Re: [libvirt] [Xen-devel] [PATCH 5/5] Add a test suite for libxl option generator

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

On Mon, Jun 02, 2014 at 01:53:46PM +0100, Ian Campbell wrote:
> 
> On Fri, 2014-05-30 at 18:24 +0100, Daniel P. Berrange wrote:
> > +    if (STRNEQ(expectargv, (char *)actualargv)) {
> > +        virtTestDifference(stderr, expectargv, (char *)actualargv);
> > +        goto cleanup;
> > +    }
> 
> Since you are using libxl_domain_config_gen_json you can control the
> pretty printing, but if you were to use the libxl_domain_config_to_json
> you might have problems if the library was to do something slightly
> different e.g. with whitespace.
> 
> In 4.5 we will have libxl_*_from_json and (I think) libxl_*_compare, so
> you could read in the template and compare it with the generated struct.
> That doesn't help you now of course.
> 
> Also in 4.5 the json will omit fields which are set to the their
> explicit default value. libxl_*_from_json will still do the right thing,
> but it'd be another annoyance for you here I think.
> 
> Lastly, when we add new fields to the API they will start showing up in
> the json (modulo the omission of defaults discussed above).

Hmm, that's a v good point.

> Other than having a template per libxl version (yuck) I don't have any
> particularly smart suggestions except for to aim long
> term for:
>   libxl_domain_config_init(..., &template)
>   libxl_domain_config_from_json(..., &template, "{ json json json ....")
> 
>   libxl_domain_config_init(..., &xml)
>   virtLibxlFromXML(..., &xml, "<domain>....")
> 
>   libxl_domain_config_compare(&template, &xml)
> 
> which will likely handle all of those corner cases, except perhaps the
> case where libvirt is using new fields on new versions of libxl etc. I
> suppose that would be handled by specific unit tests for >= and <
> versions of libxl separately?

I think that perhaps I should just add a general JSON "DOM" comparison
function in libvirt - no need for it to be libxl specific, as it might
be useful for libvirt JSON usage elsewhere.

Regards,
Daniel
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