Skip track without modifier

.gitignore

@@ -1,6 +1,7 @@
 Gemfile.lock
 
 .rvmrc
+.idea
 
 # rcov generated
 coverage

README.md

@@ -74,6 +74,7 @@ class Post
                   :modifier_field => :modifier, # adds "belongs_to :modifier" to track who made the change, default is :modifier
                   :modifier_field_inverse_of => :nil, # adds an ":inverse_of" option to the "belongs_to :modifier" relation, default is not set
                   :version_field => :version,   # adds "field :version, :type => Integer" to track current version, default is :version
+                  :track_without_modifier => true # save tracks when modifier is not set
                   :track_create   =>  false,    # track document creation, default is false
                   :track_update   =>  true,     # track document updates, default is true
                   :track_destroy  =>  false     # track document destruction, default is false
@@ -263,6 +264,27 @@ Or perhaps you are namespacing to a module:
 Mongoid::History.modifier_class_name = 'CMS::Author'
 ```
 
+**Skipping tracks without modifier set**
+
+If you don't want to save tracks when modifier for a model is not set, you can set `track_without_modifier` option to `false` either globally:
+
+```ruby
+  Mongoid::History.track_without_modifier = false
+```
+
+or per-model:
+
+```ruby
+class Post
+  include Mongoid::Document
+  include Mongoid::History::Trackable
+  field           :title
+  field           :body
+
+  track_history   :on => [:title, :body], :track_without_modifier => false
+end
+```
+
 **Using an alternate changes method**
 
 Sometimes you may wish to provide an alternate method for determining which changes should be tracked.  For example, if you are using embedded documents

lib/mongoid/history.rb

@@ -13,6 +13,7 @@ module History
     mattr_accessor :trackable_class_options
     mattr_accessor :modifier_class_name
     mattr_accessor :current_user_method
+    mattr_accessor :track_without_modifier
 
     def self.tracker_class
       @tracker_class ||= tracker_class_name.to_s.classify.constantize
@@ -34,3 +35,5 @@ def self.enabled?
 Mongoid::History.modifier_class_name = 'User'
 Mongoid::History.trackable_class_options = {}
 Mongoid::History.current_user_method ||= :current_user
+Mongoid::History.track_without_modifier = true
+

lib/mongoid/history/trackable.rb

@@ -13,6 +13,7 @@ def track_history(options = {})
             version_field: :version,
             changes_method: :changes,
             scope: scope_name,
+            track_without_modifier: Mongoid::History.track_without_modifier,
             track_create: false,
             track_update: true,
             track_destroy: false
@@ -276,7 +277,9 @@ def transform_changes(changes)
         protected
 
         def track_history_for_action?(action)
-          track_history? && !(action.to_sym == :update && modified_attributes_for_update.blank?)
+          track_history? &&
+            !(action.to_sym == :update && modified_attributes_for_update.blank?) &&
+            (history_trackable_options[:track_without_modifier] || !!send(history_trackable_options[:modifier_field]))
         end
 
         def track_history_for_action(action)

lib/mongoid/history/tracker.rb

@@ -14,7 +14,7 @@ module Tracker
         field :version,                 type: Integer
         field :action,                  type: String
         field :scope,                   type: String
-        belongs_to :modifier,                class_name: Mongoid::History.modifier_class_name
+        belongs_to :modifier,           class_name: Mongoid::History.modifier_class_name
 
         index(scope: 1)
         index(association_chain: 1)