Re: [Qemu-devel] [RFC] Defining firmware (OVMF, et al) metadata format & file

[Laszlo Ersek <lersek@redhat.com>]

On 04/06/18 20:10, Eric Blake wrote:
> On 04/06/2018 12:28 PM, Laszlo Ersek wrote:
>
>> I've created an RFC-level "qapi/firmware.json" schema file, based on
>> this discussion. It "builds", and the generated documentation looks
>> acceptable, superficially speaking.
>>
>> Before I post "qapi/firmware.json" for getting comments, I'd like to
>> write JSON text that (a) describes firmware that I use, and (b)
>> conforms to the schema. IOW, I'd like to validate whether the schema
>> is good enough for describing at least such firmware that I know.
>>
>> Is there a tool that generates example JSON objects from a given
>> schema?
>
> I know the QMP shell (scripts/qmp/qmp-shell) lets you enter commands
> with a lot less typing than full JSON, and has a mode where it will
> then echo the full JSON command it constructed from what you typed. To
> be able to quickly validate examples, it may be sufficient to
> temporarily add a new QMP command 'check-firmware':
>
> { 'command': 'check-firmware', 'boxed': true, 'data': 'Firmware' }
>
> assuming 'Firmware' is your top-level 'struct' in the QAPI file, then
> implement a trivial:
>
> qmp_check_firmware(Firmware *obj, Error **errp) {
>     return 0;
> }
>
> so that you can then run QMP shell, and type:
>
> check-firmware arg1=foo arg2=bar ...
>
> which will then generate the corresponding JSON, then either
> successfully do nothing (what you typed validated, AND you have the
> JSON output printed), or print an error (what you typed failed QAPI
> validation, perhaps because it had an unrecognized key, was missing a
> required key, used a wrong type, etc).
>
>> I vaguely recall there used to be one. Otherwise, writing the
>> examples manually looks arduous (and I wouldn't know how to verify
>> them against the schema).
>
> Similarly, if you generate a command the produces a 'Firmware' as the
> return value, then you can populate the generated C struct (since you
> did manage to run the QAPI generator over your new file, you should be
> able to look at the C struct it generated), then output that over QMP
> to show the counterpart JSON that matches the struct as populated.
>

The top level structure is complex / nested, but that doesn't appear to
be an issue. According to the script,

# key=value pairs also support Python or JSON object literal subset notations,
# without spaces. Dictionaries/objects {} are supported as are arrays [].
#
#    example-command arg-name1={'key':'value','obj'={'prop':"value"}}
#
# Both JSON and Python formatting should work, including both styles of
# string literal quotes. Both paradigms of literal values should work,
# including null/true/false for JSON and None/True/False for Python.

This looks awesome, because it should let me provide messy nested input
(which I'll obviously compose in my $EDITOR and then paste it), and then
the QMP shell will both validate and pretty print that. I'm going to try
this.

Thank you, Eric!
Laszlo