Merge remote-tracking branch 'kennyj/fix_5563'

Conflicts:
	activerecord/test/cases/associations/belongs_to_associations_test.rb

4 files changed, 6 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
index 4e09a43f8e..e75003f261 100644
--- a/activerecord/lib/active_record/associations/association.rb
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -132,7 +132,8 @@ module ActiveRecord
       # ActiveRecord::RecordNotFound is rescued within the method, and it is
       # not reraised. The proxy is \reset and +nil+ is the return value.
       def load_target
-        @target ||= find_target if find_target?
+        @target = find_target if (@stale_state && stale_target?) || find_target?
+
         loaded! unless loaded?
         target
       rescue ActiveRecord::RecordNotFound
diff --git a/activerecord/lib/active_record/associations/belongs_to_association.rb b/activerecord/lib/active_record/associations/belongs_to_association.rb
index 81c6e400d2..ddfc6f6c05 100644
--- a/activerecord/lib/active_record/associations/belongs_to_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_association.rb
@@ -77,7 +77,7 @@ module ActiveRecord
         end
 
         def stale_state
-          owner[reflection.foreign_key].to_s
+          owner[reflection.foreign_key] && owner[reflection.foreign_key].to_s
         end
     end
   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 2ee5dbbd70..88ce03a3cd 100644
--- a/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
+++ b/activerecord/lib/active_record/associations/belongs_to_polymorphic_association.rb
@@ -27,7 +27,8 @@ module ActiveRecord
         end
 
         def stale_state
-          [super, owner[reflection.foreign_type].to_s]
+          foreign_key = super
+          foreign_key && [foreign_key.to_s, owner[reflection.foreign_type].to_s]
         end
     end
   end
diff --git a/activerecord/lib/active_record/associations/through_association.rb b/activerecord/lib/active_record/associations/through_association.rb
index fd0e90aaf0..be890e5767 100644
--- a/activerecord/lib/active_record/associations/through_association.rb
+++ b/activerecord/lib/active_record/associations/through_association.rb
@@ -62,7 +62,7 @@ module ActiveRecord
         # properly support stale-checking for nested associations.
         def stale_state
           if through_reflection.macro == :belongs_to
-            owner[through_reflection.foreign_key].to_s
+            owner[through_reflection.foreign_key] && owner[through_reflection.foreign_key].to_s
           end
         end