Populate xsi:type attribute on toXML(...)

[abestel]

Context
I have an example here that reproduces the problem: https://github.com/abestel/scalaxb-failure/tree/bug/type_attribute

Basically, the WSDL defines types as:

    <wsdl:types>
        <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:ser="http://schemas.microsoft.com/2003/10/Serialization/" elementFormDefault="unqualified">
            <xs:complexType name="ServiceRequest">
                <xs:sequence>
                    <xs:element name="IP" nillable="true" type="xs:string"/>
                </xs:sequence>
            </xs:complexType>
            <xs:element name="ServiceRequest" nillable="true" type="ServiceRequest"/>

            <xs:complexType name="ServiceRequestResponse">
                <xs:sequence>
                    <xs:element name="IP" nillable="true" type="xs:string"/>
                </xs:sequence>
            </xs:complexType>
            <xs:element name="ServiceRequestResponse" nillable="true" type="ServiceRequestResponse"/>

            <xs:complexType name="MyRequest">
                <xs:complexContent mixed="false">
                    <xs:extension base="ServiceRequest">
                        <xs:sequence>
                            <xs:element name="ID" type="xs:int"/>
                        </xs:sequence>
                    </xs:extension>
                </xs:complexContent>
            </xs:complexType>
            <xs:element name="MyRequest" nillable="true" type="MyRequest"/>

            <xs:complexType name="MySubRequest">
                <xs:complexContent mixed="false">
                    <xs:extension base="MyRequest">
                        <xs:sequence/>
                    </xs:extension>
                </xs:complexContent>
            </xs:complexType>
            <xs:element name="MySubRequest" nillable="true" type="MySubRequest"/>
        </xs:schema>
    </wsdl:types>

So I have ServiceRequest <- MyRequest <- MySubRequest.
The inheritance is expressed as

• MyRequestable = MyRequest + MySubRequest
• ServiceRequestable = ServiceRequest + MyRequestable

The generated formats are:

  trait DefaultComtestgenerated_ServiceRequestableFormat extends scalaxb.XMLFormat[com.test.generated.ServiceRequestable] {
...
    
    def writes(__obj: com.test.generated.ServiceRequestable, __namespace: Option[String], __elementLabel: Option[String],
        __scope: scala.xml.NamespaceBinding, __typeAttribute: Boolean): scala.xml.NodeSeq = __obj match {
      case x: com.test.generated.MyRequestable => scalaxb.toXML[com.test.generated.MyRequestable](x, __namespace, __elementLabel, __scope, true)
      case x: com.test.generated.ServiceRequest => scalaxb.toXML[com.test.generated.ServiceRequest](x, __namespace, __elementLabel, __scope, false)
    }
  }

  trait DefaultComtestgenerated_MyRequestableFormat extends scalaxb.XMLFormat[com.test.generated.MyRequestable] {
...
    
    def writes(__obj: com.test.generated.MyRequestable, __namespace: Option[String], __elementLabel: Option[String],
        __scope: scala.xml.NamespaceBinding, __typeAttribute: Boolean): scala.xml.NodeSeq = __obj match {
      case x: com.test.generated.MySubRequest => scalaxb.toXML[com.test.generated.MySubRequest](x, __namespace, __elementLabel, __scope, true)
      case x: com.test.generated.MyRequest => scalaxb.toXML[com.test.generated.MyRequest](x, __namespace, __elementLabel, __scope, false)
    }
  }

Here is a very simple example to see the issue:

    val request: ServiceRequestable =
      MyRequest(
        IP = Some("127.0.0.1"),
        ID = 123,
      )

    val xml = toXML(
      request,
      "request",
      defaultScope
    )(Comtestgenerated_ServiceRequestableFormat)

The expected output would be:

<request xsi:type="MyRequest"
         xmlns:tns="http://tempuri.org/"
         xmlns:xs="http://www.w3.org/2001/XMLSchema"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <IP>127.0.0.1</IP>
    <ID>123</ID>
</request>

The issue is that xsi:type="MyRequest" is not present in the generated XML with the current version of ScalaXB.

Indeed, step by step, we have the following:

• (1) In DefaultComtestgenerated_ServiceRequestableFormat#writes, we match on case x: com.test.generated.MyRequestable and call another toXML with typeAttribute=true
• (2) in DefaultComtestgenerated_MyRequestableFormat#writes, we match on case x: com.test.generated.MyRequest and override typeAttribute to false

Proposal
Actually use the typeAttribute that is propagated. Indeed writes takes it as an argument, so for traits we can just reuse the value for default cases.

The generated code would be

  trait DefaultComtestgenerated_ServiceRequestableFormat extends scalaxb.XMLFormat[com.test.generated.ServiceRequestable] {
...
    
    def writes(__obj: com.test.generated.ServiceRequestable, __namespace: Option[String], __elementLabel: Option[String],
        __scope: scala.xml.NamespaceBinding, __typeAttribute: Boolean): scala.xml.NodeSeq = __obj match {
      case x: com.test.generated.MyRequestable => scalaxb.toXML[com.test.generated.MyRequestable](x, __namespace, __elementLabel, __scope, true)
      case x: com.test.generated.ServiceRequest => scalaxb.toXML[com.test.generated.ServiceRequest](x, __namespace, __elementLabel, __scope, __typeAttribute)
    }
  }

  trait DefaultComtestgenerated_MyRequestableFormat extends scalaxb.XMLFormat[com.test.generated.MyRequestable] {
...
    
    def writes(__obj: com.test.generated.MyRequestable, __namespace: Option[String], __elementLabel: Option[String],
        __scope: scala.xml.NamespaceBinding, __typeAttribute: Boolean): scala.xml.NodeSeq = __obj match {
      case x: com.test.generated.MySubRequest => scalaxb.toXML[com.test.generated.MySubRequest](x, __namespace, __elementLabel, __scope, true)
      case x: com.test.generated.MyRequest => scalaxb.toXML[com.test.generated.MyRequest](x, __namespace, __elementLabel, __scope, __typeAttribute)
    }
  }

In that case, the typeAttribute=true from step (1) would be reused in step (2) and the typeAttribute would actually be written.
The behavior of an operation taking a MyRequestable would not change (the typeAttribute would not be written in that case).

Note
Should solve #364 and I got inspired by #508

[eed3si9n]

Thanks! This makes more sense.