Class ValueEntry

eval/public/activation.h:105–136

 private:
  class ValueEntry {
   public:
    explicit ValueEntry(std::unique_ptr<CelValueProducer> prod)
        : value_(), producer_(std::move(prod)) {}

    explicit ValueEntry(const CelValue& value) : value_(value), producer_() {}

    // Retrieve associated CelValue.
    // If the value is not set and producer is set,
    // obtain and cache value from producer.
    absl::optional<CelValue> RetrieveValue(google::protobuf::Arena* arena) const {
      if (!value_.has_value()) {
        if (producer_) {
          value_ = producer_->Produce(arena);
        }
      }

      return value_;
    }

    bool ClearValue() {
      bool result = value_.has_value();
      value_.reset();
      return result;
    }

    bool HasProducer() const { return producer_ != nullptr; }

   private:
    mutable absl::optional<CelValue> value_;
    std::unique_ptr<CelValueProducer> producer_;
  };

  friend class cel::runtime_internal::ActivationAttributeMatcherAccess;