package org.javarosa.xpath.expr;

import org.javarosa.core.model.condition.EvaluationContext;
import org.javarosa.core.model.instance.DataInstance;
import org.javarosa.core.util.externalizable.DeserializationException;
import org.javarosa.core.util.externalizable.PrototypeFactory;
import org.javarosa.xpath.XPathUnsupportedException;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

public class XPathUnionExpr extends XPathBinaryOpExpr {
    public XPathUnionExpr() {
    } //for deserialization

    public XPathUnionExpr(XPathExpression a, XPathExpression b) {
        super(-1, a, b);
    }

    @Override
    public Object evalRaw(DataInstance model, EvaluationContext evalContext) {
        throw new XPathUnsupportedException("nodeset union operation");
    }

    @Override
    public String toString() {
        return super.toString("union");
    }

    @Override
    public void readExternal(DataInputStream in, PrototypeFactory pf) throws IOException, DeserializationException {
        super.readExternal(in, pf);
    }

    @Override
    public void writeExternal(DataOutputStream out) throws IOException {
        super.writeExternal(out);
    }

    @Override
    public String toPrettyString() {
        return "unsupported union operation";
    }
}

package org.javarosa.xpath.expr;

import org.javarosa.core.model.condition.EvaluationContext;
import org.javarosa.core.model.instance.DataInstance;
import org.javarosa.core.util.externalizable.DeserializationException;
import org.javarosa.core.util.externalizable.PrototypeFactory;
import org.javarosa.xpath.XPathUnsupportedException;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

public class XPathUnionExpr extends XPathBinaryOpExpr {
    public XPathUnionExpr() {
    } //for deserialization

    public XPathUnionExpr(XPathExpression a, XPathExpression b) {
        super(-1, a, b);
    }

    @Override
    public Object evalRaw(DataInstance model, EvaluationContext evalContext) {
        throw new XPathUnsupportedException("nodeset union operation");
    }

    @Override
    public String toString() {
        return super.toString("union");
    }

    @Override
    public void readExternal(DataInputStream in, PrototypeFactory pf) throws IOException, DeserializationException {
        readExpressions(in, pf);
        op = -1;
    }

    @Override
    public void writeExternal(DataOutputStream out) throws IOException {
        writeExpressions(out);
    }

    @Override
    public String toPrettyString() {
        return "unsupported union operation";
    }
}

Fix externalization oversite that would have required a migration