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

Patrick Steinhardt [off-list ref] writes:

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.

 	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.

 	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.

On Fri, Jan 08, 2021 at 03:50:00PM -0800, Junio C Hamano wrote:

Patrick Steinhardt [off-list ref] writes:

[snip]

quoted

 	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;
	}

Agreed, that is easier to read. Thanks!

Patrick