Replace fail/rescue CollectionSerializer::NoSerializerError with throw/catch :no_serializer (#1767)

CHANGELOG.md

@@ -25,6 +25,8 @@ Fixes:
 - [#1881](https://github.com/rails-api/active_model_serializers/pull/1881) ActiveModelSerializers::Model correctly works with string keys (@yevhene)
 
 Misc:
+- [#1767](https://github.com/rails-api/active_model_serializers/pull/1767) Replace raising/rescuing `CollectionSerializer::NoSerializerError`,
+  throw/catch `:no_serializer`. (@bf4)
 - [#1839](https://github.com/rails-api/active_model_serializers/pull/1839) `fields` tests demonstrating usage for both attributes and relationships. (@NullVoxPopuli)
 - [#1812](https://github.com/rails-api/active_model_serializers/pull/1812) add a code of conduct (@corainchicago)
 

docs/ARCHITECTURE.md

@@ -15,7 +15,7 @@ It requires an adapter to transform its attributes into a JSON document; it cann
 It may be useful to think of it as a
 [presenter](http://blog.steveklabnik.com/posts/2011-09-09-better-ruby-presenters).
 
-The **`ActiveModel::ArraySerializer`** represent a collection of resources as serializers
+The **`ActiveModel::CollectionSerializer`** represents a collection of resources as serializers
 and, if there is no serializer, primitives.
 
 The **`ActiveModel::Adapter`** describes the structure of the JSON document generated from a
@@ -42,10 +42,9 @@ it is not modified.
 Internally, if no serializer can be found in the controller, the resource is not decorated by
 ActiveModelSerializers.
 
-If the collection serializer (ArraySerializer) cannot
+If the collection serializer (CollectionSerializer) cannot
-identify a serializer for a resource in its collection, it raises [`NoSerializerError`](https://github.com/rails-api/active_model_serializers/issues/1191#issuecomment-142327128)
+identify a serializer for a resource in its collection, it throws [`:no_serializer`](https://github.com/rails-api/active_model_serializers/issues/1191#issuecomment-142327128).
-which is rescued in `ActiveModel::Serializer::Reflection#build_association` which sets
+For example, when caught by `Reflection#build_association`, the association value is set directly:
-the association value directly:
 
 ```ruby
 reflection_options[:virtual_value] = association_value.try(:as_json) || association_value
@@ -85,8 +84,8 @@ Details:
   1. The serializer and adapter are created as
     1. `serializer_instance = serializer.new(resource, serializer_opts)`
     2. `adapter_instance = ActiveModel::Serializer::Adapter.create(serializer_instance, adapter_opts)`
-1. **ActiveModel::Serializer::ArraySerializer#new**
+1. **ActiveModel::Serializer::CollectionSerializer#new**
-  1. If the `serializer_instance` was a `ArraySerializer` and the `:serializer` serializer_opts
+  1. If the `serializer_instance` was a `CollectionSerializer` and the `:serializer` serializer_opts
     is present, then [that serializer is passed into each resource](https://github.com/rails-api/active_model_serializers/blob/a54d237e2828fe6bab1ea5dfe6360d4ecc8214cd/lib/active_model/serializer/array_serializer.rb#L14-L16).
 1. **ActiveModel::Serializer#attributes** is used by the adapter to get the attributes for
   resource as defined by the serializer.

lib/active_model/serializer/collection_serializer.rb

@@ -1,7 +1,6 @@
 module ActiveModel
   class Serializer
     class CollectionSerializer
-      NoSerializerError = Class.new(StandardError)
       include Enumerable
       delegate :each, to: :@serializers
 
@@ -74,8 +73,9 @@ module ActiveModel
       def serializer_from_resource(resource, serializer_context_class, options)
         serializer_class = options.fetch(:serializer) { serializer_context_class.serializer_for(resource) }
 
-        if serializer_class.nil? # rubocop:disable Style/GuardClause
+        if serializer_class.nil?
-          fail NoSerializerError, "No serializer found for resource: #{resource.inspect}"
+          ActiveModelSerializers.logger.debug "No serializer found for resource: #{resource.inspect}"
+          throw :no_serializer
         else
           serializer_class.new(resource, options.except(:serializer))
         end

lib/active_model/serializer/reflection.rb

@@ -105,21 +105,24 @@ module ActiveModel
       # @api private
       #
       def build_association(parent_serializer, parent_serializer_options, include_slice = {})
-        association_value = value(parent_serializer, include_slice)
         reflection_options = options.dup
+        association_value = value(parent_serializer, include_slice)
         serializer_class = parent_serializer.class.serializer_for(association_value, reflection_options)
         reflection_options[:include_data] = include_data?(include_slice)
         reflection_options[:links] = @_links
         reflection_options[:meta] = @_meta
 
         if serializer_class
-          begin
+          serializer = catch(:no_serializer) do
-            reflection_options[:serializer] = serializer_class.new(
+            serializer_class.new(
               association_value,
               serializer_options(parent_serializer, parent_serializer_options, reflection_options)
             )
-          rescue ActiveModel::Serializer::CollectionSerializer::NoSerializerError
+          end
+          if serializer.nil?
             reflection_options[:virtual_value] = association_value.try(:as_json) || association_value
+          else
+            reflection_options[:serializer] = serializer
           end
         elsif !association_value.nil? && !association_value.instance_of?(Object)
           reflection_options[:virtual_value] = association_value

lib/active_model_serializers/serializable_resource.rb

@@ -38,9 +38,10 @@ module ActiveModelSerializers
 
     def find_adapter
       return resource unless serializer?
-      ActiveModelSerializers::Adapter.create(serializer_instance, adapter_opts)
+      adapter = catch :no_serializer do
-    rescue ActiveModel::Serializer::CollectionSerializer::NoSerializerError
+        ActiveModelSerializers::Adapter.create(serializer_instance, adapter_opts)
-      resource
+      end
+      adapter || resource
     end
 
     def serializer_instance