Re: [PATCH v2 08/18] python: backport 'make require() preserve async-ness'

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Sep 03, 2025 at 01:11:14AM -0400, John Snow wrote:
> This is not strictly needed functionality-wise, but doing this allows
> sphinx to see which decorated methods are async. Without this, sphinx
> misses the "async" classifier on generated docs, which ... for an async
> library, isn't great.
> 
> It does make an already gnarly function even gnarlier, though.
> 
> So, what's going on here?
> 
> A synchronous function (like require() before this patch) can return a
> coroutine that can be awaited on, for example:
> 
>   def some_func():
>       return asyncio.task(asyncio.sleep(5))
> 
>   async def some_async_func():
>       await some_func()
> 
> However, this function is not considered to be an "async" function in
> the eyes of the abstract syntax tree. Specifically,
> some_func.__code__.co_flags will not be set with CO_COROUTINE.
> 
> The interpreter uses this flag to know if it's legal to use "await" from
> within the body of the function. Since this function is just wrapping
> another function, it doesn't matter much for the decorator, but sphinx
> uses the stdlib inspect.iscoroutinefunction() to determine when to add
> the "async" prefix in generated output. This function uses the presence
> of CO_COROUTINE.
> 
> So, in order to preserve the "async" flag for docs, the require()
> decorator needs to differentiate based on whether it is decorating a
> sync or async function and use a different wrapping mechanism
> accordingly.
> 
> Phew.
> 
> Signed-off-by: John Snow <jsnow@redhat.com>
> cherry picked from commit 40aa9699d619849f528032aa456dd061a4afa957
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  python/qemu/qmp/protocol.py | 53 ++++++++++++++++++++++---------------
>  1 file changed, 32 insertions(+), 21 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


With regards,
Daniel
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