I have changed the comment. Thanks.
On Tue, Jul 8, 2014 at 4:48 AM, Michael Haggerty <mhagger@alum.mit.edu> wrote:
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> I'm in my next attempt to get through your patch series. Sorry for the
> long hiatus.
>
> Patches 1-19 look OK aside from a minor typo that I just reported.
>
> See below for a comment on this patch.
>
> On 06/20/2014 04:43 PM, Ronnie Sahlberg wrote:
>> Do basic error checking in ref_transaction_create() and make it return
>> non-zero on error. Update all callers to check the result of
>> ref_transaction_create(). There are currently no conditions in _create that
>> will return error but there will be in the future. Add an err argument that
>> will be updated on failure.
>>
>> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
>> Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
>> ---
>> builtin/update-ref.c | 4 +++-
>> refs.c | 18 +++++++++++------
>> refs.h | 55 +++++++++++++++++++++++++++++++++++++++++++++-------
>> 3 files changed, 63 insertions(+), 14 deletions(-)
>>
>> diff --git a/builtin/update-ref.c b/builtin/update-ref.c
>> index 3067b11..41121fa 100644
>> --- a/builtin/update-ref.c
>> +++ b/builtin/update-ref.c
>> @@ -226,7 +226,9 @@ static const char *parse_cmd_create(struct strbuf *input, const char *next)
>> if (*next != line_termination)
>> die("create %s: extra input: %s", refname, next);
>>
>> - ref_transaction_create(transaction, refname, new_sha1, update_flags);
>> + if (ref_transaction_create(transaction, refname, new_sha1,
>> + update_flags, &err))
>> + die("%s", err.buf);
>>
>> update_flags = 0;
>> free(refname);
>> diff --git a/refs.c b/refs.c
>> index 3f05e88..c49f1c6 100644
>> --- a/refs.c
>> +++ b/refs.c
>> @@ -3449,18 +3449,24 @@ int ref_transaction_update(struct ref_transaction *transaction,
>> return 0;
>> }
>>
>> -void ref_transaction_create(struct ref_transaction *transaction,
>> - const char *refname,
>> - const unsigned char *new_sha1,
>> - int flags)
>> +int ref_transaction_create(struct ref_transaction *transaction,
>> + const char *refname,
>> + const unsigned char *new_sha1,
>> + int flags,
>> + struct strbuf *err)
>> {
>> - struct ref_update *update = add_update(transaction, refname);
>> + struct ref_update *update;
>> +
>> + if (!new_sha1 || is_null_sha1(new_sha1))
>> + die("BUG: create ref with null new_sha1");
>> +
>> + update = add_update(transaction, refname);
>>
>> - assert(!is_null_sha1(new_sha1));
>> hashcpy(update->new_sha1, new_sha1);
>> hashclr(update->old_sha1);
>> update->flags = flags;
>> update->have_old = 1;
>> + return 0;
>> }
>>
>> void ref_transaction_delete(struct ref_transaction *transaction,
>> diff --git a/refs.h b/refs.h
>> index c5376ce..33b4383 100644
>> --- a/refs.h
>> +++ b/refs.h
>> @@ -10,6 +10,45 @@ struct ref_lock {
>> int force_write;
>> };
>>
>> +/*
>> + * A ref_transaction represents a collection of ref updates
>> + * that should succeed or fail together.
>> + *
>> + * Calling sequence
>> + * ----------------
>> + * - Allocate and initialize a `struct ref_transaction` by calling
>> + * `ref_transaction_begin()`.
>> + *
>> + * - List intended ref updates by calling functions like
>> + * `ref_transaction_update()` and `ref_transaction_create()`.
>> + *
>> + * - Call `ref_transaction_commit()` to execute the transaction.
>> + * If this succeeds, the ref updates will have taken place and
>> + * the transaction cannot be rolled back.
>> + *
>> + * - At any time call `ref_transaction_free()` to discard the
>> + * transaction and free associated resources. In particular,
>> + * this rolls back the transaction if it has not been
>> + * successfully committed.
>> + *
>> + * Error handling
>> + * --------------
>> + *
>> + * On error, transaction functions append a message about what
>> + * went wrong to the 'err' argument. The message mentions what
>> + * ref was being updated (if any) when the error occurred so it
>> + * can be passed to 'die' or 'error' as-is.
>> + *
>> + * The message is appended to err without first clearing err.
>> + * This allows the caller to prepare preamble text to the generated
>> + * error message:
>> + *
>> + * strbuf_addf(&err, "Error while doing foo-bar: ");
>> + * if (ref_transaction_update(..., &err)) {
>> + * ret = error("%s", err.buf);
>> + * goto cleanup;
>> + * }
>> + */
>
> I don't have a problem with the API, but I think the idiom suggested in
> the comment above is a bit silly. Surely one would do the following
> instead:
>
> if (ref_transaction_update(..., &err)) {
> ret = error("Error while doing foo-bar: %s", err.buf);
> goto cleanup;
> }
>
> I think it would also be helpful to document whether the error string
> that is appended to the strbuf is terminated with a LF.
>
>> [...]
>
> Michael
>
> --
> Michael Haggerty
> mhagger@alum.mit.edu
>Ronnie Sahlberg <sahlberg@google.com>