Don't autosave unchanged has_one through records

3 files changed, 31 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 40eb32c059..be6d65a721 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Don't autosave unchanged has_one through records
+
+    *Alan Kennedy*, *Steve Parrington*
+
 *   When a thread is killed, rollback the active transaction, instead of
     committing it during the stack unwind. Previously, we could commit half-
     completed work. This fix only works for Ruby 2.0+; on 1.9, we can't
diff --git a/activerecord/lib/active_record/autosave_association.rb b/activerecord/lib/active_record/autosave_association.rb
index a8e4d25df2..2a5dd758a3 100644
--- a/activerecord/lib/active_record/autosave_association.rb
+++ b/activerecord/lib/active_record/autosave_association.rb
@@ -403,7 +403,9 @@ module ActiveRecord
 
       # If the record is new or it has changed, returns true.
       def record_changed?(reflection, record, key)
-        record.new_record? || record[reflection.foreign_key] != key || record.attribute_changed?(reflection.foreign_key)
+        record.new_record? ||
+          (record.attributes.keys.include?(reflection.foreign_key) && record[reflection.foreign_key] != key) ||
+          record.attribute_changed?(reflection.foreign_key)
       end
 
       # Saves the associated record if it's new or <tt>:autosave</tt> is enabled.
diff --git a/activerecord/test/cases/autosave_association_test.rb b/activerecord/test/cases/autosave_association_test.rb
index 025cdbeba9..b2a7d3956d 100644
--- a/activerecord/test/cases/autosave_association_test.rb
+++ b/activerecord/test/cases/autosave_association_test.rb
@@ -19,6 +19,9 @@ require 'models/treasure'
 require 'models/eye'
 require 'models/electron'
 require 'models/molecule'
+require 'models/member'
+require 'models/member_detail'
+require 'models/organization'
 
 class TestAutosaveAssociationsInGeneral < ActiveRecord::TestCase
   def test_autosave_validation
@@ -1116,6 +1119,27 @@ class TestAutosaveAssociationOnAHasOneAssociation < ActiveRecord::TestCase
   end
 end
 
+class TestAutosaveAssociationOnAHasOneThroughAssociation < ActiveRecord::TestCase
+  self.use_transactional_fixtures = false unless supports_savepoints?
+
+  def setup
+    super
+    organization = Organization.create
+    @member = Member.create
+    MemberDetail.create(organization: organization, member: @member)
+  end
+
+  def test_should_not_has_one_through_model
+    class << @member.organization
+      def save(*args)
+        super
+        raise 'Oh noes!'
+      end
+    end
+    assert_nothing_raised { @member.save }
+  end
+end
+
 class TestAutosaveAssociationOnABelongsToAssociation < ActiveRecord::TestCase
   self.use_transactional_fixtures = false unless supports_savepoints?