Re: [PATCH 02/18] fuse: Allow exporting BDSs via FUSE

[Kevin Wolf]

Am 20.12.2019 um 13:48 hat Markus Armbruster geschrieben:
> Kevin Wolf <address@hidden> writes:
> 
> > Am 20.12.2019 um 11:48 hat Max Reitz geschrieben:
> >> So if we kept writable and growable in the common base, then the schema
> >> would give no information about what exports actually support them.
> >> 
> >> On one hand, I don’t know whether it’s important to have this
> >> information in a static form, or whether it’s sufficient to learn at
> >> runtime.
> >> 
> >> On the other, I don’t know whether it’s important to have those fields
> >> in the base or not.  Would it make a difference on the wire?
> >
> > Not for the command itself, so I think we're free to change it later. It
> > might make a difference for introspection, though, not sure. Markus?
> 
> QAPI schema introspection is designed to hide the difference between
> local members and base members.  You can move members to or from a base
> type freely without affecting introspection.  Even if that creates or
> deletes the base type.

Good, that's helpful. So I can split the nbd-server-add argument type
into a base that is reused as a union branch and the rest without
potentially breaking anything.

I suppose moving a field between a union base and all variants does
still result in different introspection even though the accepted inputs
are the same. Is this kind of movement still allowed unconditionally or
should we be more careful with something like this?

Kevin