Re: [PATCH-next v2 1/1] lnst.Devices.Device: customize instance checks to support categorization

[Ondrej Lichtner]

On Fri, Jun 07, 2019 at 09:42:50AM +0200, csfakian(a)redhat.com wrote:
>  From: Christos Sfakianakis <csfakian(a)redhat.com&gt;
>  
>  Define a custom __instancecheck__ method that does special handling
>  for RemoteDevice instances defined on the controller. For such instances,
>  route the check via the _dev_cls attribute of the instance. For all
>  other cases, the handling remains the same as before.
>  
>  The result is the ability to differentiate between physical, soft and virtual
>  devices on the tester's side. A use case follows.
>  
>   #==============================================================
>   #Controller
>   #==============================================================
>  
>   from lnst.Devices import VlanDevice
>   from lnst.Devices.Device import Device as Dev
>   from lnst.Devices.VlanDevice import VlanDevice as VlanDev
>   from lnst.Devices.BridgeDevice import BridgeDevice as BridgeDev
>   from lnst.Devices.SoftDevice import SoftDevice as SoftDev
>   from lnst.Devices.VirtualDevice import VirtualDevice as VirtDev
>   ...
>          host1.eth0 = DeviceReq(label="net1",
> driver=RecipeParam("driver"))
>          host1.vlan0 = VlanDevice(realdev=host1.eth0, vlan_id=10)
>          x = host1.vlan0
>  
>          # Class hierarchy: Device >> SoftDevice >> VlanDevice
>          #                  Device >> SoftDevice >> MasterDevice >>
> BridgeDevice
>                                              #  Before | After
>                                              #------------------
>          isinstance(x, Dev)                  #  True   |  True
>          isinstance(x, SoftDev)              #  False  |  True
>          isinstance(x, VlanDev)              #  False  |  True
>          isinstance(x, BridgeDev)            #  False  |  False
>  
>          isinstance(host1.eth0, VirtDev)     #  True   |  True
>          isinstance(x, VirtDev)              #  False  |  False
>                                              #         |
>   #====================================================|=======
>   #Slave                                               |
>   #====================================================|=======
>          isinstance(dev, Dev)                #  True   |  True
>          isinstance(dev, SoftDev)            #  True   |  True
>          isinstance(dev, VlanDev)            #  True   |  True
>          isinstance(dev, BridgeDev)          #  False  |  False
>  
>  The result on the slave hasn't changed. The result on the controller
>  is now in agreement with that on the slave.
>  
>  Signed-off-by: Christos Sfakianakis <csfakian(a)redhat.com&gt;
>  ---
>   lnst/Devices/Device.py | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
>  
>  diff --git a/lnst/Devices/Device.py b/lnst/Devices/Device.py
>  index 30deb25..39d1dd2 100644
>  --- a/lnst/Devices/Device.py
>  +++ b/lnst/Devices/Device.py
>  @@ -30,7 +30,14 @@ from pyroute2.netlink.rtnl import RTM_NEWLINK
>   from pyroute2.netlink.rtnl import RTM_NEWADDR
>   from pyroute2.netlink.rtnl import RTM_DELADDR
>   
>  -class Device(object, metaclass=ABCMeta):
>  +class DeviceMeta(ABCMeta):
>  +    def __instancecheck__(self, other):
>  +        try:
>  +            return issubclass(other._dev_cls, self)
>  +        except AttributeError:
>  +            return super(DeviceMeta, self).__instancecheck__(other)
>  +
>  +class Device(object, metaclass=DeviceMeta):
>       """The base Device class
>   
>       Implemented using the pyroute2 package to access different attributes of
>  -- 
>  2.17.1
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This looks ok, pushed.

-Ondrej