has_paper_trail ":ignore_if" parameter

README.md

@@ -179,6 +179,15 @@ You can choose which events to track with the `on` option.  For example, to igno
     end
 
 
+## Choosing When Not To Save New Versions
+
+You can choose the condition when not to add new versions with the `ignore_if` option. For example, to ignore non-US translations:
+
+    class Translation < ActiveRecord::Base
+      has_paper_trail :ignore_if => Proc.new { |t| t.language_code != 'US' }
+    end
+
+
 
 ## Choosing Attributes To Monitor
 

lib/paper_trail/has_paper_trail.rb

@@ -43,6 +43,9 @@ module PaperTrail
         class_attribute :ignore
         self.ignore = ([options[:ignore]].flatten.compact || []).map &:to_s
 
+        class_attribute :ignore_condition
+        self.ignore_condition = options[:ignore_if]
+
         class_attribute :skip
         self.skip = ([options[:skip]].flatten.compact || []).map &:to_s
 
@@ -124,6 +127,10 @@ module PaperTrail
         self.class.paper_trail_on if paper_trail_was_enabled
       end
 
+      def prevent_versioning?
+        ignore_condition && ignore_condition.call(self)
+      end
+
       private
 
       def version_class
@@ -135,13 +142,13 @@ module PaperTrail
       end
 
       def record_create
-        if switched_on?
+        if switched_on? && !prevent_versioning?
           send(self.class.versions_association_name).create merge_metadata(:event => 'create', :whodunnit => PaperTrail.whodunnit)
         end
       end
 
       def record_update
-        if switched_on? && changed_notably?
+        if switched_on? && changed_notably? && !prevent_versioning?
           data = {
             :event     => 'update',
             :object    => object_to_string(item_before_change),

test/dummy/app/models/translation.rb

@@ -0,0 +1,3 @@
+class Translation < ActiveRecord::Base
+  has_paper_trail :ignore_if => Proc.new { |t| t.language_code != 'US' }
+end

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

@@ -103,7 +103,12 @@ class SetUpTestTables < ActiveRecord::Migration
       t.string    :name
       t.integer   :version
     end
-  
+
+    create_table :translations, :force => true do |t|
+      t.string    :headline
+      t.string    :content
+      t.string    :language_code
+    end
   end
 
   def self.down
@@ -123,5 +128,6 @@ class SetUpTestTables < ActiveRecord::Migration
     drop_table :widgets
     drop_table :documents
     drop_table :legacy_widgets
+    drop_table :translations
   end
 end

test/unit/model_test.rb

@@ -68,6 +68,32 @@ class HasPaperTrailModelTest < ActiveSupport::TestCase
     end
   end
 
+  context 'A record with defined "ignore_if" attribute' do
+    setup { @translation = Translation.new :headline => 'Headline' }
+
+    context 'for non-US translations' do
+      setup { @translation.save }
+      should_not_change('the number of versions') { Version.count }
+
+      context 'after update' do
+        setup { @translation.update_attributes :content => 'Content' }
+        should_not_change('the number of versions') { Version.count }
+      end
+    end
+
+    context 'for US translations' do
+      setup do
+        @translation.language_code = "US"
+        @translation.save
+      end
+      should_change('the number of versions', :by => 1) { Version.count }
+
+      context 'after update' do
+        setup { @translation.update_attributes :content => 'Content' }
+        should_change('the number of versions', :by => 1) { Version.count }
+      end
+    end
+  end
 
   context 'A new record' do
     setup { @widget = Widget.new }