Re: [PATCH 00/19] rust: QObject and QAPI bindings

[Paolo Bonzini <pbonzini@redhat.com>]

On 12/9/25 07:01, Markus Armbruster wrote:
> Markus Armbruster <armbru@redhat.com> writes:
> 
>> I applied, ran make, and it didn't create qapi-types.rs and
>> test-qapi-types.rs for me.  What am I missing?
> 
> Looks like I have to run with -B qapi.backend.QAPIRsBackend.
> 
> -B is meant for out-of-tree backends.  Commit dde279925c9 explains:
> 
>      qapi: pluggable backend code generators
>      
>      The 'qapi.backend.QAPIBackend' class defines an API contract for code
>      generators. The current generator is put into a new class
>      'qapi.backend.QAPICBackend' and made to be the default impl.
>      
>      A custom generator can be requested using the '-k' arg which takes a
>      fully qualified python class name
>      
>         qapi-gen.py -B the.python.module.QAPIMyBackend
>      
>      This allows out of tree code to use the QAPI generator infrastructure
>      to create new language bindings for QAPI schemas. This has the caveat
>      that the QAPI generator APIs are not guaranteed stable, so consumers
>      of this feature may have to update their code to be compatible with
>      future QEMU releases.
> 
> Using it for the in-tree Rust backend is fine for a prototype.
> Mentioning it in a commit message or the cover letter would've saved me
> some digging.

Well, it wasn't intentional - right now it does this:

test_qapi_rs_files = custom_target('QAPI Rust',
   output: 'test-qapi-types.rs',
   input: [ files(meson.project_source_root() + 
'/tests/qapi-schema/qapi-schema-test.json') ],
   command: [ qapi_gen, '-o', meson.current_build_dir(), '-b', 
'@INPUT0@', '-B', 'qapi.backend.QAPIRsBackend', '-p', 'test-' ],
   depend_files: [ qapi_inputs, qapi_gen_depends ])

so "make rust/tests/test-qapi-types.rs" will work, and so will "make" if 
you have --enable-rust.

Let us know what you'd prefer and we'll switch.  Alternatively, 
retconning -B's meaning so that it applies to Rust will work too. :)

Paolo