Re: [Qemu-devel] [PATCH v5 12/46] qapi: Track location that created an implicit type

[Eric Blake <eblake@redhat.com>]

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On 09/28/2015 06:56 AM, Markus Armbruster wrote:
> Eric Blake <eblake@redhat.com> writes:
> 
>> A future patch will enable error detection in the various
>> QapiSchema check() methods.  But since all errors have to
>> have an associated 'info' location, we need a location to
>> be associated with all implicit types.  Easiest is to reuse
>> the location of the enclosing entity that includes the
>> dictionary defining the implicit type.
>>
>> While at it, we were always passing None as the location of
>> array types, making that parameter useless; sharing the
>> location (if any) of the underlying element type makes sense.
> 
> The parameter is useless only because all array types are implicit.
> Once we change that, it won't be anymore.

I guess it depends whether I pass in the existing info when creating the
array or determine the info when resolving the string name of the array
element during check() (it will ultimately be the same info either way,
it's just a question of which approach looks cleaner for getting the
information set).


>> @@ -917,6 +917,7 @@ class QAPISchemaArrayType(QAPISchemaType):
>>      def check(self, schema):
>>          self.element_type = schema.lookup_type(self._element_type_name)
>>          assert self.element_type
>> +        self._info = self.element_type._info
>>
>>      def json_type(self):
>>          return 'array'
> 
> Implicit array type's info is the element type's info.  Okay.
> 
>> @@ -928,6 +929,7 @@ class QAPISchemaArrayType(QAPISchemaType):
>>  class QAPISchemaObjectType(QAPISchemaType):
>>      def __init__(self, name, info, base, local_members, variants):
>>          QAPISchemaType.__init__(self, name, info)
>> +        assert info or name == ':empty'
> 
> I think what we really want to assert is "we got info unless this is a
> built-in entity", in QAPISchemaEntity.__init__().

To do that, arrays would have to pass info in to __init__() rather than
deferring to check() as I did above.

> 
> Built-in entities are exactly the types defined by
> QAPISchema._def_predefineds(), currently the built-in types and
> ':empty'.

I'm still wondering how best to test that, but agree that hoisting the
assert into QAPISchemaEntity instead of just in QAPISchemaObjectType
would be nice.  Maybe some sort of boolean switch, initially off, then
turned on after _def_predefineds() is called, and assuming that no types
other than predefineds are initialized prior to that point.

> 
> Missing: implicit enum types' info.

I'll add it; should be the info of the containing union type that caused
the implicit enum.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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