Re: [Qemu-devel] [PATCH v6 05/12] qapi: Track location that created an implicit type

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> A future patch will enable deferred error detection in the
> various QAPISchema*.check() methods (rather than the current
> ad hoc parse checks).

What's "deferred" about them?

Perhaps simply: A future patch will move error checking into the various
QAPISchema*.check() methods.

>                        But that means the user can request
> a QAPI entity that will only fail validation after it has
> been initialized.

I'm not sure I get this sentence.

>                    Since all errors have to have an
> associated 'info' location, we need a location to be
> associated with all user-triggered implicit types.  The
> intuitive info to use is the location of the enclosing
> entity that caused the creation of the implicit type.

Yes.

> Note that we do not anticipate builtin types being used in
> an error message (as they are not part of the user's QAPI
> input, the user can't cause a semantic error in their
> behavior), so we exempt those types from requiring info,

Yes, no errors should be reported for built-in entities.

Sometimes, an error message for one entity wants to refer to some other
entity.  We'll have to take care not to blindly use info then.

>                                                          by
> setting a flag to track the completion of _def_predefineds().

Explaining the implementation here seems premature.

> No change to the generated code.
>
> RFC: I used a class-level static flag to track whether we expected
> 'info is None' when creating a QAPISchemaEntity.  This is gross,
> because the flag will only be set on the first QAPISchema() instance
> (it works because none of our client scripts ever instantiate more
> than one schema).  But the only other thing I could think of would
> be passing the QAPISchema instance into the constructor for each
> QAPISchemaEntity, which is a lot of churn.  Any better ideas on how
> best to do the assertion, or should I just drop it?
>
> Signed-off-by: Eric Blake <eblake@redhat.com>

I'd check in QAPISchema._def_entity().

Patch looks good otherwise.