belongs_to supports :dependent => :destroy and :delete. Closes #10592.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8675 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

 *SVN*
 
+* belongs_to supports :dependent => :destroy and :delete.  #10592 [Jonathan Viney]
+
 * Introduce preload query strategy for eager :includes.  #9640 [Frederick Cheung, Aleksey Kondratenko]
 
 * Support aggregations in finder conditions.  #10572 [Ryan Kinderman]

activerecord/lib/active_record/associations.rb

@@ -792,6 +792,10 @@ def has_one(association_id, options = {})
       # * <tt>:foreign_key</tt> - specify the foreign key used for the association. By default this is guessed to be the name
       #   of the association with an +_id+ suffix. So a class that defines a +belongs_to :person+ association will use +person_id+ as the default +foreign_key+.
       #   Similarly, +belongs_to :favorite_person, :class_name => "Person"+ will use a foreign key of +favorite_person_id+.
+      # * <tt>:dependent</tt>   - if set to <tt>:destroy</tt>, the associated object is destroyed when this object is. If set to
+      #   <tt>:delete</tt>, the associated object is deleted *without* calling its destroy method. This option should not be specified when
+      #   <tt>belongs_to</tt> is used in conjunction with a <tt>has_many</tt> relationship on another class because of the potential to leave
+      #   orphaned records behind.
       # * <tt>:counter_cache</tt> - caches the number of belonging objects on the associate class through the use of +increment_counter+
       #   and +decrement_counter+. The counter cache is incremented when an object of this class is created and decremented when it's
       #   destroyed. This requires that a column named <tt>#{table_name}_count</tt> (such as +comments_count+ for a belonging +Comment+ class)
@@ -876,6 +880,8 @@ def belongs_to(association_id, options = {})
             "#{reflection.class_name}.send(:attr_readonly,\"#{cache_column}\".intern) if defined?(#{reflection.class_name}) && #{reflection.class_name}.respond_to?(:attr_readonly)"
           )
         end
+
+        configure_dependency_for_belongs_to(reflection)
       end
 
       # Associates two classes via an intermediate join table.  Unless the join table is explicitly specified as
@@ -1202,6 +1208,19 @@ def configure_dependency_for_has_one(reflection)
           end
         end
 
+        def configure_dependency_for_belongs_to(reflection)
+          if reflection.options.include?(:dependent)
+            case reflection.options[:dependent]
+              when :destroy
+                module_eval "before_destroy '#{reflection.name}.destroy unless #{reflection.name}.nil?'"
+              when :delete
+                module_eval "before_destroy '#{reflection.class_name}.delete(#{reflection.name}.id) unless #{reflection.name}.nil?'"
+              else
+                raise ArgumentError, "The :dependent option expects either :destroy or :delete (#{reflection.options[:dependent].inspect})"
+            end
+          end
+        end
+
         def create_has_many_reflection(association_id, options, &extension)
           options.assert_valid_keys(
             :class_name, :table_name, :foreign_key,

activerecord/test/cases/associations_test.rb

@@ -470,7 +470,7 @@ def test_save_still_works_after_accessing_nil_has_one
 
 class HasManyAssociationsTest < ActiveSupport::TestCase
   fixtures :accounts, :companies, :developers, :projects,
-           :developers_projects, :topics, :authors, :comments
+           :developers_projects, :topics, :authors, :comments, :author_addresses
 
   def setup
     Client.destroyed_client_ids.clear
@@ -995,6 +995,23 @@ def test_dependent_association_respects_optional_sanitized_conditions_on_delete
     assert_equal 1, Client.find_all_by_client_of(firm.id).size
   end
 
+  def test_dependent_delete_and_destroy_with_belongs_to
+    author_address = author_addresses(:david_address)
+    assert_equal [], AuthorAddress.destroyed_author_address_ids[authors(:david).id]
+
+    assert_difference "AuthorAddress.count", -2 do
+      authors(:david).destroy
+    end
+
+    assert_equal [author_address.id], AuthorAddress.destroyed_author_address_ids[authors(:david).id]
+  end
+
+  def test_invalid_belongs_to_dependent_option_raises_exception
+    assert_raises ArgumentError do
+      Author.belongs_to :special_author_address, :dependent => :nullify
+    end
+  end
+
   def test_clearing_without_initial_access
     firm = companies(:first_firm)
 

activerecord/test/cases/json_serialization_test.rb

@@ -151,7 +151,7 @@ def test_should_allow_only_option_for_list_of_authors
   def test_should_allow_except_option_for_list_of_authors
     authors = [@david, @mary]
 
-    assert_equal %([{"id": 1}, {"id": 2}]), authors.to_json(:except => [:name, :author_address_id])
+    assert_equal %([{"id": 1}, {"id": 2}]), authors.to_json(:except => [:name, :author_address_id, :author_address_extra_id])
   end
 
   def test_should_allow_includes_for_list_of_authors

activerecord/test/fixtures/authors.yml

 david:
   id: 1
   name: David
+  author_address_id: 1
+  author_address_extra_id: 2
 
 mary:
   id: 2

activerecord/test/models/author.rb

@@ -65,7 +65,8 @@ def testing_proxy_target
   has_many :tags,     :through => :posts # through has_many :through
   has_many :post_categories, :through => :posts, :source => :categories
 
-  belongs_to :author_address
+  belongs_to :author_address, :dependent => :destroy
+  belongs_to :author_address_extra, :dependent => :delete, :class_name => "AuthorAddress"
 
   attr_accessor :post_log
 
@@ -101,6 +102,17 @@ def raise_exception(object)
 
 class AuthorAddress < ActiveRecord::Base
   has_one :author
+
+  def self.destroyed_author_address_ids
+    @destroyed_author_address_ids ||= Hash.new { |h,k| h[k] = [] }
+  end
+
+  before_destroy do |author_address|
+    if author_address.author
+      AuthorAddress.destroyed_author_address_ids[author_address.author.id] << author_address.id
+    end
+    true
+  end
 end
 
 class AuthorFavorite < ActiveRecord::Base

activerecord/test/schema/schema.rb

@@ -239,9 +239,9 @@ def create_table(*args, &block)
 
   add_column :posts, :taggings_count, :integer, :default => 0
   add_column :authors, :author_address_id, :integer
+  add_column :authors, :author_address_extra_id, :integer
 
   create_table :author_addresses, :force => true do |t|
-    t.column :author_address_id, :integer
   end
 
   create_table :author_favorites, :force => true do |t|