class Standard::Plugin::DeterminesClassConstant

def call(plugin_name, user_config)
  require_plugin(user_config["require_path"])
  if (constant_name = user_config["plugin_class_name"])
    begin
      Kernel.const_get(constant_name)
    rescue
      raise "Failed while configuring plugin `#{plugin_name}': no constant with name `#{constant_name}' was found"
    end
  else
    begin
      Kernel.const_get(Gem.loaded_specs[plugin_name].metadata["default_lint_roller_plugin"])
    rescue LoadError, StandardError
      raise <<~MSG
        Failed loading plugin `#{plugin_name}' because we couldn't determine
        the corresponding plugin class to instantiate.
        Standard plugin class names must either be:
          - If the plugin is a gem, defined in the gemspec as `default_lint_roller_plugin'
            spec.metadata["default_lint_roller_plugin"] = "MyModule::Plugin"
          - Set in YAML as `plugin_class_name'; example:
            plugins:
              - incomplete:
                  require_path: my_module/plugin
                  plugin_class_name: "MyModule::Plugin"
      MSG
    end
  end
end

def require_plugin(require_path)
  return if require_path.nil?
  begin
    require require_path
  rescue LoadError
    # If require_path isn't on the load_path (and it may be hard to get it
    # on there since standardrb is a cli), let's give folks a break and
    # also try to load it via the current working directory. This is
    # tested in test/standardrb_test.rb #test_plugins_options
    require Pathname.new(Dir.pwd).join(require_path)
  end
end