Fix issue evaluating polymorphic joins

polyamorous/lib/polyamorous.rb

@@ -16,7 +16,10 @@ module Polyamorous
     require "polyamorous/activerecord_#{ar_version}_ruby_2/#{file}"
   end
 
-  ActiveRecord::Reflection::AbstractReflection.send(:prepend, Polyamorous::ReflectionExtensions)
+  if ar_version >= "6.0.0"
+    require "polyamorous/activerecord_#{ar_version}_ruby_2/reflection.rb"
+    ::ActiveRecord::Reflection::AbstractReflection.send(:prepend, Polyamorous::ReflectionExtensions)
+  end
 
   Polyamorous::JoinDependency.send(:prepend, Polyamorous::JoinDependencyExtensions)
   Polyamorous::JoinDependency.singleton_class.send(:prepend, Polyamorous::JoinDependencyExtensions::ClassMethods)

spec/ransack/search_spec.rb

@@ -284,6 +284,14 @@ module Ransack
         expect(s.to_sql).to match /#{people_name_field} = 'Ernie'/
       end
 
+      it "evaluates polymorphic joins" do
+        s = Search.new(Person, article_notes_id_in: [1,2,3]).result
+        expect(s).to be_an ActiveRecord::Relation
+
+        notes_id_field = "#{quote_table_name("notes")}.#{quote_column_name("id")}"
+        expect(s.to_sql).to match /#{notes_id_field} IN \(1, 2, 3\)/
+      end
+
       it 'evaluates nested conditions' do
         s = Search.new(Person, children_name_eq: 'Ernie',
           g: [

spec/support/schema.rb

@@ -37,6 +37,7 @@ class Person < ActiveRecord::Base
   has_many   :authored_article_comments, through: :articles,
              source: :comments, foreign_key: :person_id
   has_many   :notes, as: :notable
+  has_many   :article_notes, through: :articles, source: :item, source_type: "Note"
 
   scope :restricted,  lambda { where("restricted = 1") }
   scope :active,      lambda { where("active = 1") }
@@ -132,6 +133,7 @@ class Article < ActiveRecord::Base
   has_many :comments
   has_and_belongs_to_many :tags
   has_many :notes, as: :notable
+  belongs_to :item, polymorphic: true
 
   alias_attribute :content, :body