Fix stale_state for nested has_many :through associations

Need reloading when through record has replaced.

activerecord/lib/active_record/associations/through_association.rb

@@ -4,9 +4,20 @@ module ActiveRecord
   module Associations
     # = Active Record Through Association
     module ThroughAssociation #:nodoc:
-      delegate :source_reflection, :through_reflection, to: :reflection
+      delegate :source_reflection, to: :reflection
 
       private
+        def through_reflection
+          @through_reflection ||= begin
+            refl = reflection.through_reflection
+
+            while refl.through_reflection?
+              refl = refl.through_reflection
+            end
+
+            refl
+          end
+        end
 
         # We merge in these scopes for two reasons:
         #
@@ -68,7 +79,7 @@ module ActiveRecord
         end
 
         def foreign_key_present?
-          through_reflection.belongs_to_or_through? && !owner[through_reflection.foreign_key].nil?
+          through_reflection.belongs_to? && !owner[through_reflection.foreign_key].nil?
         end
 
         def ensure_mutable

activerecord/lib/active_record/reflection.rb

@@ -504,10 +504,6 @@ module ActiveRecord
         @association_scope_cache.clear
       end
 
-      def belongs_to_or_through?
-        belongs_to?
-      end
-
       def nested?
         false
       end
@@ -840,10 +836,6 @@ module ActiveRecord
         source_reflection.join_scopes(table, predicate_builder) + super
       end
 
-      def belongs_to_or_through?
-        through_reflection.belongs_to_or_through?
-      end
-
       def has_scope?
         scope || options[:source_type] ||
           source_reflection.has_scope? ||

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -1314,12 +1314,20 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
       has_many :subscriptions, through: :author
     end
     post = post_with_single_has_many_through.new
-    post.author = Author.create!(name: "Federico Morissette")
-    book = Book.create!(name: "essays on single has many through associations")
-    post.author.books << book
-    subscription = Subscription.first
-    book.subscriptions << subscription
-    assert_equal [subscription], post.subscriptions.to_a
+
+    post.author = authors(:mary)
+    book1 = Book.create!(name: "essays on single has many through associations 1")
+    post.author.books << book1
+    subscription1 = Subscription.first
+    book1.subscriptions << subscription1
+    assert_equal [subscription1], post.subscriptions.to_a
+
+    post.author = authors(:bob)
+    book2 = Book.create!(name: "essays on single has many through associations 2")
+    post.author.books << book2
+    subscription2 = Subscription.second
+    book2.subscriptions << subscription2
+    assert_equal [subscription2], post.subscriptions.to_a
   end
 
   def test_nested_has_many_through_association_with_unpersisted_parent_instance
@@ -1329,12 +1337,20 @@ class HasManyThroughAssociationsTest < ActiveRecord::TestCase
       has_many :subscriptions, through: :books
     end
     post = post_with_nested_has_many_through.new
-    post.author = Author.create!(name: "Obie Weissnat")
-    book = Book.create!(name: "essays on nested has many through associations")
-    post.author.books << book
-    subscription = Subscription.first
-    book.subscriptions << subscription
-    assert_equal [subscription], post.subscriptions.to_a
+
+    post.author = authors(:mary)
+    book1 = Book.create!(name: "essays on nested has many through associations 1")
+    post.author.books << book1
+    subscription1 = Subscription.first
+    book1.subscriptions << subscription1
+    assert_equal [subscription1], post.subscriptions.to_a
+
+    post.author = authors(:bob)
+    book2 = Book.create!(name: "essays on nested has many through associations 2")
+    post.author.books << book2
+    subscription2 = Subscription.second
+    book2.subscriptions << subscription2
+    assert_equal [subscription2], post.subscriptions.to_a
   end
 
   private