Move constructing polymorphic type to `join_scope` in `Reflection`

3 files changed, 10 insertions, 16 deletions

diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index 95f16c622e..70520b8e85 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -40,21 +40,13 @@ module ActiveRecord
 
             constraint = build_constraint(klass, table, key, foreign_table, foreign_key)
 
-            rel = reflection.join_scope(table)
+            rel = reflection.join_scope(table, foreign_klass)
 
-            if rel && !rel.arel.constraints.empty?
+            if rel.arel.constraints.any?
               binds += rel.bound_attributes
               constraint = constraint.and rel.arel.constraints
             end
 
-            if reflection.type
-              value = foreign_klass.base_class.name
-              column = klass.columns_hash[reflection.type.to_s]
-
-              binds << Relation::QueryAttribute.new(column.name, value, klass.type_for_attribute(column.name))
-              constraint = constraint.and klass.arel_attribute(reflection.type, table).eq(Arel::Nodes::BindParam.new)
-            end
-
             joins << table.create_join(table, table.create_on(constraint), join_type)
 
             # The current table in this iteration becomes the foreign table in the next
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index c6aa2ed720..4e3359bb4e 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -185,12 +185,16 @@ module ActiveRecord
       end
       deprecate :scope_chain
 
-      def join_scope(table)
+      def join_scope(table, foreign_klass)
         predicate_builder = predicate_builder(table)
         scope_chain_items = join_scopes(table, predicate_builder)
         klass_scope       = klass_join_scope(table, predicate_builder)
 
-        scope_chain_items.inject(klass_scope || scope_chain_items.shift, &:merge!)
+        if type
+          klass_scope.where!(type => foreign_klass.base_class.name)
+        end
+
+        scope_chain_items.inject(klass_scope, &:merge!)
       end
 
       def join_scopes(table, predicate_builder) # :nodoc:
@@ -207,8 +211,7 @@ module ActiveRecord
             scope.joins_values = scope.left_outer_joins_values = [].freeze
           }
         else
-          relation = build_scope(table, predicate_builder)
-          klass.send(:build_default_scope, relation)
+          klass.default_scoped(build_scope(table, predicate_builder))
         end
       end
 
diff --git a/activerecord/lib/active_record/scoping/named.rb b/activerecord/lib/active_record/scoping/named.rb
index a61fdd6454..388f471bf5 100644
--- a/activerecord/lib/active_record/scoping/named.rb
+++ b/activerecord/lib/active_record/scoping/named.rb
@@ -29,8 +29,7 @@ module ActiveRecord
           end
         end
 
-        def default_scoped # :nodoc:
-          scope = relation
+        def default_scoped(scope = relation) # :nodoc:
           build_default_scope(scope) || scope
         end