beremiz

Proper fix for error 'object has no attribute 'getSlave' in EtherCAT extension

2018-08-24, Andrey Skvortsov
96ca6b056c55
file isExecutable
Proper fix for error 'object has no attribute 'getSlave' in EtherCAT extension

traceback:
File "/home/developer/WorkData/PLC/beremiz/beremiz/IDEFrame.py", line 1433, in OnPouSelectedChanged
window.RefreshView()
File "/home/developer/WorkData/PLC/beremiz/beremiz/etherlab/ConfigEditor.py", line 837, in RefreshView
self.RefreshProcessVariables()
File "/home/developer/WorkData/PLC/beremiz/beremiz/etherlab/ConfigEditor.py", line 886, in RefreshProcessVariables
slaves = self.Controler.GetSlaves(**self.CurrentNodesFilter)
File "/home/developer/WorkData/PLC/beremiz/beremiz/etherlab/EthercatMaster.py", line 341, in GetSlaves
for slave in self.Config.getConfig().getSlave():
:_'lxml.etree._Element'_object_has_no_attribute_'getSlave'

Steps to reproduce problem:

- Add new EtherCAT master
- Add new EthercatNode to the master
- double click on


Revert commit "Dirty fix for error '_object_has_no_attribute_'getSlave' in EtherCAT extension"
[a3ac46366b86a0b237dac93be6b2281ac70b98a8].

The problem was that XML elements (proxy object) in some cases were created using custom XML
classes constructors and lxml.etree.Element() call and live python
patching. This causes that lxml backend doesn't know that custom python class
should be used for these XML elements.
Proxy object can be move/deleted and recreated by lxml
backend at any point in time or this can be done in python by copy/deepcopy operations.
If this happens, then newly created
proxy elements are using default class lxml.etree._Element. And all
custom functionality is lost.

All created XML elements should be always created through corresponding
parser and class lookup callback done by lxml backend.
It's described in more details in lxml documentation:
https://lxml.de/element_classes.html
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# This file is part of Beremiz runtime.
#
# Copyright (C) 2007: Edouard TISSERANT and Laurent BESSARD
#
# See COPYING.Runtime file for copyrights details.
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# Lesser General Public License for more details.
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
from __future__ import absolute_import
from __future__ import print_function
import socket
import threading
import zeroconf
service_type = '_PYRO._tcp.local.'
class ServicePublisher(object):
def __init__(self):
# type: fully qualified service type name
self.serviceproperties = {'description': 'Beremiz remote PLC'}
self.name = None
self.ip_32b = None
self.port = None
self.server = None
self.service_name = None
self.retrytimer = None
def RegisterService(self, name, ip, port):
try:
self._RegisterService(name, ip, port)
except Exception:
self.retrytimer = threading.Timer(2, self.RegisterService, [name, ip, port])
self.retrytimer.start()
def _RegisterService(self, name, ip, port):
# name: fully qualified service name
self.service_name = 'Beremiz_%s.%s' % (name, service_type)
self.name = name
self.port = port
self.server = zeroconf.Zeroconf()
print("MDNS brodcasting on :" + ip)
if ip == "0.0.0.0":
ip = self.gethostaddr()
print("MDNS brodcasted service address :" + ip)
self.ip_32b = socket.inet_aton(ip)
self.server.register_service(
zeroconf.ServiceInfo(service_type,
self.service_name,
self.ip_32b,
self.port,
properties=self.serviceproperties))
self.retrytimer = None
def UnRegisterService(self):
if self.retrytimer is not None:
self.retrytimer.cancel()
if self.server is not None:
self.server.unregister_service(
zeroconf.ServiceInfo(service_type,
self.service_name,
self.ip_32b,
self.port,
properties=self.serviceproperties))
self.server.close()
self.server = None
def gethostaddr(self, dst='224.0.1.41'):
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
try:
s.connect((dst, 7))
(host, _port) = s.getsockname()
s.close()
if host != '0.0.0.0':
return host
except Exception:
pass
return socket.gethostbyname(socket.gethostname())