Re: [Qemu-devel] [PATCH v3 3/6] qmp: qmp_qom_list_properties(): ignore empty string options

[Markus Armbruster]

Igor Mammedov <address@hidden> writes:

> Current QAPI semantics return empty "" string in case string property
> value hasn't been set (i.e. NULL). Do not show initial value in this
> case in "qom-list-properties" command output to reduce clutter.
>
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
>  qmp.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/qmp.c b/qmp.c
> index 8415541..463c7d4 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -41,6 +41,7 @@
>  #include "qom/object_interfaces.h"
>  #include "hw/mem/memory-device.h"
>  #include "hw/acpi/acpi_dev_interface.h"
> +#include "qapi/qmp/qstring.h"
>  
>  NameInfo *qmp_query_name(Error **errp)
>  {
> @@ -596,7 +597,16 @@ ObjectPropertyInfoList *qmp_qom_list_properties(const 
> char *typename,
>          if (obj) {
>              info->q_default =
>                  object_property_get_qobject(obj, info->name, NULL);
> -            info->has_q_default = !!info->q_default;
> +            if (info->q_default) {
> +               if (qobject_type(info->q_default) == QTYPE_QSTRING) {
> +                   QString *value = qobject_to(QString, info->q_default);
> +                   if (!strcmp(qstring_get_str(value), "")) {
> +                       qobject_unref(info->q_default);
> +                       info->q_default = NULL;
> +                   }
> +               }
> +               info->has_q_default = !!info->q_default;
> +            }
>          }
>  
>          entry = g_malloc0(sizeof(*entry));

The commit message suggests we omit @default when a string-valued
property is null.  We omit it when it's "", too.

Makes me wonder whether we should omit other "default defaults", too,
such as integer zero.  After all, what's so special about strings?

I'm not sure omitting any default defaults is a good idea.  But then I'm
not yet sure @default is a good idea.