Allow users to globally opt out of automatic lookup

docs/general/configuration_options.md

@@ -5,6 +5,7 @@ The following configuration options can be set on `ActiveModel::Serializer.confi
 ## General
 
 - `adapter`: The [adapter](adapters.md) to use. Possible values: `:attributes, :json, :json_api`. Default: `:attributes`.
+- `automatic_lookup`: Whether serializer should be automatically looked up or manually provided. Default: `true`
 
 ## JSON API
 

lib/action_controller/serialization.rb

@@ -21,6 +21,10 @@ module ActionController
     end
 
     def get_serializer(resource, options = {})
+      unless options[:serializer] || options[:each_serializer] || ActiveModel::Serializer.config.automatic_lookup
+        return resource
+      end
+
       if !use_adapter?
         warn 'ActionController::Serialization#use_adapter? has been removed. '\
           "Please pass 'adapter: false' or see ActiveSupport::SerializableResource.new"

lib/active_model/serializer/configuration.rb

@@ -20,6 +20,7 @@ module ActiveModel
 
         config.adapter = :attributes
         config.jsonapi_resource_type = :plural
+        config.automatic_lookup = true
       end
     end
   end