Improve parsing of ComplexTypeSimpleContent according to XSD rules.

[veewee]

Q	A
Type	bug
BC Break	no
Fixed issues

Summary

Given a schema that is similar to this one:

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
           xmlns:tns="http://foo"
           targetNamespace="http://foo"
           elementFormDefault="qualified">
    <xsd:element name="sshOptions" type="tns:SshAuthenticationSettings" />
 
    <xsd:complexType name="SshAuthenticationSettings">
        <xsd:simpleContent>
            <xsd:extension base="xsd:string"
                <xsd:attribute name="method" type="xsd:string" />
                <xsd:attribute name="contentType" type="xsd:string" use="optional" />
            </xsd:extension>
        </xsd:simpleContent>
    </xsd:complexType>

</xsd:schema>

This:

<sshOptions xmlns="http://foo" contentType="filePath" method="password" />

Results in an empty string '' instead of null.

Only when the element is nillable and contains xsi:nil="true", it will result in null.
This makes it consistent in how it is described in the XSD spec.

It behaves correctly according to tests on an XSD validator:

• When the simpleContent extends int and no value is provided:
  • => cvc-datatype-valid.1.2.1: '' is not a valid value for 'integer'.
• When the simpleContent extends int and xsi:nil=true is provided without nillable in xsd:
  • => Attribute 'http://www.w3.org/2001/XMLSchema-instance,nil' must not appear on element 'sshOptions', because the {nillable} property of 'sshOptions' is false.
• When the simpleContent extends int and xsi:nil=true is provided us nillable in xsd:
  • => OK