Re: [PATCH v2 0/2] MR8555: windows.devices.enumeration: Reimplement DeviceInformationStatics::FindAllAsync and DeviceWatcher using the device query API.

[Rémi Bernon (＠rbernon)]

Rémi Bernon (@rbernon) commented about dlls/windows.devices.enumeration/main.c:
>  case DeviceWatcherStatus_Stopped: hr = E_ILLEGAL_METHOD_CALL; break;
>  case DeviceWatcherStatus_Stopping: hr = E_ILLEGAL_METHOD_CALL; break;
>  default: hr = E_ILLEGAL_METHOD_CALL;
> - case DeviceWatcherStatus_EnumerationCompleted:
> -
>    impl->status = DeviceWatcherStatus_Stopping;
> -
>    hr = async_action_create( (IUnknown *)iface, device_watcher_stop_async, &async );
> -
>    if (SUCCEEDED(hr)) IAsyncAction_Release( async );
> -
>    break;
> case DeviceWatcherStatus_Started:
>        impl->status = DeviceWatcherStatus_Stopping;
> -
>    /* an async start is in progress, let it handle stopped state change */
> -
>    if (impl->query)
> -
>        DevCloseObjectQuery( impl->query );

The state machine should guarantee that `impl->query` is set here. What about enforcing `DevCloseObjectQuery called && query == NULL` as an invariant everywhere, like this instead:

```suggestion:-1+0
        DevCloseObjectQuery( impl->query );
        impl->query = NULL;
```

And remove the corresponding `watcher->query = NULL` above on `DevQueryStateClosed`.