tool_type.h

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#ifndef art_Utilities_detail_tool_type_h
#define art_Utilities_detail_tool_type_h

#include "canvas/Utilities/Exception.h"
#include "cetlib/BasicPluginFactory.h"

#include <functional>
#include <memory>
#include <string>
#include <type_traits>

namespace fhicl {
  class ParameterSet;
}

namespace art::detail {

  template <typename T, typename = void>
  struct tool_type;

  template <typename T>
  struct tool_type<T, std::enable_if_t<std::is_class<T>::value>> {
    using return_type = std::unique_ptr<T>;

    static auto
    make_plugin(cet::BasicPluginFactory& factory,
                std::string const& libspec,
                fhicl::ParameterSet const& pset)
    {
      return factory.makePlugin<std::unique_ptr<T>>(libspec, pset);
    }
  };

  template <typename T>
  struct tool_type<T, std::enable_if_t<std::is_function<T>::value>> {
    using return_type = std::function<T>;

    static auto
    make_plugin(cet::BasicPluginFactory& factory,
                std::string const& libspec,
                fhicl::ParameterSet const&,
                std::string const& function_plugin_type)
    {
      auto const pluginType = factory.pluginType(libspec);
      return pluginType == function_plugin_type ?
               factory.makePlugin<T>(libspec) :
               throw Exception(errors::Configuration,
                               "tool_type::make_plugin: ")
                 << "Unrecognized function-tool type \"" << function_plugin_type
                 << "\" for plugin \"" << libspec << "\".\n"
                 << "Allowed function-tool type for above plugin is: \""
                 << pluginType << "\".\n";
    }
  };

} // namespace art::detail

#endif /* art_Utilities_detail_tool_type_h */

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