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
# jsonrpc.py
# original code: http://trac.pyworks.org/pyjamas/wiki/DjangoWithPyJamas
# also from: http://www.pimentech.fr/technologies/outils
from __future__ import absolute_import
import datetime
from django.core.serializers import serialize
from svgui.pyjs.jsonrpc.jsonrpc import JSONRPCServiceBase
# JSONRPCService and jsonremote are used in combination to drastically
# simplify the provision of JSONRPC services. use as follows:
#
# jsonservice = JSONRPCService()
#
# @jsonremote(jsonservice)
# def test(request, echo_param):
# return "echoing the param back: %s" % echo_param
#
# dump jsonservice into urlpatterns:
# (r'^service1/$', 'djangoapp.views.jsonservice'),
class JSONRPCService(JSONRPCServiceBase):
def __call__(self, request, extra=None):
return self.process(request.raw_post_data)
def jsonremote(service):
"""Make JSONRPCService a decorator so that you can write :
from jsonrpc import JSONRPCService
chatservice = JSONRPCService()
@jsonremote(chatservice)
def login(request, user_name):
(...)
"""
def remotify(func):
if isinstance(service, JSONRPCService):
service.add_method(func.__name__, func)
else:
emsg = 'Service "%s" not found' % str(service.__name__)
raise NotImplementedError(emsg)
return func
return remotify
# FormProcessor provides a mechanism for turning Django Forms into JSONRPC
# Services. If you have an existing Django app which makes prevalent
# use of Django Forms it will save you rewriting the app.
# use as follows. in djangoapp/views.py :
#
# class SimpleForm(forms.Form):
# testfield = forms.CharField(max_length=100)
#
# class SimpleForm2(forms.Form):
# testfield = forms.CharField(max_length=20)
#
# processor = FormProcessor({'processsimpleform': SimpleForm,
# 'processsimpleform2': SimpleForm2})
#
# this will result in a JSONRPC service being created with two
# RPC functions. dump "processor" into urlpatterns to make it
# part of the app:
# (r'^formsservice/$', 'djangoapp.views.processor'),
def builderrors(form):
d = {}
for error in form.errors.keys():
if error not in d:
d[error] = []
for errorval in form.errors[error]:
d[error].append(unicode(errorval))
return d
# contains the list of arguments in each field
field_names = {
'CharField': ['max_length', 'min_length'],
'IntegerField': ['max_value', 'min_value'],
'FloatField': ['max_value', 'min_value'],
'DecimalField': ['max_value', 'min_value', 'max_digits', 'decimal_places'],
'DateField': ['input_formats'],
'DateTimeField': ['input_formats'],
'TimeField': ['input_formats'],
'RegexField': ['max_length', 'min_length'], # sadly we can't get the expr
'EmailField': ['max_length', 'min_length'],
'URLField': ['max_length', 'min_length', 'verify_exists', 'user_agent'],
'ChoiceField': ['choices'],
'FilePathField': ['path', 'match', 'recursive', 'choices'],
'IPAddressField': ['max_length', 'min_length'],
}
def describe_field_errors(field):
res = {}
field_type = field.__class__.__name__
msgs = {}
for n, m in field.error_messages.items():
msgs[n] = unicode(m)
res['error_messages'] = msgs
if field_type in ['ComboField', 'MultiValueField', 'SplitDateTimeField']:
res['fields'] = map(describe_field, field.fields)
return res
def describe_fields_errors(fields, field_names):
res = {}
if not field_names:
field_names = fields.keys()
for name in field_names:
field = fields[name]
res[name] = describe_field_errors(field)
return res
def describe_field(field):
res = {}
field_type = field.__class__.__name__
for fname in (field_names.get(field_type, []) +
['help_text', 'label', 'initial', 'required']):
res[fname] = getattr(field, fname)
if field_type in ['ComboField', 'MultiValueField', 'SplitDateTimeField']:
res['fields'] = map(describe_field, field.fields)
return res
def describe_fields(fields, field_names):
res = {}
if not field_names:
field_names = fields.keys()
for name in field_names:
field = fields[name]
res[name] = describe_field(field)
return res
class FormProcessor(JSONRPCService):
def __init__(self, forms, _formcls=None):
if _formcls is None:
JSONRPCService.__init__(self)
for k in forms.keys():
s = FormProcessor({}, forms[k])
self.add_method(k, s.__process)
else:
JSONRPCService.__init__(self, forms)
self.formcls = _formcls
def __process(self, request, params, command=None):
f = self.formcls(params)
if command is None: # just validate
if not f.is_valid():
return {'success': False, 'errors': builderrors(f)}
return {'success': True}
elif 'describe_errors' in command:
field_names = command['describe_errors']
return describe_fields_errors(f.fields, field_names)
elif 'describe' in command:
field_names = command['describe']
return describe_fields(f.fields, field_names)
elif 'save' in command:
if not f.is_valid():
return {'success': False, 'errors': builderrors(f)}
instance = f.save() # XXX: if you want more, over-ride save.
return {'success': True, 'instance': json_convert(instance)}
elif 'html' in command:
return {'success': True, 'html': f.as_table()}
return "unrecognised command"
# The following is incredibly convenient for saving vast amounts of
# coding, avoiding doing silly things like this:
# jsonresult = {'field1': djangoobject.field1,
# 'field2': djangoobject.date.strftime('%Y.%M'),
# ..... }
#
# The date/time flatten function is there because JSONRPC doesn't
# support date/time objects or formats, so conversion to a string
# is the most logical choice. pyjamas, being python, can easily
# be used to parse the string result at the other end.
#
# use as follows:
#
# jsonservice = JSONRPCService()
#
# @jsonremote(jsonservice)
# def list_some_model(request, start=0, count=10):
# l = SomeDjangoModelClass.objects.filter()
# res = json_convert(l[start:end])
#
# @jsonremote(jsonservice)
# def list_another_model(request, start=0, count=10):
# l = AnotherDjangoModelClass.objects.filter()
# res = json_convert(l[start:end])
#
# dump jsonservice into urlpatterns to make the two RPC functions,
# list_some_model and list_another_model part of the django app:
# (r'^service1/$', 'djangoapp.views.jsonservice'),
def dict_datetimeflatten(item):
d = {}
for k, v in item.items():
k = str(k)
if isinstance(v, datetime.date):
d[k] = str(v)
elif isinstance(v, dict):
d[k] = dict_datetimeflatten(v)
else:
d[k] = v
return d
def json_convert(l, fields=None):
res = []
for item in serialize('python', l, fields=fields):
res.append(dict_datetimeflatten(item))
return res