error reporting for XML schemas

["Kyle F. Downey" <kd...@amberarcher.com>]

Hello,

When there's an error reported in TraverseSchema to do with the XML schema
definition itself being incorrect, this does not stop processing. As a
result, later on in the validator it will fail with a
NullPointerException.

For example, if you define a type

<complexType name="providerType">
  <attribute name="debug" type="boolean" use="optional"/>
  <all>
    <element ref="protocol"/>
    <element ref="host"/>
  </all>
</complexType>

TraverseSchema fails on its assertion that it have seen some kind of
"particle" (an element, an all, etc.) before it processes an attribute:

traversing complex Type : providerType,,.
 child element name debug
org.xml.sax.SAXParseException: Schema error:  complexType 'providerType'
with a elementOnly or mixed content need to have at least one particle
child.
	at
org.apache.xerces.framework.XMLParser.reportError(XMLParser.java:1065)
	at
org.apache.xerces.validators.schema.TraverseSchema.reportSchemaError(TraverseSchema.java:4628)
	at
org.apache.xerces.validators.schema.TraverseSchema.reportGenericSchemaError(TraverseSchema.java:4615)
	at
org.apache.xerces.validators.schema.TraverseSchema.traverseComplexTypeDecl(TraverseSchema.java:1953)


It then continues despite having a bad type definition and throws a
NullPointerException in XMLValidator:

java.lang.NullPointerException
	at
org.apache.xerces.validators.schema.SchemaGrammar.getElementComplexTypeInfo(SchemaGrammar.java:248)
	at
org.apache.xerces.validators.common.XMLValidator.validateElementAndAttributes(XMLValidator.java:2566)
	at
org.apache.xerces.validators.common.XMLValidator.callStartElement(XMLValidator.java:835)


By the time that bubbled up to JDOM, I had almost no information about the
cause. I kept on recompiling, turning on debugging and stack trace
printing features until I happened to notice that error further up and
corrected it (placing my attribute tag after the all). Shouldn't
TraverseSchema halt processing immediately if it can't define a type?

regards,
kd