Generated code for Android Clusters does not properly handle optional values

[g-coppock]

Problem

In the generated cluster code (e.g. NetworkCommissioningClient-InvokeSubscribeImpl.cpp), an Optional<Long> is passed as an argument for the breadcrumb attribute for the generated cluster commands (e.g. addOrUpdateWiFiNetwork).

The generated code looks like:

if (breadcrumb != nullptr) {
    jobject optionalValue_0;
    chip::JniReferences::GetInstance().GetOptionalValue(breadcrumb, optionalValue_0);
    auto & definedValue_0 = request.breadcrumb.Emplace();
    definedValue_0 = static_cast<std::remove_reference_t<decltype(definedValue_0)>>(chip::JniReferences::GetInstance().LongToPrimitive(optionalValue_0));
}

However, this fails with a JNI error on the call to LongToPrimitive, as the optionalValue_0 (the unwrapped value from the Optional) may be null.

The generating code is here:
https://github.com/project-chip/connectedhomeip/blob/master/scripts/idl/generators/java/ChipClustersCpp.jinja

Proposed Solution

The generated code should probably look like:

if (breadcrumb != nullptr) {
    jobject optionalValue_0;
    chip::JniReferences::GetInstance().GetOptionalValue(breadcrumb, optionalValue_0);
    if (optionalValue_0 != nullptr) {
        auto & definedValue_0 = request.breadcrumb.Emplace();
        definedValue_0 = static_cast<std::remove_reference_t<decltype(definedValue_0)>>(chip::JniReferences::GetInstance().LongToPrimitive(optionalValue_0));
    }
}