1 files changed, 34 insertions, 14 deletions
diff --git a/activerecord/lib/active_record/associations/through_association.rb b/activerecord/lib/active_record/associations/through_association.rb
index ba7d2a3782..09828dbd9b 100644
--- a/activerecord/lib/active_record/associations/through_association.rb
+++ b/activerecord/lib/active_record/associations/through_association.rb
@@ -3,7 +3,7 @@ module ActiveRecord
   module Associations
     module ThroughAssociation #:nodoc:
 
-      delegate :source_reflection, :through_reflection, :chain, :to => :reflection
+      delegate :source_reflection, :through_reflection, :to => :reflection
 
       protected
 
@@ -13,10 +13,16 @@ module ActiveRecord
         #   2. To get the type conditions for any STI models in the chain
         def target_scope
           scope = super
-          chain.drop(1).each do |reflection|
+          reflection.chain.drop(1).each do |reflection|
+            relation = reflection.klass.all
+
+            reflection_scope = reflection.scope
+            if reflection_scope && reflection_scope.arity.zero?
+              relation.merge!(reflection_scope)
+            end
+
             scope.merge!(
-              reflection.klass.all.
-                except(:select, :create_with, :includes, :preload, :joins, :eager_load)
+              relation.except(:select, :create_with, :includes, :preload, :joins, :eager_load)
             )
           end
           scope
@@ -39,12 +45,16 @@ module ActiveRecord
         def construct_join_attributes(*records)
           ensure_mutable
 
-          join_attributes = {
-            source_reflection.foreign_key =>
-              records.map { |record|
-                record.send(source_reflection.association_primary_key(reflection.klass))
-              }
-          }
+          if source_reflection.association_primary_key(reflection.klass) == reflection.klass.primary_key
+            join_attributes = { source_reflection.name => records }
+          else
+            join_attributes = {
+              source_reflection.foreign_key =>
+                records.map { |record|
+                  record.send(source_reflection.association_primary_key(reflection.klass))
+                }
+            }
+          end
 
           if options[:source_type]
             join_attributes[source_reflection.foreign_type] =
@@ -61,18 +71,17 @@ module ActiveRecord
         # Note: this does not capture all cases, for example it would be crazy to try to
         # properly support stale-checking for nested associations.
         def stale_state
-          if through_reflection.macro == :belongs_to
+          if through_reflection.belongs_to?
             owner[through_reflection.foreign_key] && owner[through_reflection.foreign_key].to_s
           end
         end
 
         def foreign_key_present?
-          through_reflection.macro == :belongs_to &&
-          !owner[through_reflection.foreign_key].nil?
+          through_reflection.belongs_to? && !owner[through_reflection.foreign_key].nil?
         end
 
         def ensure_mutable
-          if source_reflection.macro != :belongs_to
+          unless source_reflection.belongs_to?
             raise HasManyThroughCantAssociateThroughHasOneOrManyReflection.new(owner, reflection)
           end
         end
@@ -82,6 +91,17 @@ module ActiveRecord
             raise HasManyThroughNestedAssociationsAreReadonly.new(owner, reflection)
           end
         end
+
+        def build_record(attributes)
+          inverse = source_reflection.inverse_of
+          target = through_association.target
+
+          if inverse && target && !target.is_a?(Array)
+            attributes[inverse.foreign_key] = target.id
+          end
+
+          super(attributes)
+        end
     end
   end
 end