Array foreign key fields perform $addToSet ops via dirty tracking. Fixes

 #1530.

CHANGELOG.md

@@ -65,6 +65,9 @@ For instructions on upgrading to newer versions, visit
 * Calling `Document#as_document` on a frozen document on Rubinius returns the
   attributes instead of nil.
 
+* \#1530 Don't duplicate added values to arrays via dirty tracking if the
+  array is a foreign key field.
+
 * \#1523 Allow disabling of observers via `disable`. (Jonas Schneider)
 
 * \#1522 Fixed create indexes rake task for Rails 3.2. (Gray Manley)

lib/mongoid/atomic.rb

@@ -12,6 +12,7 @@ module Atomic
     UPDATES = [
       :atomic_array_pushes,
       :atomic_array_pulls,
+      :atomic_array_add_to_sets,
       :atomic_pulls,
       :atomic_unsets,
       :delayed_atomic_sets,
@@ -62,6 +63,18 @@ def atomic_array_pulls
       @atomic_array_pulls ||= {}
     end
 
+    # For array fields these are the unique adds that need to happen.
+    #
+    # @example Get the array unique adds.
+    #   person.atomic_array_add_to_sets
+    #
+    # @return [ Hash ] The array add_to_sets.
+    #
+    # @since 2.4.0
+    def atomic_array_add_to_sets
+      @atomic_array_add_to_sets ||= {}
+    end
+
     # Get all the atomic updates that need to happen for the current
     # +Document+. This includes all changes that need to happen in the
     # entire hierarchy that exists below where the save call was made.
@@ -259,6 +272,7 @@ def generate_atomic_updates(mods, doc)
       mods.set(doc.delayed_atomic_sets)
       mods.push(doc.atomic_pushes)
       mods.push(doc.atomic_array_pushes)
+      mods.add_to_set(doc.atomic_array_add_to_sets)
       mods.pull(doc.atomic_array_pulls)
     end
   end

lib/mongoid/atomic/modifiers.rb

@@ -6,6 +6,26 @@ module Atomic #:nodoc:
     # database.
     class Modifiers < Hash
 
+      # Add the atomic $addToSet modifiers to the hash.
+      #
+      # @example Add the $addToSet modifiers.
+      #   modifiers.add_to_set({ "preference_ids" => [ "one" ] })
+      #
+      # @param [ Hash ] modifications The add to set modifiers.
+      #
+      # @since 2.4.0
+      def add_to_set(modifications)
+        modifications.each_pair do |field, value|
+          if add_to_sets.has_key?(field)
+            value.each do |val|
+              add_to_sets[field]["$each"].push(val)
+            end
+          else
+            add_to_sets[field] = { "$each" => value }
+          end
+        end
+      end
+
       # Adds pull modifiers to the modifiers hash.
       #
       # @example Add pull operations.
@@ -90,6 +110,18 @@ def add_operation(mods, field, value)
         end
       end
 
+      # Get the $addToSet operations or intialize a new one.
+      #
+      # @example Get the $addToSet operations.
+      #   modifiers.add_to_sets
+      #
+      # @return [ Hash ] The $addToSet operations.
+      #
+      # @since 2.4.0
+      def add_to_sets
+        self["$addToSet"] ||= {}
+      end
+
       # Is the operation going to be a conflict for a $set?
       #
       # @example Is this a conflict for a set?
@@ -194,7 +226,7 @@ def set_fields
       # Get the $pullAll operations or intialize a new one.
       #
       # @example Get the $pullAll operations.
-      #   modifiers.pulles
+      #   modifiers.pulls
       #
       # @return [ Hash ] The $pullAll operations.
       #

lib/mongoid/dirty.rb

@@ -118,13 +118,7 @@ def setters
             key = embedded? ? "#{atomic_position}.#{name}" : name
             if field && field.resizable?
               pushes, pulls = new - (old || []), (old || []) - new
-              if pushes.any? && pulls.any?
-                modifications[key] = new
-              elsif pushes.any?
-                atomic_array_pushes[key] = pushes
-              else
-                atomic_array_pulls[key] = pulls
-              end
+              field.add_atomic_changes(self, key, modifications, pushes, pulls)
             else
               modifications[key] = new
             end

lib/mongoid/fields/internal/array.rb

@@ -7,6 +7,28 @@ module Internal #:nodoc:
       class Array
         include Serializable
 
+        # Adds the atomic changes for this type of resizable field.
+        #
+        # @example Add the atomic changes.
+        #   field.add_atomic_changes(doc, "key", {}, [], [])
+        #
+        # @param [ Document ] document The document to add to.
+        # @param [ String ] key The name of the field.
+        # @param [ Hash ] mods The current modifications.
+        # @param [ Array ] new The new elements to add.
+        # @param [ Array ] old The old elements getting removed.
+        #
+        # @since 2.4.0
+        def add_atomic_changes(document, key, mods, new, old)
+          if new.any? && old.any?
+            mods[key] = new
+          elsif new.any?
+            document.atomic_array_pushes[key] = new
+          elsif old.any?
+            document.atomic_array_pulls[key] = old
+          end
+        end
+
         # Array fields are resizable.
         #
         # @example Is this field resizable?

lib/mongoid/fields/internal/foreign_keys/array.rb

@@ -4,10 +4,32 @@ module Fields #:nodoc:
     module Internal #:nodoc:
       module ForeignKeys #:nodoc:
 
-        # Defines the behaviour for array fields.
+        # Defines the behaviour for array foreign key fields.
         class Array
           include Serializable
 
+          # Adds the atomic changes for this type of resizable field.
+          #
+          # @example Add the atomic changes.
+          #   field.add_atomic_changes(doc, "key", {}, [], [])
+          #
+          # @param [ Document ] document The document to add to.
+          # @param [ String ] key The name of the field.
+          # @param [ Hash ] mods The current modifications.
+          # @param [ Array ] new The new elements to add.
+          # @param [ Array ] old The old elements getting removed.
+          #
+          # @since 2.4.0
+          def add_atomic_changes(document, key, mods, new, old)
+            if new.any? && old.any?
+              mods[key] = new
+            elsif new.any?
+              document.atomic_array_add_to_sets[key] = new
+            elsif old.any?
+              document.atomic_array_pulls[key] = old
+            end
+          end
+
           # Is the field a BSON::ObjectId?
           #
           # @example Is the field a BSON::ObjectId?

spec/unit/mongoid/atomic/modifiers_spec.rb

@@ -6,6 +6,61 @@
     described_class.new
   end
 
+  describe "#add_to_set" do
+
+    context "when the unique adds are empty" do
+
+      before do
+        modifiers.add_to_set({})
+      end
+
+      it "does not contain any operations" do
+        modifiers.should eq({})
+      end
+    end
+
+    context "when the adds are not empty" do
+
+      let(:adds) do
+        { "preference_ids" => [ "one", "two" ] }
+      end
+
+      context "when adding a single field" do
+
+        before do
+          modifiers.add_to_set(adds)
+        end
+
+        it "adds the add to set with each modifiers" do
+          modifiers.should eq({
+            "$addToSet" => { "preference_ids" => { "$each" => [ "one", "two" ] }}
+          })
+        end
+      end
+
+      context "when adding to an existing field" do
+
+        let(:adds_two) do
+          { "preference_ids" => [ "three" ] }
+        end
+
+        before do
+          modifiers.add_to_set(adds)
+          modifiers.add_to_set(adds_two)
+        end
+
+        it "adds the add to set with each modifiers" do
+          modifiers.should eq({
+            "$addToSet" =>
+              { "preference_ids" =>
+                { "$each" => [ "one", "two", "three" ] }
+              }
+          })
+        end
+      end
+    end
+  end
+
   describe "#pull" do
 
     context "when the pulls are empty" do