Saxon

Putting together a test case for this, I actually managed to get a NullPointerException in XSDImport when importing a no-namespace schema from one with a namespace which was in turn loaded using xsi:schemaLocation.

This is achieved by running Validate from the command line with -xsd:test.xsd -s:test.xml -t -xsdversion:1.1 -xsiloc:on and the following three files in the current directory:

test.xsd

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" version="1.1">
    <xs:element name="foo" type="barType"/>     
    <xs:simpleType name="barType">
        <xs:restriction base="xs:integer">
            <xs:minExclusive value="5"/>
        </xs:restriction>       
    </xs:simpleType>    
</xs:schema>

test2.xsd

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:tn="foo" targetNamespace="foo" elementFormDefault="qualified">
   <xs:import schemaLocation="test.xsd"/>
	<xs:complexType name="bazType">
		<xs:simpleContent>
			<xs:extension base="barType">
				<xs:attribute name="code" type="xs:integer"/>
			</xs:extension>
		</xs:simpleContent>
	</xs:complexType>	
</xs:schema>

test.xml

<foo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
   xsi:schemaLocation="foo test2.xsd" code="42" xsi:type="foo:bazType" xmlns:foo="foo">23</foo>

It's failing trying to output the warning message

"The schema document at " + schemaLocation +
                        " is not being read because schema components for this namespace are already available"

because namespace is null. Easily fixed.

With this fixed, the test runs successfully (document is valid) if xsi:schemaLocation precedes xsi:type, and fails saying Unknown type {foo:bazType} specified in xsi:type attribute if the order of attributes is reversed. (The parser I'm using appears to deliver attributes in the order they are written).