Re: [PATCH v2 2/4] fetch: refactor `s_update_ref` to use common exit path

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 8, 2021, 23:50 UTC
Message-ID: <xmqqim87gf9z.fsf@gitster.c.googlers.com>
In-Reply-To: <718a8bf5d7a0ed92c3004991a42419279ff38253.1610107599.git.ps@pks.im>

Patrick Steinhardt <ps@pks.im> writes:

Show 22 quoted lines

> @@ -598,30 +598,33 @@ static int s_update_ref(const char *action,
>  	msg = xstrfmt("%s: %s", rla, action);
>  
>  	transaction = ref_transaction_begin(&err);
> -	if (!transaction ||
> -	    ref_transaction_update(transaction, ref->name,
> -				   &ref->new_oid,
> -				   check_old ? &ref->old_oid : NULL,
> -				   0, msg, &err))
> -		goto fail;
> +	if (!transaction) {
> +		ret = STORE_REF_ERROR_OTHER;
> +		goto out;
> +	}
> +
> +	ret = ref_transaction_update(transaction, ref->name, &ref->new_oid,
> +				     check_old ? &ref->old_oid : NULL,
> +				     0, msg, &err);
> +	if (ret) {
> +		ret = STORE_REF_ERROR_OTHER;
> +		goto out;
> +	}

The above certainly got cleaner thanks to Christian's suggestion, but I wonder why

	transaction = ref_transaction_begin(&err);
	if (!transaction ||
	    ref_transaction_update(transaction, ref->name,
				   &ref->new_oid,
				   check_old ? &ref->old_oid : NULL,
				   0, msg, &err)) {
		ret = STORE_REF_ERROR_OTHER;
		goto out;
	}

shouldn't be sufficient.

Show 11 quoted lines

>  	ret = ref_transaction_commit(transaction, &err);
>  	if (ret) {
> -		df_conflict = (ret == TRANSACTION_NAME_CONFLICT);
> -		goto fail;
> +		ret = (ret == TRANSACTION_NAME_CONFLICT) ? STORE_REF_ERROR_DF_CONFLICT
> +							 : STORE_REF_ERROR_OTHER;
> +		goto out;
>  	}
> 
> +out:
>  	ref_transaction_free(transaction);

It is a bit funny to see a goto that jumps to the label without having anything else in between, but we know we will be adding more code just before the "out:" label, so it is a good preliminary preparation.

I think a variant that is much easier to follow would be to write like this instead:

	switch (ref_transaction_commit(transaction, &err)) {
        case 0: /* happy */
		break;
	case TRANSACTION_NAME_CONFLICT:
		ret = STORE_REF_ERROR_DF_CONFLICT;
		goto out;
	default:
		ret = STORE_REF_ERROR_OTHER;
		goto out;
	}

> +	if (ret)
> +		error("%s", err.buf);

OK.

Show 14 quoted lines

>  	strbuf_release(&err);
>  	free(msg);
> -	return 0;
> -fail:
> -	ref_transaction_free(transaction);
> -	error("%s", err.buf);
> -	strbuf_release(&err);
> -	free(msg);
> -	return df_conflict ? STORE_REF_ERROR_DF_CONFLICT
> -			   : STORE_REF_ERROR_OTHER;
> +	return ret;
>  }
>  
>  static int refcol_width = 10;

THanks.