add #no_touching on ActiveRecord models

2 files changed, 53 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 69a9eabefb..e05e22ebb0 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -295,6 +295,7 @@ module ActiveRecord #:nodoc:
     extend Delegation::DelegateCache
 
     include Persistence
+    include NoTouching
     include ReadonlyAttributes
     include ModelSchema
     include Inheritance
diff --git a/activerecord/lib/active_record/no_touching.rb b/activerecord/lib/active_record/no_touching.rb
new file mode 100644
index 0000000000..dbf4564ae5
--- /dev/null
+++ b/activerecord/lib/active_record/no_touching.rb
@@ -0,0 +1,52 @@
+module ActiveRecord
+  # = Active Record No Touching
+  module NoTouching
+    extend ActiveSupport::Concern
+
+    module ClassMethods
+      # Lets you selectively disable calls to `touch` for the
+      # duration of a block.
+      #
+      # ==== Examples
+      #   ActiveRecord::Base.no_touching do
+      #     Project.first.touch  # does nothing
+      #     Message.first.touch  # does nothing
+      #   end
+      #
+      #   Project.no_touching do
+      #     Project.first.touch  # does nothing
+      #     Message.first.touch  # works, but does not touch the associated project
+      #   end
+      #
+      def no_touching(&block)
+        NoTouching.apply_to(self, &block)
+      end
+    end
+
+    class << self
+      def apply_to(klass) #:nodoc:
+        klasses.push(klass)
+        yield
+      ensure
+        klasses.pop
+      end
+
+      def applied_to?(klass) #:nodoc:
+        klasses.any? { |k| k >= klass }
+      end
+
+      private
+        def klasses
+          Thread.current[:no_touching_classes] ||= []
+        end
+    end
+
+    def no_touching?
+      NoTouching.applied_to?(self.class)
+    end
+
+    def touch(*)
+      super unless no_touching?
+    end
+  end
+end