect: libify `exit_if_skipped_commits` to `error_if_skipped*` and its dependents
Date: Mon, 20 Jan 2020 22:57:40 +0100 (CET)	[thread overview]
Message-ID: <nycvar.QRO.7.76.6.2001202253450.46@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <20200120143800.900-7-mirucam@gmail.com>

Hi Miriam,

On Mon, 20 Jan 2020, Miriam Rubio wrote:

> From: Pranit Bauva <pranit.bauva@gmail.com>
>
> Since we want to get rid of git-bisect.sh it would be necessary to
> convert those exit() calls to return statements so that errors can be
> reported.
>
> Emulate try catch in C by converting `exit(<positive-value>)` to
> `return <negative-value>`. Follow POSIX conventions to return
> <negative-value> to indicate error.

Good.

> Modify `cmd_bisect_helper()` to handle these negative returns.
>
> Turn `exit()` to `return` calls in `exit_if_skipped_commits()` and rename
> the method to `error_if_skipped_commits()`.

I would remove these two sentences, as I deem it obvious from the
rationale above that this needs to be done, and the patch repeats it.

>
> Handle this return in dependant function `bisect_next_all()`.
>
> Mentored-by: Christian Couder <chriscool@tuxfamily.org>
> Mentored-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
> Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
> Signed-off-by: Tanushree Tumane <tanushreetumane@gmail.com>
> Signed-off-by: Miriam Rubio <mirucam@gmail.com>
> ---
>  bisect.c | 23 ++++++++++++++++-------
>  1 file changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/bisect.c b/bisect.c
> index 83cb5b3a98..2ac0463327 100644
> --- a/bisect.c
> +++ b/bisect.c
> @@ -661,11 +661,11 @@ static void bisect_common(struct rev_info *revs)
>  		mark_edges_uninteresting(revs, NULL, 0);
>  }
>
> -static void exit_if_skipped_commits(struct commit_list *tried,
> +static int error_if_skipped_commits(struct commit_list *tried,
>  				    const struct object_id *bad)
>  {
>  	if (!tried)
> -		return;
> +		return 0;
>
>  	printf("There are only 'skip'ped commits left to test.\n"
>  	       "The first %s commit could be any of:\n", term_bad);
> @@ -676,7 +676,13 @@ static void exit_if_skipped_commits(struct commit_list *tried,
>  	if (bad)
>  		printf("%s\n", oid_to_hex(bad));
>  	printf(_("We cannot bisect more!\n"));
> -	exit(2);
> +
> +	/*
> +	 * We don't want to clean the bisection state
> +	 * as we need to get back to where we started
> +	 * by using `git bisect reset`.
> +	 */
> +	return -2;

This comment is a good indicator that the constant `-2` here is a "magic"
number and it would most likely make sense to turn the return type from an
`int` into an `enum` instead.

>  }
>
>  static int is_expected_rev(const struct object_id *oid)
> @@ -949,7 +955,7 @@ int bisect_next_all(struct repository *r, const char *prefix, int no_checkout)
>  {
>  	struct rev_info revs;
>  	struct commit_list *tried;
> -	int reaches = 0, all = 0, nr, steps;
> +	int reaches = 0, all = 0, nr, steps, res;
>  	struct object_id *bisect_rev;
>  	char *steps_msg;
>
> @@ -972,8 +978,9 @@ int bisect_next_all(struct repository *r, const char *prefix, int no_checkout)
>  		 * We should exit here only if the "bad"
>  		 * commit is also a "skip" commit.
>  		 */
> -		exit_if_skipped_commits(tried, NULL);
> -
> +		res = error_if_skipped_commits(tried, NULL);
> +		if (res)
> +			exit(-res);

So we still `exit()` in `libgit.a`? I hoped for a more thorough
libification.

Besides, the `if (res)` probably wants to be an `if (res < 0)`, right?

Ciao,
Johannes

>  		printf(_("%s was both %s and %s\n"),
>  		       oid_to_hex(current_bad_oid),
>  		       term_good,
> @@ -990,7 +997,9 @@ int bisect_next_all(struct repository *r, const char *prefix, int no_checkout)
>  	bisect_rev = &revs.commits->item->object.oid;
>
>  	if (oideq(bisect_rev, current_bad_oid)) {
> -		exit_if_skipped_commits(tried, current_bad_oid);
> +		res = error_if_skipped_commits(tried, current_bad_oid);
> +		if (res)
> +			exit(-res);
>  		printf("%s is the first %s commit\n", oid_to_hex(bisect_rev),
>  			term_bad);
>  		show_diff_tree(r, prefix, revs.commits->item);
> --
> 2.21.1 (Apple Git-122.3)
>
>