[Question] What is vars and allVars used for?

More of a question than a bug report: I discovered in the addVars method of the DefaultCodegen the following code snippet

        if (allProperties != null) {
            Set<String> allMandatory = allRequired == null ? Collections.emptySet()
                    : new TreeSet<>(allRequired);
            // update "vars" with parent's properties (all, required)
            addVars(m, m.allVars, allProperties, allMandatory);
            m.allMandatory = allMandatory;
        }

Why is vars updated with the properties from allVars? Doesn't vars contain only the properties from the schema objects properties-block in contrast to allVars, which contains cumulatively all properties from the parents plus the own properties?

Start with the DefaultCodegen.addVars method and trace how vars, allVars, allProperties, and allMandatory are populated. Check the related model-generation flow to determine whether the current behavior is intentional. Done means documenting the distinction and explaining why parent properties are passed through addVars.