Failed validation: XsdFieldSelector(path='@trigger|@attime') field selects multiple values #418
Description
Hi,
I have an XML with events defined that can occur when a certain trigger from a third system arrives or at a given fixed time. For that, we wanted to have a single event element type definition with several attributes, two of them, trigger or attime, mutually exclusive. In order to implement that I found this solution:
. . .
<xs:element type="eventType" name="event" maxOccurs="unbounded" minOccurs="0">
<xs:key name="attributeKey">
<xs:selector xpath="."/>
<xs:field xpath="@trigger|@attime"/>
</xs:key>
</xs:element>
. . .So, I created a file compliant with this schema, with event nodes having either trigger or attime attribute, but not both, and another one with a failing instance of event, with trigger and attime at the same time.
The problem is that both failed, and XMLSchema.validate() raises in both cases an exception for a valid event instance (with only the trigger attribute), as follows:
Traceback (most recent call last):
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/elements.py", line 911, in collect_key_fields
xsd_fields = identity.get_fields(xsd_element.xpath_node)
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/identities.py", line 331, in get_fields
raise XMLSchemaValueError(msg % field)
xmlschema.exceptions.XMLSchemaValueError: XsdFieldSelector(path='@trigger|@attime') field selects multiple values!
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/home/user/trigev/etc/trigev/schema/./validate.py", line 12, in <module>
raise(ee)
File "/home/user/trigev/etc/trigev/schema/./validate.py", line 9, in <module>
isvalid = schema.validate(sys.argv[2])
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/schemas.py", line 1698, in validate
for error in self.iter_errors(source, path, schema_path, use_defaults,
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/schemas.py", line 1829, in iter_errors
for result in xsd_element.iter_decode(elem, **kwargs):
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/elements.py", line 739, in iter_decode
for result in content_decoder.iter_decode(obj, validation, **kwargs):
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/groups.py", line 1050, in iter_decode
for result in xsd_element.iter_decode(child, validation, **kwargs):
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/elements.py", line 739, in iter_decode
for result in content_decoder.iter_decode(obj, validation, **kwargs):
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/groups.py", line 1050, in iter_decode
for result in xsd_element.iter_decode(child, validation, **kwargs):
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/elements.py", line 836, in iter_decode
yield from self.collect_key_fields(obj, xsd_type, validation, nilled, **kwargs)
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/elements.py", line 922, in collect_key_fields
yield self.validation_error(validation, err, obj, **kwargs)
File "/home/user/venv/lib/python3.10/site-packages/xmlschema/validators/xsdbase.py", line 249, in validation_error
raise error
xmlschema.validators.exceptions.XMLSchemaValidationError: failed validating <Element 'event' at 0x71e1d337c040> with XsdElement(name='event', occurs=[0, None]):
Reason: XsdFieldSelector(path='@trigger|@attime') field selects multiple values!
Schema component:
<xs:element xmlns:xs="http://www.w3.org/2001/XMLSchema" type="eventType" name="event" maxOccurs="unbounded" minOccurs="0">
<xs:key name="attributeKey">
<xs:selector xpath="." />
<xs:field xpath="@trigger|@attime" />
</xs:key>
</xs:element>
Instance type: <class 'xml.etree.ElementTree.Element'>
Instance:
<event trigger="TS01" command="powu56.py" parameters="-on -ports '1,2,3'" />
Path: /mqttservices/events/event[1]
I checked everything with xmllint and in that case everything works as expected, that is, the valid XML file validates, and the failing one fails to validate, and the correct reason is provided. But, of course, I would like to use a Python solution like xmlschema.
Please, find attached the sample XML and XSD files, as well as a very simplistic Python script.