OptaPlanner: does the Drools null-safe dereference operator not work in OptaPlanner DRL rules?

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According to the Drools v7.46.0.Final documentation for the null-safe dereferencing operator !., expressions of the form

Type( $data : property!.data )

are internally expanded/represented as:

Type( property != null, $data : property.data )

However, this does not seem to work in the context of OptaPlanner.

For the rule

Type( $data : property!.data )

the generated code is

package some.classes;

import static location.RulesAHASH1.*;
import org.optaplanner.core.api.score.buildin.bendablelong.BendableLongScoreHolder;
import org.drools.modelcompiler.dsl.pattern.D;

// other imports

@org.drools.compiler.kie.builder.MaterializedLambda()
public enum LambdaExtractorAHASH2 implements org.drools.model.functions.Function1<Type, java.lang.Long> {

    INSTANCE;

    public static final String EXPRESSION_HASH = "SOME_HASH";

    @Override()
    public java.lang.Long apply(Type _this) {
        return _this.getProperty() != null && _this.getProperty().getData();
    }
}

and given that data is not a boolean and apply has a return type of Long, this throws an exception.

The message:

java.lang.IllegalStateException: There are errors in a score DRL:
Error Messages:
Message [id=1, level=ERROR, path=blah/blah/blah/LambdaExtractorHASH.java, line=24, column=54
   text=bad operand types for binary operator '&&'
  first type:  boolean
  second type: java.lang.Long]

...

// generated code etc.

So, are we not supposed to use this notation when using Drools with OptaPlanner? Are there other language limitations?

Update:

Pulled the optaplanner repo, switched to 8.8.x, and modified a vehicleRoutingConstriants DRL rule to use the null-safe dereference operator:

rule "distanceToPreviousStandstill"
    when
        $customer : Customer($prevVehicle : previousStandstill!.vehicle, previousStandstill != null, $distanceFromPreviousStandstill : distanceFromPreviousStandstill)
    then
        System.out.println($prevVehicle);
        scoreHolder.addSoftConstraintMatch(kcontext, - $distanceFromPreviousStandstill);
end

This runs as expected.

optaplanner drools java
1 Answers

Updating to 8.8.x fixed the issue for me

Workaround:

replace the null dereference operator expression with what the internal representation is supposed to be, so, rather than writing this:

rule "name"
    when
        MyClass($subField : field!.subField)
        // more matching
    then
        // do some stuff
end

write this:

rule "name"
    when
        MyClass(field != null, $subField : field.subField)
        // more matching
    then
        // do some stuff
end
user_122977650
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