Prevent infinite loops on attribute getter/setter overrides that are mutable.

Author: durran

lib/mongoid/dirty.rb

@@ -108,5 +108,22 @@ def attribute_changed?(attr)
       return false unless changed_attributes.include?(attr)
       changed_attributes[attr] != attributes[attr]
     end
+
+    # Override Active Model's behaviour here in order to stay away from
+    # infinite loops on getter/setter overrides.
+    #
+    # @example Flag an attribute as changing.
+    #   document.attribute_will_change!(:name)
+    #
+    # @param [ Symbol ] attr The attribute.
+    #
+    # @return [ Object ] The value of the attribute.
+    #
+    # @since 2.3.0
+    def attribute_will_change!(attr)
+      value = read_attribute(attr)
+      value = value.duplicable? ? value.clone : value
+      changed_attributes[attr] = value unless changed_attributes.include?(attr)
+    end
   end
 end

spec/app/models/account.rb

@@ -4,6 +4,8 @@ class Account
   field :balance, :type => String
   field :nickname, :type => String
   field :name, :type => String
+
+  field :overridden, :type => String
   key :name
 
   embeds_many :memberships
@@ -17,4 +19,8 @@ class Account
 
   validates_presence_of :name
   validates_length_of :name, :maximum => 10, :on => :create
+
+  def overridden
+    self[:overridden] = "not recommended"
+  end
 end

spec/unit/mongoid/attributes_spec.rb

@@ -2,6 +2,20 @@
 
 describe Mongoid::Attributes do
 
+  describe "\#{attribute}" do
+
+    context "when setting the value in the getter" do
+
+      let(:account) do
+        Account.new
+      end
+
+      it "does not cause an infinite loop" do
+        account.overridden.should eq("not recommended")
+      end
+    end
+  end
+
   describe "#[]" do
 
     context "when the document is a new record" do