Fix for HABTM associations when updated within 1 transaction

When updating 2 models with a HABTM association, and using
accepts_nested_attributes_for, the association was using the
version ID instead of the transaction ID to reference the change.
This was braking the association logic and preventing proper
reification.

CHANGELOG.md

@@ -11,6 +11,8 @@
 
 ### Fixed
 
+- [#812](https://github.com/airblade/paper_trail/pull/812) -
+  Issue with saving HABTM associated objects using accepts_nested_attributes_for
 - Improvements to documentation
 
 ## 5.0.1 (2016-05-04)

lib/paper_trail/has_paper_trail.rb

@@ -535,7 +535,7 @@ module PaperTrail
             self.class.paper_trail_save_join_tables.include?(a.name) ||
                 a.klass.paper_trail_enabled_for_model?
           assoc_version_args = {
-            version_id: version.id,
+            version_id: version.transaction_id,
             foreign_key_name: a.name
           }
           assoc_ids =

test/dummy/app/models/foo_habtm.rb

@@ -1,4 +1,5 @@
 class FooHabtm < ActiveRecord::Base
   has_and_belongs_to_many :bar_habtms
+  accepts_nested_attributes_for :bar_habtms
   has_paper_trail
 end

test/unit/associations_test.rb

@@ -988,5 +988,29 @@ class AssociationsTest < ActiveSupport::TestCase
         end
       end
     end
+
+    context "updated via nested attributes" do
+      setup do
+        @foo = FooHabtm.create(
+          name: "foo",
+          bar_habtms_attributes: [{ name: "bar" }]
+        )
+        Timecop.travel 1.second.since
+        @foo.update_attributes(
+          name: "foo2",
+          bar_habtms_attributes: [{ id: @foo.bar_habtms.first.id, name: "bar2" }]
+        )
+
+        @reified = @foo.versions.last.reify(has_and_belongs_to_many: true)
+      end
+
+      should "see the associated object as it was at the time" do
+        assert_equal "bar", @reified.bar_habtms.first.name
+      end
+
+      should "not persist changes to the live object" do
+        assert_not_equal @reified.bar_habtms.first.name, @foo.reload.bar_habtms.first.name
+      end
+    end
   end
 end