Subject: Re: [PATCH v2 3/4] builtin/pack-objects.c: ensure included `--stdin-packs` exist

From: Taylor Blau <[email-masked]>
Date: Tue, 24 May 2022 17:33:56 -0400

On Tue, May 24, 2022 at 09:46:09PM +0200, Ævar Arnfjörð Bjarmason wrote:
>
> On Tue, May 24 2022, Taylor Blau wrote:
>
> > -	struct rev_info *revs = _data;
> > -	struct object_info oi = OBJECT_INFO_INIT;
> >  	off_t ofs;
> > -	enum object_type type;
> > +	enum object_type type = OBJ_NONE;
> >
> >  	display_progress(progress_state, ++nr_seen);
> >
> > @@ -3215,20 +3213,25 @@ static int add_object_entry_from_pack(const struct object_id *oid,
> >  	if (!want_object_in_pack(oid, 0, &p, &ofs))
> >  		return 0;
> >
> > -	oi.typep = &type;
> > -	if (packed_object_info(the_repository, p, ofs, &oi) < 0)
> > -		die(_("could not get type of object %s in pack %s"),
> > -		    oid_to_hex(oid), p->pack_name);
> > -	else if (type == OBJ_COMMIT) {
> > -		/*
> > -		 * commits in included packs are used as starting points for the
> > -		 * subsequent revision walk
> > -		 */
> > -		add_pending_oid(revs, NULL, oid, 0);
> > +	if (p) {
> > +		struct rev_info *revs = _data;
> > +		struct object_info oi = OBJECT_INFO_INIT;
> > +
> > +		oi.typep = &type;
> > +		if (packed_object_info(the_repository, p, ofs, &oi) < 0) {
> > +			die(_("could not get type of object %s in pack %s"),
> > +			    oid_to_hex(oid), p->pack_name);
> > +		} else if (type == OBJ_COMMIT) {
> > +			/*
> > +			 * commits in included packs are used as starting points for the
> > +			 * subsequent revision walk
> > +			 */
> > +			add_pending_oid(revs, NULL, oid, 0);
> > +		}
> > +
> > +		stdin_packs_found_nr++;
> >  	}
> >
> > -	stdin_packs_found_nr++;
> > -
> >  	create_object_entry(oid, type, 0, 0, 0, p, ofs);
>
> Not rhetorical, since I have no idea: Is the behavior change here to
> make create_object_entry with type=OBJ_NONE desired? I.e. do we actually
> want to create object entries for OBJ_NONE?

This is intentional. OBJ_NONE tells create_object_entry() "we don't know
the type of this object yet", and then `check_object()` (which does the
bulk of the work in the "Counting objects" phase) goes through and fills
in any missing type information.

The caller in `builtin/pack-objects.c::read_object_list_from_stdin()` is
a good example of this (all of the objects created this way start out
with OBJ_NONE).

> If that is the case I for one would find this a bit easier to follow
> like this, even if it has some minor duplication, i.e. the intent is
> clearer:
>
> 	diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
> 	index ffeaecd1d84..a447f6d5164 100644
> 	--- a/builtin/pack-objects.c
> 	+++ b/builtin/pack-objects.c
> 	@@ -3202,7 +3202,6 @@ static int add_object_entry_from_pack(const struct object_id *oid,
> 	 				      void *_data)
> 	 {
> 	 	off_t ofs;
> 	-	enum object_type type = OBJ_NONE;
>
> 	 	display_progress(progress_state, ++nr_seen);
>
> 	@@ -3216,6 +3215,7 @@ static int add_object_entry_from_pack(const struct object_id *oid,
> 	 	if (p) {
> 	 		struct rev_info *revs = _data;
> 	 		struct object_info oi = OBJECT_INFO_INIT;
> 	+		enum object_type type;
>
> 	 		oi.typep = &type;
> 	 		if (packed_object_info(the_repository, p, ofs, &oi) < 0) {
> 	@@ -3230,9 +3230,11 @@ static int add_object_entry_from_pack(const struct object_id *oid,
> 	 		}
>
> 	 		stdin_packs_found_nr++;
> 	-	}
>
> 	-	create_object_entry(oid, type, 0, 0, 0, p, ofs);
> 	+		create_object_entry(oid, type, 0, 0, 0, p, ofs);
> 	+	} else  {
> 	+		create_object_entry(oid, OBJ_NONE, 0, 0, 0, p, ofs);
> 	+	}
>
> 	 	return 0;
> 	 }
>
> Or the same with adding "type = OBJ_NONE" to the "else" branch, leaving
> the initial "type" uninitialized"?

I'd be fine with that (and don't really have a very strong opinion
either way). Let's see if anybody else has thoughts about it, and then
I'm happy to change it in a subsequent version.

Thanks,
Taylor