FP java:S2637 for NonNull return type used in Optional.map(...).orElse(null)

[blazar (Rafał)]

False positive when method return value is marked with Lombok NonNull and it is used in Optional.map(…).orElse(null). It should not be raised because no value marked as @NonNull is assigned here, only read, and also the value is never null.

Rule affected: java:S2637 ["@NonNull" values should not be set to null]
SonarQube version 9.2.2 (build 50622)
SonarLint plugin 6.3.1.40498 in IntelliJ 2021.1.3
Java 17

Example:

import java.util.Optional;
import lombok.NonNull;

public class A {
    private final String value = "value";

    @NonNull // when this is removed the error disappears
    public String getValue() {
        return value;
    }


    public static void main(String[] args) {
        Optional<A> a = Optional.empty();
        System.out.println(
            a.map(A::getValue)
                .orElse(null)   // here is an error
        );
    }
}

[SebastianHungerecker]

Hi @blazar,

Thank you for your report and the reproducer. Indeed, this is a false positive. There seems to be a bug that causes SonarQube to think that orElse's parameter is marked @NonNull when it’s not. I’ve created a ticket for this bug.

Cheers,
Sebastian