Function PerformLookup

eval/eval/container_access_step.cc:222–273

}

void PerformLookup(ExecutionFrameBase& frame, const Value& container,
                   const Value& key, const AttributeTrail& container_trail,
                   bool enable_optional_types, Value& result,
                   AttributeTrail& trail) {
  if (frame.unknown_processing_enabled()) {
    AttributeUtility::Accumulator unknowns =
        frame.attribute_utility().CreateAccumulator();
    unknowns.MaybeAdd(container);
    unknowns.MaybeAdd(key);

    if (!unknowns.IsEmpty()) {
      result = std::move(unknowns).Build();
      return;
    }

    trail = container_trail.Step(AttributeQualifierFromValue(key));

    if (frame.attribute_utility().CheckForUnknownExact(trail)) {
      result = frame.attribute_utility().CreateUnknownSet(trail.attribute());
      return;
    }
  }

  if (InstanceOf<ErrorValue>(container)) {
    result = container;
    return;
  }
  if (InstanceOf<ErrorValue>(key)) {
    result = key;
    return;
  }

  if (enable_optional_types && container.IsOptional()) {
    const auto& optional_value = container.GetOptional();
    if (!optional_value.HasValue()) {
      result = cel::OptionalValue::None();
      return;
    }
    Value value;
    optional_value.Value(&value);
    LookupInContainer(value, key, frame, result);
    if (auto error_value = cel::As<cel::ErrorValue>(result);
        error_value && cel::IsNoSuchKey(*error_value)) {
      result = cel::OptionalValue::None();
      return;
    }
    result = cel::OptionalValue::Of(std::move(result), frame.arena());
    return;
  }

  LookupInContainer(container, key, frame, result);
}

// ContainerAccessStep performs message field access specified by Expr::Select
// message.