Re: [PATCH v3 12/16] python/machine.py: Add _qmp access shim

[Philippe Mathieu-Daudé]

On Sat, Jun 20, 2020 at 10:14 AM Philippe Mathieu-Daudé
<philmd@redhat.com> wrote:
>
> On 6/4/20 10:22 PM, John Snow wrote:
> > Like many other Optional[] types, it's not always a given that this
> > object will be set. Wrap it in a type-shim that raises a meaningful
> > error and will always return a concrete type.
> >
> > Signed-off-by: John Snow <jsnow@redhat.com>
> > ---
> >  python/qemu/machine.py | 12 +++++++++---
> >  1 file changed, 9 insertions(+), 3 deletions(-)
> >
> > diff --git a/python/qemu/machine.py b/python/qemu/machine.py
> > index d8289936816..a451f9000d6 100644
> > --- a/python/qemu/machine.py
> > +++ b/python/qemu/machine.py
> > @@ -118,7 +118,7 @@ def __init__(self, binary, args=None, wrapper=None, 
> > name=None,
> >          self._events = []
> >          self._iolog = None
> >          self._qmp_set = True   # Enable QMP monitor by default.
> > -        self._qmp = None
> > +        self._qmp_connection: Optional[qmp.QEMUMonitorProtocol] = None
> >          self._qemu_full_args = None
> >          self._temp_dir = None
> >          self._launched = False
> > @@ -285,7 +285,7 @@ def _pre_launch(self):
> >              if self._remove_monitor_sockfile:
> >                  assert isinstance(self._monitor_address, str)
> >                  self._remove_files.append(self._monitor_address)
> > -            self._qmp = qmp.QEMUMonitorProtocol(
> > +            self._qmp_connection = qmp.QEMUMonitorProtocol(
> >                  self._monitor_address,
> >                  server=True,
> >                  nickname=self._name
> > @@ -455,7 +455,13 @@ def set_qmp_monitor(self, enabled=True):
> >              self._qmp_set = True
> >          else:
> >              self._qmp_set = False
> > -            self._qmp = None
> > +            self._qmp_connection = None
> > +
> > +    @property
> > +    def _qmp(self) -> qmp.QEMUMonitorProtocol:
> > +        if self._qmp_connection is None:
> > +            raise QEMUMachineError("Attempt to access QMP with no 
> > connection")
> > +        return self._qmp_connection
> >
> >      @classmethod
> >      def _qmp_args(cls, _conv_keys: bool = True, **args: Any) -> Dict[str, 
> > Any]:
> >
>
> This patch breaks the EmptyCPUModel test:
>
> (043/101) tests/acceptance/empty_cpu_model.py:EmptyCPUModel.test:
> ERROR: Attempt to access QMP with no connection (0.03 s)

Fixed with:

-- >8 --
diff --git a/python/qemu/machine.py b/python/qemu/machine.py
index ba6397dd7e..26ae7be89b 100644
--- a/python/qemu/machine.py
+++ b/python/qemu/machine.py
@@ -480,7 +480,7 @@ def set_qmp_monitor(self, enabled: bool = True) -> None:

     @property
     def _qmp(self) -> qmp.QEMUMonitorProtocol:
-        if self._qmp_connection is None:
+        if self._qmp_set and self._qmp_connection is None:
             raise QEMUMachineError("Attempt to access QMP with no connection")
         return self._qmp_connection

---

Does that sound reasonable to you?