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'?>
<project xmlns:ns1="http://www.plcopen.org/xml/tc6_0201" xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.plcopen.org/xml/tc6_0201">
<fileHeader companyName="Beremiz" productName="Beremiz" productVersion="1" creationDateTime="2018-07-27T13:19:12"/>
<contentHeader name="Modbus" modificationDateTime="2018-07-27T15:43:56">
<coordinateInfo>
<fbd>
<scaling x="0" y="0"/>
</fbd>
<ld>
<scaling x="0" y="0"/>
</ld>
<sfc>
<scaling x="0" y="0"/>
</sfc>
</coordinateInfo>
</contentHeader>
<types>
<dataTypes/>
<pous>
<pou name="program0" pouType="program">
<interface>
<localVars>
<variable name="Counter">
<type>
<INT/>
</type>
</variable>
<variable name="CounterReadBack">
<type>
<INT/>
</type>
</variable>
</localVars>
<localVars>
<variable name="MasterWriteToReg0" address="%QW0.0.0.0">
<type>
<INT/>
</type>
</variable>
<variable name="MasterReadFromReg1" address="%IW0.0.1.0">
<type>
<INT/>
</type>
</variable>
<variable name="SlaveHoldReg0" address="%IW0.1.0.0">
<type>
<WORD/>
</type>
</variable>
<variable name="SlaveInputReg0" address="%QW0.1.1.0">
<type>
<WORD/>
</type>
</variable>
</localVars>
<localVars>
<variable name="CTU0">
<type>
<derived name="CTU"/>
</type>
</variable>
<variable name="Generator0">
<type>
<derived name="Generator"/>
</type>
</variable>
</localVars>
</interface>
<body>
<FBD>
<comment localId="4" height="109" width="350">
<position x="102" y="438"/>
<content>
<xhtml:p><![CDATA[Modbus TCP Master writes counter value to one holding register on Modbus TCP Slave and reads it back from other input register.]]></xhtml:p>
</content>
</comment>
<comment localId="3" height="407" width="680">
<position x="21" y="15"/>
<content>
<xhtml:p><![CDATA[This examples shows how to work with Modbus extension. It uses Modbus TCP, but the same functions are available for Modbus RTU as well. Buth protocols are supported.
Modbus extensions requires native Modbus RTU/TCP library to be installed nearby Beremiz.
Following directory structure is expected:
<Parent directory>
"beremiz"
"Modbus"
If Modbus library is installed elsewhere, then place corresponding paths
in CFLAGS/LDFLAGS in project settings.
For GNU/Linux to install Modbus library in parent directory run following commands:
$ hg clone https://bitbucket.org/mjsousa/modbus Modbus
$ cd Modbus
$ make
After that Modbus extension is ready to be used in Beremiz projects.]]></xhtml:p>
</content>
</comment>
<block localId="5" typeName="CTU" instanceName="CTU0" executionOrderId="0" height="80" width="52">
<position x="346" y="605"/>
<inputVariables>
<variable formalParameter="CU" edge="rising">
<connectionPointIn>
<relPosition x="0" y="30"/>
<connection refLocalId="6" formalParameter="OUT">
<position x="346" y="635"/>
<position x="303" y="635"/>
</connection>
</connectionPointIn>
</variable>
<variable formalParameter="R">
<connectionPointIn>
<relPosition x="0" y="50"/>
</connectionPointIn>
</variable>
<variable formalParameter="PV">
<connectionPointIn>
<relPosition x="0" y="70"/>
<connection refLocalId="7">
<position x="346" y="675"/>
<position x="324" y="675"/>
<position x="324" y="703"/>
<position x="302" y="703"/>
</connection>
</connectionPointIn>
</variable>
</inputVariables>
<inOutVariables/>
<outputVariables>
<variable formalParameter="Q">
<connectionPointOut>
<relPosition x="52" y="30"/>
</connectionPointOut>
</variable>
<variable formalParameter="CV">
<connectionPointOut>
<relPosition x="52" y="50"/>
</connectionPointOut>
</variable>
</outputVariables>
</block>
<block localId="6" typeName="Generator" instanceName="Generator0" executionOrderId="0" height="60" width="79">
<position x="224" y="605"/>
<inputVariables>
<variable formalParameter="PON">
<connectionPointIn>
<relPosition x="0" y="30"/>
<connection refLocalId="1">
<position x="224" y="635"/>
<position x="154" y="635"/>
</connection>
</connectionPointIn>
</variable>
<variable formalParameter="POFF">
<connectionPointIn>
<relPosition x="0" y="50"/>
<connection refLocalId="1">
<position x="224" y="655"/>
<position x="189" y="655"/>
<position x="189" y="635"/>
<position x="154" y="635"/>
</connection>
</connectionPointIn>
</variable>
</inputVariables>
<inOutVariables/>
<outputVariables>
<variable formalParameter="OUT">
<connectionPointOut>
<relPosition x="79" y="30"/>
</connectionPointOut>
</variable>
</outputVariables>
</block>
<inVariable localId="1" executionOrderId="0" height="30" width="138" negated="false">
<position x="16" y="620"/>
<connectionPointOut>
<relPosition x="138" y="15"/>
</connectionPointOut>
<expression>T#1s</expression>
</inVariable>
<inVariable localId="7" executionOrderId="0" height="30" width="138" negated="false">
<position x="164" y="688"/>
<connectionPointOut>
<relPosition x="138" y="15"/>
</connectionPointOut>
<expression>32767</expression>
</inVariable>
<inOutVariable localId="2" executionOrderId="0" height="30" width="138" negatedOut="false" negatedIn="false">
<position x="544" y="640"/>
<connectionPointIn>
<relPosition x="0" y="15"/>
<connection refLocalId="5" formalParameter="CV">
<position x="544" y="655"/>
<position x="398" y="655"/>
</connection>
</connectionPointIn>
<connectionPointOut>
<relPosition x="138" y="15"/>
</connectionPointOut>
<expression>Counter</expression>
</inOutVariable>
<outVariable localId="8" executionOrderId="0" height="30" width="138" negated="false">
<position x="762" y="640"/>
<connectionPointIn>
<relPosition x="0" y="15"/>
<connection refLocalId="2">
<position x="762" y="655"/>
<position x="682" y="655"/>
</connection>
</connectionPointIn>
<expression>MasterWriteToReg0</expression>
</outVariable>
<inVariable localId="9" executionOrderId="0" height="30" width="152" negated="false">
<position x="81" y="747"/>
<connectionPointOut>
<relPosition x="152" y="15"/>
</connectionPointOut>
<expression>MasterReadFromReg1</expression>
</inVariable>
<outVariable localId="10" executionOrderId="0" height="30" width="137" negated="false">
<position x="547" y="747"/>
<connectionPointIn>
<relPosition x="0" y="15"/>
<connection refLocalId="9">
<position x="547" y="762"/>
<position x="233" y="762"/>
</connection>
</connectionPointIn>
<expression>CounterReadBack</expression>
</outVariable>
<comment localId="11" height="109" width="350">
<position x="85" y="825"/>
<content>
<xhtml:p><![CDATA[Modbus TCP Slave just copies received register value from holding register to input register.]]></xhtml:p>
</content>
</comment>
<inVariable localId="12" executionOrderId="0" height="30" width="152" negated="false">
<position x="82" y="970"/>
<connectionPointOut>
<relPosition x="152" y="15"/>
</connectionPointOut>
<expression>SlaveHoldReg0</expression>
</inVariable>
<outVariable localId="13" executionOrderId="0" height="30" width="123" negated="false">
<position x="548" y="970"/>
<connectionPointIn>
<relPosition x="0" y="15"/>
<connection refLocalId="12">
<position x="548" y="985"/>
<position x="234" y="985"/>
</connection>
</connectionPointIn>
<expression>SlaveInputReg0</expression>
</outVariable>
</FBD>
</body>
</pou>
<pou name="Generator" pouType="functionBlock">
<interface>
<outputVars>
<variable name="OUT">
<type>
<BOOL/>
</type>
</variable>
</outputVars>
<inputVars>
<variable name="PON">
<type>
<TIME/>
</type>
</variable>
<variable name="POFF">
<type>
<TIME/>
</type>
</variable>
</inputVars>
<localVars>
<variable name="T1">
<type>
<derived name="TON"/>
</type>
</variable>
<variable name="T2">
<type>
<derived name="TOF"/>
</type>
</variable>
</localVars>
</interface>
<body>
<ST>
<xhtml:p><![CDATA[T1( IN := NOT T2.Q, PT := POFF);
T2( IN := T1.Q, PT := PON);
OUT := T2.Q;]]></xhtml:p>
</ST>
</body>
</pou>
</pous>
</types>
<instances>
<configurations>
<configuration name="config">
<resource name="resource1">
<task name="task0" priority="0" interval="T#20ms">
<pouInstance name="instance0" typeName="program0"/>
</task>
</resource>
</configuration>
</configurations>
</instances>
</project>