Method MergeInto

cpp/src/arrow/filesystem/filesystem.cc:755–787

  }

  Status MergeInto(FileSystemFactoryRegistry* main_registry) {
    std::unique_lock lock{mutex_};
    RETURN_NOT_OK(CheckValid());

    std::unique_lock main_lock{main_registry->mutex_};
    RETURN_NOT_OK(main_registry->CheckValid());

    std::vector<std::string_view> duplicated_schemes;
    for (auto& [scheme, registered] : scheme_to_factory_) {
      if (!registered.ok()) {
        duplicated_schemes.emplace_back(scheme);
        continue;
      }

      auto [it, success] =
          main_registry->scheme_to_factory_.emplace(std::move(scheme), registered);
      if (success) continue;

      if (it->second.ok()) {
        if (registered->factory == it->second->factory) continue;
      }

      duplicated_schemes.emplace_back(it->first);
    }
    scheme_to_factory_.clear();
    merged_into_ = main_registry;

    if (duplicated_schemes.empty()) return Status::OK();
    return Status::KeyError("Attempted to register ", duplicated_schemes.size(),
                            " factories for schemes ['",
                            arrow::internal::JoinStrings(duplicated_schemes, "', '"),
                            "'] but those schemes were already registered.");
  }

  void EnsureFinalized() {
    std::unique_lock lock{mutex_};