fix: more flexible polymorphic types lookup

lib/jsonapi/relationship.rb

@@ -193,7 +193,7 @@ def polymorphic_type
       def setup_implicit_relationships_for_polymorphic_types(exclude_linkage_data: true)
         types = self.class.polymorphic_types(_relation_name)
         unless types.present?
-          warn "No polymorphic types found for #{parent_resource.name} #{_relation_name}"
+          warn "[POLYMORPHIC TYPE] No polymorphic types found for #{parent_resource.name} #{_relation_name}"
           return
         end
 

lib/jsonapi/resources/railtie.rb

@@ -18,6 +18,10 @@ class Railtie < ::Rails::Railtie
             ::JSONAPI::MimeTypes.parser.call(body)
           }
       end
+
+      initializer "jsonapi_resources.initialize", after: :initialize do
+        JSONAPI::Utils::PolymorphicTypesLookup.polymorphic_types_lookup_clear!
+      end
     end
   end
 end

lib/jsonapi/utils/polymorphic_types_lookup.rb

@@ -5,26 +5,79 @@ module Utils
     module PolymorphicTypesLookup
       extend self
 
-      def polymorphic_types(name)
-        polymorphic_types_lookup[name.to_sym]
+      singleton_class.attr_accessor :build_polymorphic_types_lookup_strategy
+      self.build_polymorphic_types_lookup_strategy =
+        :build_polymorphic_types_lookup_from_object_space
+
+      def polymorphic_types(name, rebuild: false)
+        polymorphic_types_lookup(rebuild: rebuild).fetch(name.to_sym, &handle_polymorphic_type_name_found)
+      end
+
+      def handle_polymorphic_type_name_found
+        @handle_polymorphic_type_name_found ||= lambda do |name|
+          warn "[POLYMORPHIC TYPE NOT FOUND] No polymorphic types found for #{name}"
+          nil
+        end
       end
 
-      def polymorphic_types_lookup
+      def polymorphic_types_lookup(rebuild: false)
+        polymorphic_types_lookup_clear! if rebuild
         @polymorphic_types_lookup ||= build_polymorphic_types_lookup
       end
 
+      def polymorphic_types_lookup_clear!
+        @polymorphic_types_lookup = nil
+      end
+
       def build_polymorphic_types_lookup
-        {}.tap do |hash|
+        public_send(build_polymorphic_types_lookup_strategy)
+      end
+
+      def build_polymorphic_types_lookup_from_descendants
+        {}.tap do |lookup|
+          ActiveRecord::Base
+            .descendants
+            .select(&:name)
+            .reject(&:abstract_class)
+            .select(&:model_name).map {|klass|
+              add_polymorphic_types_lookup(klass: klass, lookup: lookup)
+            }
+        end
+      end
+
+      def build_polymorphic_types_lookup_from_object_space
+        {}.tap do |lookup|
           ObjectSpace.each_object do |klass|
             next unless Module === klass
-            if ActiveRecord::Base > klass
-              klass.reflect_on_all_associations(:has_many).select { |r| r.options[:as] }.each do |reflection|
-                (hash[reflection.options[:as]] ||= []) << klass.name.underscore
-              end
-            end
+            next unless ActiveRecord::Base > klass
+            add_polymorphic_types_lookup(klass: klass, lookup: lookup)
           end
         end
       end
+
+      # TODO(BF): Consider adding the following conditions
+      # is_active_record_inspectable = true
+      # is_active_record_inspectable &&= klass.respond_to?(:reflect_on_all_associations, true)
+      # is_active_record_inspectable &&= format_polymorphic_klass_type(klass).present?
+      # return unless is_active_record_inspectable
+      def add_polymorphic_types_lookup(klass:, lookup:)
+        klass.reflect_on_all_associations(:has_many).select { |r| r.options[:as] }.each do |reflection|
+          (lookup[reflection.options[:as]] ||= []) << format_polymorphic_klass_type(klass).underscore
+        end
+      end
+
+      # TODO(BF): Consider adding the following conditions
+      # klass.name ||
+      #   begin
+      #     klass.model_name.name
+      #   rescue ArgumentError => ex
+      #     # klass.base_class may be nil
+      #     warn "[POLYMORPHIC TYPE] #{__callee__} #{klass} #{ex.inspect}"
+      #     nil
+      #   end
+      def format_polymorphic_klass_type(klass)
+        klass.name
+      end
     end
   end
 end

test/unit/utils/polymorphic_types_lookup_test.rb

@@ -0,0 +1,35 @@
+require File.expand_path('../../../test_helper', __FILE__)
+
+class PolymorphicTypesLookupTest < ActiveSupport::TestCase
+  def setup
+    JSONAPI::Utils::PolymorphicTypesLookup.polymorphic_types_lookup_clear!
+  end
+
+  def test_build_polymorphic_types_lookup_from_object_space
+    expected = {
+      :imageable=>["product", "document"]
+    }
+    actual = JSONAPI::Utils::PolymorphicTypesLookup.build_polymorphic_types_lookup_from_object_space
+    actual_keys = actual.keys.sort
+    assert_equal(actual_keys, expected.keys.sort)
+    actual_keys.each do |actual_key|
+      actual_values = actual[actual_key].sort
+      expected_values = expected[actual_key].sort
+      assert_equal(actual_values, expected_values)
+    end
+  end
+
+  def test_build_polymorphic_types_lookup_from_descendants
+    expected = {
+      :imageable=>["document", "product"]
+    }
+    actual = JSONAPI::Utils::PolymorphicTypesLookup.build_polymorphic_types_lookup_from_descendants
+    actual_keys = actual.keys.sort
+    assert_equal(actual_keys, expected.keys.sort)
+    actual_keys.each do |actual_key|
+      actual_values = actual[actual_key].sort
+      expected_values = expected[actual_key].sort
+      assert_equal(actual_values, expected_values)
+    end
+  end
+end