If a has_many goes :through a belongs_to, and the foreign key of the belongs_to changes, then the has_many should be considered stale.

5 files changed, 31 insertions, 3 deletions

diff --git a/activerecord/lib/active_record/associations/belongs_to_association.rb b/activerecord/lib/active_record/associations/belongs_to_association.rb
index c9abfe36e8..bbfe18f9fb 100644
--- a/activerecord/lib/active_record/associations/belongs_to_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_association.rb
@@ -44,7 +44,10 @@ module ActiveRecord
 
       def stale_target?
         if @target && @target.persisted?
-          @target.send(@reflection.association_primary_key).to_i != @owner.send(@reflection.primary_key_name).to_i
+          target_id   = @target.send(@reflection.association_primary_key).to_s
+          foreign_key = @owner.send(@reflection.primary_key_name).to_s
+
+          target_id != foreign_key
         else
           false
         end
diff --git a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
index 844ae94c3d..c580de7fbe 100644
--- a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
@@ -25,8 +25,12 @@ module ActiveRecord
 
       def stale_target?
         if @target && @target.persisted?
-          @target.send(@reflection.association_primary_key).to_i != @owner.send(@reflection.primary_key_name).to_i ||
-          @target.class.base_class.name.to_s != @owner.send(@reflection.options[:foreign_type]).to_s
+          target_id    = @target.send(@reflection.association_primary_key).to_s
+          foreign_key  = @owner.send(@reflection.primary_key_name).to_s
+          target_type  = @target.class.base_class.name
+          foreign_type = @owner.send(@reflection.options[:foreign_type]).to_s
+
+          target_id != foreign_key || target_type != foreign_type
         else
           false
         end
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index f0bc6aedf2..5f4667b4d8 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -59,6 +59,7 @@ module ActiveRecord
 
         def find_target
           return [] unless target_reflection_has_associated_record?
+          update_stale_state
           scoped.all
         end
 
diff --git a/activerecord/lib/active_record/associations/has_one_through_association.rb b/activerecord/lib/active_record/associations/has_one_through_association.rb
index e8cf73976b..eb17935d6a 100644
--- a/activerecord/lib/active_record/associations/has_one_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_through_association.rb
@@ -33,6 +33,7 @@ module ActiveRecord
 
     private
       def find_target
+        update_stale_state
         scoped.first
       end
     end
diff --git a/activerecord/lib/active_record/associations/through_association_scope.rb b/activerecord/lib/active_record/associations/through_association_scope.rb
index c11fce5db0..e57de84f66 100644
--- a/activerecord/lib/active_record/associations/through_association_scope.rb
+++ b/activerecord/lib/active_record/associations/through_association_scope.rb
@@ -10,6 +10,17 @@ module ActiveRecord
         end
       end
 
+      def stale_target?
+        if @target && @reflection.through_reflection.macro == :belongs_to && defined?(@through_foreign_key)
+          previous_key = @through_foreign_key.to_s
+          current_key  = @owner.send(@reflection.through_reflection.primary_key_name).to_s
+
+          previous_key != current_key
+        else
+          false
+        end
+      end
+
       protected
 
       def construct_find_scope
@@ -165,6 +176,14 @@ module ActiveRecord
       end
 
       alias_method :sql_conditions, :conditions
+
+      def update_stale_state
+        construct_scope if stale_target?
+
+        if @reflection.through_reflection.macro == :belongs_to
+          @through_foreign_key = @owner.send(@reflection.through_reflection.primary_key_name)
+        end
+      end
     end
   end
 end