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Date: Fri, 2 Oct 2009 15:32:16 -0300
From: Luiz Capitulino <lcapitulino@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v1 00/14]: Initial QObject conversion
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: aliguori@us.ibm.com, qemu-devel@nongnu.org, avi@redhat.com

On Fri, 02 Oct 2009 17:36:13 +0200
Gerd Hoffmann <kraxel@redhat.com> wrote:

>    Hi,
> >
> >> So maybe they shouldn't be named MonitorError in the first place?
> >
> >   What do you suggest?
> >
> >   Hm.. This could be QError, meaning that it's also a QObject,
> > so that we can put it in dicts, lists, etc.
> 
> Makes sense to me.
> 
> Attaching the pretty-print callback to the error struct not to the 
> monitor command is a good move too.  Makes it easier to reuse these 
> functions.
> 
> Hmm, maybe it would be even better to link the pretty-print functions to 
> error codes?

 Yes, I'll try that.

> >> Why user_error is needed in the first place btw?  To maintain
> >> backward-compatible error message formating?
> >
> >   Yes and to do pretty printing too.
> >
> >   For example:
> >
> > qemu_error("Device \"%s\" not found.  Try -device '?' for a list.\n",
> >             driver);
> >
> >   Makes sense for humans, but for QMP it would probably look like:
> >
> > { "error": { "code": 1234,
> >               "desc": "device not found",
> >               "data": { "name": "foobar-device" } } }
> 
> You could have a generic function which makes a message like this:
> 
>    'device not found: name=foobar-device'
> 
> out of the QError.  Not too bad.  You'll loose the '-device ?' hint though.
> 
> I think it is reasonable to make the pretty-print callback optional and 
> use the generic function in case it isn't present.  So you have 
> something working by default and can override it of the message isn't 
> userfriendly or backward-compatible enougth.

 Yeah, it's a good idea.

> >   So, when QMP is disabled that function will be called to print the error
> > for humans. When QMP is enabled this is never called and the protocol
> > emission code will use QError to emit something like the { "error" }
> > dict above.
> 
> Thanks for the explanation.

 Thanks for the feedback!