beremiz

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

2018-08-24, Andrey Skvortsov
96ca6b056c55
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
<?xml version='1.0' encoding='utf-8'?>
<PyFile xmlns:xhtml="http://www.w3.org/1999/xhtml">
<variables>
<variable name="Test_Python_Var" type="INT" initial="4"/>
<variable name="Second_Python_Var" type="INT" initial="5"/>
</variables>
<globals>
<xhtml:p><![CDATA[
import time,sys,ctypes
Python_to_C_Call = PLCBinary.Python_to_C_Call
Python_to_C_Call.restype = ctypes.c_int
Python_to_C_Call.argtypes = [ctypes.c_int, ctypes.POINTER(ctypes.c_int)]
def MyPythonFunc(arg):
i = ctypes.c_int()
if(Python_to_C_Call(arg, i)):
res = i.value
print "toC:", arg, "from C:", res, "FBID:", FBID
else:
print "Failed Python_to_C_Call failed"
res = None
print "Python read PLC global :",PLCGlobals.Test_Python_Var
PLCGlobals.Second_Python_Var = 789
sys.stdout.flush()
return res
async_error_test_code = """
def badaboom():
tuple()[0]
import wx
def badaboomwx():
wx.CallAfter(badaboom)
from threading import Timer
a = Timer(3, badaboom)
a.start()
b = Timer(6, badaboomwx)
b.start()
"""
]]></xhtml:p>
</globals>
<init>
<xhtml:p><![CDATA[
global x, y
x = 2
y = 5
print "py_runtime init:", x, ",", y
]]></xhtml:p>
</init>
<cleanup>
<xhtml:p><![CDATA[
print "py_runtime cleanup"
]]></xhtml:p>
</cleanup>
<start>
<xhtml:p><![CDATA[
global x, y
print "py_runtime start", x * x + y * y
]]></xhtml:p>
</start>
<stop>
<xhtml:p><![CDATA[
print "py_runtime stop"
]]></xhtml:p>
</stop>
</PyFile>