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Date: Thu, 10 Dec 2009 10:03:46 -0600
From: Anthony Liguori <aliguori@linux.vnet.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH 10/19] monitor: Convert do_info_name() to
	QObject
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To: Avi Kivity <avi@redhat.com>
Cc: qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>, Luiz Capitulino <lcapitulino@redhat.com>

Avi Kivity wrote:
> On 12/10/2009 02:56 PM, Anthony Liguori wrote:
>>
>> I'd prefer an empty dict.  I actually prefer that over null.
>>
>
> Depends.  Key not present suggests the feature is not implemented.  
> Value is null suggests the feature is not used.  Both key and value 
> present suggest the feature is in implemented and active.

What I suggested to Luiz was that all info commands return a 
dictionary.  The main reason was that for most commands, we can extend 
the commands in a compatible way by adding new fields to the dictionary.

My expectation is that there will be a lot of client code that does:

hpet_info = qmp.info_hpet()
if hpet_info.has_key('period'):
   period = hpet_info['period']
else:
   period = 100 # old qemu's has a fixed period of 100ns

So in keeping with this idiom, I think that checking 
name_info.has_key('name') is a more meaningful way to determine whether 
the virtual machine has been given a name vs comparing name_info['name'] 
== None.

-- 
Regards,

Anthony Liguori