This adds namespace lookup to serializer_for (#1968)

* This adds namespace lookup to serializer_for

* address rubocop issue

* address @bf4's feedback

* add docs

* update docs, add more tests

* apparently rails master doesn't have before filter

* try to address serializer cache issue between tests

* update cache for serializer lookup to include namespace in the key, and fix the tests for explicit namespace

* update docs, and use better cache key creation method

* update docs [ci skip]

* update docs [ci skip]

* add to changelog [ci skip]

lib/action_controller/serialization.rb

@@ -16,6 +16,12 @@ module ActionController
     included do
       class_attribute :_serialization_scope
       self._serialization_scope = :current_user
+
+      attr_writer :namespace_for_serializer
+    end
+
+    def namespace_for_serializer
+      @namespace_for_serializer ||= self.class.parent unless self.class.parent == Object
     end
 
     def serialization_scope
@@ -30,6 +36,9 @@ module ActionController
           "Please pass 'adapter: false' or see ActiveSupport::SerializableResource.new"
         options[:adapter] = false
       end
+
+      options.fetch(:namespace) { options[:namespace] = namespace_for_serializer }
+
       serializable_resource = ActiveModelSerializers::SerializableResource.new(resource, options)
       serializable_resource.serialization_scope ||= options.fetch(:scope) { serialization_scope }
       serializable_resource.serialization_scope_name = options.fetch(:scope_name) { _serialization_scope }

lib/active_model/serializer.rb

@@ -44,7 +44,7 @@ module ActiveModel
       elsif resource.respond_to?(:to_ary)
         config.collection_serializer
       else
-        options.fetch(:serializer) { get_serializer_for(resource.class) }
+        options.fetch(:serializer) { get_serializer_for(resource.class, options[:namespace]) }
       end
     end
 
@@ -59,13 +59,14 @@ module ActiveModel
     end
 
     # @api private
-    def self.serializer_lookup_chain_for(klass)
+    def self.serializer_lookup_chain_for(klass, namespace = nil)
       chain = []
 
       resource_class_name = klass.name.demodulize
       resource_namespace = klass.name.deconstantize
       serializer_class_name = "#{resource_class_name}Serializer"
 
+      chain.push("#{namespace}::#{serializer_class_name}") if namespace
       chain.push("#{name}::#{serializer_class_name}") if self != ActiveModel::Serializer
       chain.push("#{resource_namespace}::#{serializer_class_name}")
 
@@ -84,11 +85,14 @@ module ActiveModel
     #   1. class name appended with "Serializer"
     #   2. try again with superclass, if present
     #   3. nil
-    def self.get_serializer_for(klass)
+    def self.get_serializer_for(klass, namespace = nil)
       return nil unless config.serializer_lookup_enabled
-      serializers_cache.fetch_or_store(klass) do
+
+      cache_key = ActiveSupport::Cache.expand_cache_key(klass, namespace)
+      serializers_cache.fetch_or_store(cache_key) do
         # NOTE(beauby): When we drop 1.9.3 support we can lazify the map for perfs.
-        serializer_class = serializer_lookup_chain_for(klass).map(&:safe_constantize).find { |x| x && x < ActiveModel::Serializer }
+        lookup_chain = serializer_lookup_chain_for(klass, namespace)
+        serializer_class = lookup_chain.map(&:safe_constantize).find { |x| x && x < ActiveModel::Serializer }
 
         if serializer_class
           serializer_class

lib/active_model/serializer/reflection.rb

@@ -106,6 +106,10 @@ module ActiveModel
       #
       def build_association(parent_serializer, parent_serializer_options, include_slice = {})
         reflection_options = options.dup
+
+        # Pass the parent's namespace onto the child serializer
+        reflection_options[:namespace] ||= parent_serializer_options[:namespace]
+
         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)

lib/active_model_serializers/serializable_resource.rb

@@ -55,7 +55,7 @@ module ActiveModelSerializers
       @serializer ||=
         begin
           @serializer = serializer_opts.delete(:serializer)
-          @serializer ||= ActiveModel::Serializer.serializer_for(resource)
+          @serializer ||= ActiveModel::Serializer.serializer_for(resource, serializer_opts)
 
           if serializer_opts.key?(:each_serializer)
             serializer_opts[:serializer] = serializer_opts.delete(:each_serializer)