Subject: Re: [PATCH v8 10/44] refs.c: change ref_transaction_update() to do error checking and return status

From: Jonathan Nieder <[email-masked]>
Date: Thu, 15 May 2014 12:34:46 -0700

Ronnie Sahlberg wrote:

> Update ref_transaction_update() do some basic error checking and return
> non-zero on error. Update all callers to check ref_transaction_update() for
> error. There are currently no conditions in _update that will return error but
> there will be in the future.

Probably worth passing a 'struct strbuf *err' argument.  Then callers
can do

		die("%s", err.buf);

and the error message can say which ref and whether we were trying to
create a ref, or delete one, or whatever.

> --- a/builtin/update-ref.c
> +++ b/builtin/update-ref.c
> @@ -197,8 +197,9 @@ static const char *parse_cmd_update(struct strbuf *input, const char *next)
>  	if (*next != line_termination)
>  		die("update %s: extra input: %s", refname, next);
>  
> -	ref_transaction_update(transaction, refname, new_sha1, old_sha1,
> -			       update_flags, have_old);
> +	if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
> +				   update_flags, have_old))
> +		die("update %s: failed", refname);

This could say

		die("update %s: %s", refname, err.buf);

to give context about which command it was trying to execute.

[...]
> @@ -286,8 +287,9 @@ static const char *parse_cmd_verify(struct strbuf *input, const char *next)
>  	if (*next != line_termination)
>  		die("verify %s: extra input: %s", refname, next);
>  
> -	ref_transaction_update(transaction, refname, new_sha1, old_sha1,
> -			       update_flags, have_old);
> +	if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
> +				   update_flags, have_old))
> +		die("failed transaction update for %s", refname);

And this could say

		die("verify %s: %s", refname, err.buf);

[...]
> --- a/refs.h
> +++ b/refs.h
> @@ -242,12 +242,15 @@ void ref_transaction_rollback(struct ref_transaction *transaction);
>   * be deleted.  If have_old is true, then old_sha1 holds the value
>   * that the reference should have had before the update, or zeros if
>   * it must not have existed beforehand.
> + * Function returns 0 on success and non-zero on failure. A failure to update
> + * means that the transaction as a whole has failed and will need to be
> + * rolled back.
> + */

Thanks for this documentation.