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

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

On Tue, May 24 2022, Taylor Blau wrote:

> 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.

Ah, I didn't know that.

> 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.

FWIW I think you should place a particularly low value on my suggestion
of this.

I.e. the last thing we should do is probably to optimize the code to be
read by someone who hadn't spent even 10 minutes finding out such
obvious major code-flow details, i.e. me not knowing about how OBJ_NONE
was used in this case....

So it's probably all fine as-is, but p erhaps others will think it's
good or whatever...