Fixes touch_with_version re: the :on option

Fixes a bug where e.g. `on: [:create, :destroy]` (not :update)
failed to create a version.

lib/paper_trail/has_paper_trail.rb

@@ -266,8 +266,9 @@ module PaperTrail
         PaperTrail.whodunnit = current_whodunnit
       end
 
-      # Mimicks behavior of `touch` method from `ActiveRecord::Persistence`,
-      # but generates a version
+      # Mimics the `touch` method from `ActiveRecord::Persistence`, but also
+      # creates a version. A version is created regardless of options such as
+      # `:on`, `:if`, or `:unless`.
       #
       # TODO: look into leveraging the `after_touch` callback from
       # `ActiveRecord` to allow the regular `touch` method go generate a version
@@ -281,13 +282,20 @@ module PaperTrail
         current_time = current_time_from_proper_timezone
 
         attributes.each { |column| write_attribute(column, current_time) }
-        # ensure a version is written even if the `:on` collection is empty
-        record_update(true) if paper_trail_options[:on] == []
+
+        record_update(true) unless will_record_after_update?
         save!(:validate => false)
       end
 
       private
 
+      # Returns true if `save` will cause `record_update`
+      # to be called via the `after_update` callback.
+      def will_record_after_update?
+        on = paper_trail_options[:on]
+        on.nil? || on.include?(:update)
+      end
+
       def source_version
         send self.class.version_association_name
       end

spec/models/not_on_update_spec.rb

@@ -0,0 +1,19 @@
+require 'rails_helper'
+
+describe NotOnUpdate, :type => :model do
+  describe "#touch_with_version", :versioning => true do
+    let!(:record) { described_class.create! }
+
+    it "should create a version, regardless" do
+      expect { record.touch_with_version }.to change {
+        PaperTrail::Version.count
+      }.by(+1)
+    end
+
+    it "increments the `:updated_at` timestamp" do
+      before = record.updated_at
+      record.touch_with_version
+      expect(record.updated_at).to be > before
+    end
+  end
+end

spec/models/widget_spec.rb

@@ -252,13 +252,13 @@ describe Widget, :type => :model do
       describe '#touch_with_version' do
         it { is_expected.to respond_to(:touch_with_version) }
 
-        it "should generate a version" do
+        it "creates a version" do
           count = widget.versions.size
           widget.touch_with_version
           expect(widget.versions.size).to eq(count + 1)
         end
 
-        it "should increment the `:updated_at` timestamp" do
+        it "increments the `:updated_at` timestamp" do
           time_was = widget.updated_at
           widget.touch_with_version
           expect(widget.updated_at).to be > time_was

test/dummy/app/models/not_on_update.rb

@@ -0,0 +1,4 @@
+# This model does not record versions when updated.
+class NotOnUpdate < ActiveRecord::Base
+  has_paper_trail :on => [:create, :destroy]
+end

test/dummy/db/migrate/20110208155312_set_up_test_tables.rb

@@ -73,6 +73,10 @@ class SetUpTestTables < ActiveRecord::Migration
       add_index :json_versions, [:item_type, :item_id]
     end
 
+    create_table :not_on_updates, :force => true do |t|
+      t.timestamps :null => true
+    end
+
     create_table :bananas, :force => true do |t|
       t.timestamps :null => true
     end
@@ -205,6 +209,7 @@ class SetUpTestTables < ActiveRecord::Migration
 
   def self.down
     drop_table :animals
+    drop_table :not_on_updates
     drop_table :posts
     drop_table :songs
     drop_table :editors