Re: [Qemu-devel] [PATCH] qmp-shell: fix pretty printing of JSON responses

["Daniel P. Berrange" <berrange@redhat.com>]

On Mon, Feb 22, 2016 at 03:02:03PM -0700, Eric Blake wrote:
> On 02/22/2016 10:02 AM, Daniel P. Berrange wrote:
> > Pretty printing of JSON responses is important to be able
> > to understand large responses from query commands in
> > particular, eg
> > 
> > (QEMU) query-chardev
> > {   u'return': [   {   u'filename': u'vc',
> >                        u'frontend-open': False,
> >                        u'label': u'parallel0'},
> >                    {   u'filename': u'vc',
> >                        u'frontend-open': True,
> >                        u'label': u'serial0'},
> >                    {   u'filename': u'unix:/tmp/qemp,server',
> >                        u'frontend-open': True,
> >                        u'label': u'compat_monitor0'}]}
> > 
> > Unfortunately this was broken during the addition of
> > the verbose flag in
> > 
> >   commit 1ceca07e48ead0dd2e41576c81d40e6a91cafefd
> >   Author: John Snow <jsnow@redhat.com>
> >   Date:   Wed Apr 29 15:14:04 2015 -0400
> > 
> >     scripts: qmp-shell: Add verbose flag
> > 
> > This is because that change turned the python data
> > structure into a formatted JSON string before the
> > pretty print was given it. So we're just pretty
> > printing a string, which is a no-op.
> > 
> > This fixes pretty printing of the command responses
> > and as an added benefit it will also pretty print
> > command arguments in verbose mode
> > 
> > (QEMU) object-add qom-type=secret id=sec0 props={"data":"123456"}
> > {   'arguments': {   'id': 'sec0',
> >                      'props': {   u'data': u'123456'},
> > 		     'qom-type': 'secret'},
> > 		     'execute': 'object-add'}
> > 		 {   u'return': {   }}
> 
> That's an odd mix of regular and Unicode strings.  Any ideas why it is
> happening?  But the patch is a strict improvement, so:

It is todo with the way qmp-shell parses the command line. The qom-type
and id arguments it just parses directly, but the last props argument
it gets by using json.loads() which returns unicode strings.

I realized we can avoid this issue and improve output style by not
pretty printing a python data struture, and instead telling the json
formatter to pretty print its output. So I've sent a v2 that does that

Regards,
Daniel
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