Add :dependent = to has_one and has_many [#3075 state:resolved]

activerecord/lib/active_record/associations.rb

@@ -86,6 +86,15 @@ module ActiveRecord
     end
   end
 
+  # This error is raised when trying to destroy a parent instance in a N:1, 1:1 assosications
+  # (has_many, has_one) when there is at least 1 child assosociated instance.
+  # ex: if @project.tasks.size > 0, DeleteRestrictionError will be raised when trying to destroy @project
+  class DeleteRestrictionError < ActiveRecordError #:nodoc:
+    def initialize(reflection)
+      super("Cannot delete record because of dependent #{reflection.name}")
+    end
+  end
+
   # See ActiveRecord::Associations::ClassMethods for documentation.
   module Associations # :nodoc:
     extend ActiveSupport::Concern
@@ -831,6 +840,8 @@ module ActiveRecord
       #   objects are deleted *without* calling their +destroy+ method.  If set to <tt>:nullify</tt> all associated
       #   objects' foreign keys are set to +NULL+ *without* calling their +save+ callbacks. *Warning:* This option is ignored when also using
       #   the <tt>:through</tt> option.
+      #   the <tt>:through</tt> option. If set to <tt>:restrict</tt>
+      #   this object cannot be deleted if it has any associated object.
       # [:finder_sql]
       #   Specify a complete SQL statement to fetch the association. This is a good way to go for complex
       #   associations that depend on multiple tables. Note: When this option is used, +find_in_collection+ is _not_ added.
@@ -1469,9 +1480,15 @@ module ActiveRecord
 
         # Creates before_destroy callback methods that nullify, delete or destroy
         # has_many associated objects, according to the defined :dependent rule.
+        # If the association is marked as :dependent => :restrict, create a callback
+        # that prevents deleting entirely.
         #
         # See HasManyAssociation#delete_records.  Dependent associations
         # delete children, otherwise foreign key is set to NULL.
+        # See HasManyAssociation#delete_records. Dependent associations
+        # delete children if the option is set to :destroy or :delete_all, set the
+        # foreign key to NULL if the option is set to :nullify, and do not touch the
+        # child records if the option is set to :restrict.
         #
         # The +extra_conditions+ parameter, which is not used within the main
         # Active Record codebase, is meant to allow plugins to define extra
@@ -1531,14 +1548,24 @@ module ActiveRecord
                       %@#{dependent_conditions}@)
                   end
                 CALLBACK
+                when :restrict
+                  method_name = "has_many_dependent_restrict_for_#{reflection.name}".to_sym
+                  define_method(method_name) do
+                    unless send(reflection.name).empty?
+                      raise DeleteRestrictionError.new(reflection)
+                    end
+                  end
+                  before_destroy method_name
               else
-                raise ArgumentError, "The :dependent option expects either :destroy, :delete_all, or :nullify (#{reflection.options[:dependent].inspect})"
+                raise ArgumentError, "The :dependent option expects either :destroy, :delete_all, :nullify or :restrict (#{reflection.options[:dependent].inspect})"
             end
           end
         end
 
         # Creates before_destroy callback methods that nullify, delete or destroy
         # has_one associated objects, according to the defined :dependent rule.
+        # If the association is marked as :dependent => :restrict, create a callback
+        # that prevents deleting entirely.
         def configure_dependency_for_has_one(reflection)
           if reflection.options.include?(:dependent)
             name = reflection.options[:dependent]
@@ -1559,8 +1586,16 @@ module ActiveRecord
                     association.update_attribute(#{reflection.primary_key_name.inspect}, nil) if association
                   end
                 eoruby
+              when :restrict
+                method_name = "has_one_dependent_restrict_for_#{reflection.name}".to_sym
+                define_method(method_name) do
+                  unless send(reflection.name).nil?
+                    raise DeleteRestrictionError.new(reflection)
+                  end
+                end
+                before_destroy method_name
               else
-                raise ArgumentError, "The :dependent option expects either :destroy, :delete or :nullify (#{reflection.options[:dependent].inspect})"
+                raise ArgumentError, "The :dependent option expects either :destroy, :delete, :nullify or :restrict (#{reflection.options[:dependent].inspect})"
             end
 
             before_destroy method_name

activerecord/test/cases/associations/belongs_to_associations_test.rb

@@ -439,9 +439,15 @@ class BelongsToAssociationsTest < ActiveRecord::TestCase
     assert_equal [author_address.id], AuthorAddress.destroyed_author_address_ids
   end
 
-  def test_invalid_belongs_to_dependent_option_raises_exception
+  def test_invalid_belongs_to_dependent_option_nullify_raises_exception
     assert_raise ArgumentError do
       Author.belongs_to :special_author_address, :dependent => :nullify
     end
   end
+  
+  def test_invalid_belongs_to_dependent_option_restrict_raises_exception
+    assert_raise ArgumentError do
+      Author.belongs_to :special_author_address, :dependent => :restrict
+    end
+  end
 end

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -836,6 +836,14 @@ class HasManyAssociationsTest < ActiveRecord::TestCase
     assert_equal num_accounts, Account.count
   end
 
+  def test_restrict
+    firm = RestrictedFirm.new(:name => 'restrict')
+    firm.save!
+    child_firm = firm.companies.create(:name => 'child')
+    assert !firm.companies.empty?
+    assert_raise(ActiveRecord::DeleteRestrictionError) { firm.destroy }
+  end
+
   def test_included_in_collection
     assert companies(:first_firm).clients.include?(Client.find(2))
   end

activerecord/test/cases/associations/has_one_associations_test.rb

@@ -177,7 +177,15 @@ class HasOneAssociationsTest < ActiveRecord::TestCase
     assert_nothing_raised { firm.destroy }
   end
 
-  def test_succesful_build_association
+  def test_dependence_with_restrict
+    firm = RestrictedFirm.new(:name => 'restrict')
+    firm.save!
+    account = firm.create_account(:credit_limit => 10)
+    assert !firm.account.nil?
+    assert_raise(ActiveRecord::DeleteRestrictionError) { firm.destroy }
+  end
+
+  def test_successful_build_association
     firm = Firm.new("name" => "GlobalMegaCorp")
     firm.save
 

activerecord/test/models/company.rb

@@ -95,6 +95,11 @@ class DependentFirm < Company
   has_many :companies, :foreign_key => 'client_of', :dependent => :nullify
 end
 
+class RestrictedFirm < Company
+  has_one :account, :foreign_key => "firm_id", :dependent => :restrict, :order => "id"
+  has_many :companies, :foreign_key => 'client_of', :order => "id", :dependent => :restrict
+end
+
 class Client < Company
   belongs_to :firm, :foreign_key => "client_of"
   belongs_to :firm_with_basic_id, :class_name => "Firm", :foreign_key => "firm_id"