Merge branch 'master' into nested_has_many_through

Conflicts:
	activerecord/CHANGELOG
	activerecord/lib/active_record/association_preload.rb
	activerecord/lib/active_record/associations.rb
	activerecord/lib/active_record/associations/class_methods/join_dependency.rb
	activerecord/lib/active_record/associations/class_methods/join_dependency/join_association.rb
	activerecord/lib/active_record/associations/has_many_association.rb
	activerecord/lib/active_record/associations/has_many_through_association.rb
	activerecord/lib/active_record/associations/has_one_association.rb
	activerecord/lib/active_record/associations/has_one_through_association.rb
	activerecord/lib/active_record/associations/through_association_scope.rb
	activerecord/lib/active_record/reflection.rb
	activerecord/test/cases/associations/has_many_through_associations_test.rb
	activerecord/test/cases/associations/has_one_through_associations_test.rb
	activerecord/test/cases/reflection_test.rb
	activerecord/test/cases/relations_test.rb
	activerecord/test/fixtures/memberships.yml
	activerecord/test/models/categorization.rb
	activerecord/test/models/category.rb
	activerecord/test/models/member.rb
	activerecord/test/models/reference.rb
	activerecord/test/models/tagging.rb

1 files changed, 262 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/associations/association.rb b/activerecord/lib/active_record/associations/association.rb
new file mode 100644
index 0000000000..86904ea2bc
--- /dev/null
+++ b/activerecord/lib/active_record/associations/association.rb
@@ -0,0 +1,262 @@
+require 'active_support/core_ext/array/wrap'
+
+module ActiveRecord
+  module Associations
+    # = Active Record Associations
+    #
+    # This is the root class of all associations ('+ Foo' signifies an included module Foo):
+    #
+    #   Association
+    #     SingularAssociaton
+    #       HasOneAssociation
+    #         HasOneThroughAssociation + ThroughAssociation
+    #       BelongsToAssociation
+    #         BelongsToPolymorphicAssociation
+    #     CollectionAssociation
+    #       HasAndBelongsToManyAssociation
+    #       HasManyAssociation
+    #         HasManyThroughAssociation + ThroughAssociation
+    class Association #:nodoc:
+      attr_reader :owner, :target, :reflection
+
+      delegate :options, :to => :reflection
+
+      def initialize(owner, reflection)
+        reflection.check_validity!
+
+        @target = nil
+        @owner, @reflection = owner, reflection
+        @updated = false
+
+        reset
+        construct_scope
+      end
+
+      # Returns the name of the table of the related class:
+      #
+      #   post.comments.aliased_table_name # => "comments"
+      #
+      def aliased_table_name
+        reflection.klass.table_name
+      end
+
+      # Resets the \loaded flag to +false+ and sets the \target to +nil+.
+      def reset
+        @loaded = false
+        IdentityMap.remove(target) if IdentityMap.enabled? && target
+        @target = nil
+      end
+
+      # Reloads the \target and returns +self+ on success.
+      def reload
+        reset
+        construct_scope
+        load_target
+        self unless target.nil?
+      end
+
+      # Has the \target been already \loaded?
+      def loaded?
+        @loaded
+      end
+
+      # Asserts the \target has been loaded setting the \loaded flag to +true+.
+      def loaded!
+        @loaded      = true
+        @stale_state = stale_state
+      end
+
+      # The target is stale if the target no longer points to the record(s) that the
+      # relevant foreign_key(s) refers to. If stale, the association accessor method
+      # on the owner will reload the target. It's up to subclasses to implement the
+      # state_state method if relevant.
+      #
+      # Note that if the target has not been loaded, it is not considered stale.
+      def stale_target?
+        loaded? && @stale_state != stale_state
+      end
+
+      # Sets the target of this association to <tt>\target</tt>, and the \loaded flag to +true+.
+      def target=(target)
+        @target = target
+        loaded!
+      end
+
+      def scoped
+        target_scope.merge(@association_scope)
+      end
+
+      # Construct the scope for this association.
+      #
+      # Note that the association_scope is merged into the targed_scope only when the
+      # scoped method is called. This is because at that point the call may be surrounded
+      # by scope.scoping { ... } or with_scope { ... } etc, which affects the scope which
+      # actually gets built.
+      def construct_scope
+        @association_scope = association_scope if klass
+      end
+
+      def association_scope
+        scope = klass.unscoped
+        scope = scope.create_with(creation_attributes)
+        scope = scope.apply_finder_options(options.slice(:readonly, :include))
+        scope = scope.where(interpolate(options[:conditions]))
+        if select = select_value
+          scope = scope.select(select)
+        end
+        scope = scope.extending(*Array.wrap(options[:extend]))
+        scope.where(construct_owner_conditions)
+      end
+
+      def aliased_table
+        klass.arel_table
+      end
+
+      # Set the inverse association, if possible
+      def set_inverse_instance(record)
+        if record && invertible_for?(record)
+          inverse = record.association(inverse_reflection_for(record).name)
+          inverse.target = owner
+        end
+      end
+
+      # This class of the target. belongs_to polymorphic overrides this to look at the
+      # polymorphic_type field on the owner.
+      def klass
+        reflection.klass
+      end
+
+      # Can be overridden (i.e. in ThroughAssociation) to merge in other scopes (i.e. the
+      # through association's scope)
+      def target_scope
+        klass.scoped
+      end
+
+      # Loads the \target if needed and returns it.
+      #
+      # This method is abstract in the sense that it relies on +find_target+,
+      # which is expected to be provided by descendants.
+      #
+      # If the \target is already \loaded it is just returned. Thus, you can call
+      # +load_target+ unconditionally to get the \target.
+      #
+      # ActiveRecord::RecordNotFound is rescued within the method, and it is
+      # not reraised. The proxy is \reset and +nil+ is the return value.
+      def load_target
+        if find_target?
+          begin
+            if IdentityMap.enabled? && association_class && association_class.respond_to?(:base_class)
+              @target = IdentityMap.get(association_class, owner[reflection.foreign_key])
+            end
+          rescue NameError
+            nil
+          ensure
+            @target ||= find_target
+          end
+        end
+        loaded!
+        target
+      rescue ActiveRecord::RecordNotFound
+        reset
+      end
+
+      private
+
+        def find_target?
+          !loaded? && (!owner.new_record? || foreign_key_present?) && klass
+        end
+
+        def interpolate(sql, record = nil)
+          if sql.respond_to?(:to_proc)
+            owner.send(:instance_exec, record, &sql)
+          else
+            sql
+          end
+        end
+
+        def select_value
+          options[:select]
+        end
+
+        # Implemented by (some) subclasses
+        def creation_attributes
+          { }
+        end
+
+        # Returns a hash linking the owner to the association represented by the reflection
+        def construct_owner_attributes(reflection = reflection)
+          attributes = {}
+          if reflection.macro == :belongs_to
+            attributes[reflection.association_primary_key] = owner[reflection.foreign_key]
+          else
+            attributes[reflection.foreign_key] = owner[reflection.active_record_primary_key]
+
+            if options[:as]
+              attributes["#{options[:as]}_type"] = owner.class.base_class.name
+            end
+          end
+          attributes
+        end
+
+        # Builds an array of arel nodes from the owner attributes hash
+        def construct_owner_conditions(table = aliased_table, reflection = reflection)
+          conditions = construct_owner_attributes(reflection).map do |attr, value|
+            table[attr].eq(value)
+          end
+          table.create_and(conditions)
+        end
+
+        # Sets the owner attributes on the given record
+        def set_owner_attributes(record)
+          if owner.persisted?
+            construct_owner_attributes.each { |key, value| record[key] = value }
+          end
+        end
+
+        # Should be true if there is a foreign key present on the owner which
+        # references the target. This is used to determine whether we can load
+        # the target if the owner is currently a new record (and therefore
+        # without a key).
+        #
+        # Currently implemented by belongs_to (vanilla and polymorphic) and
+        # has_one/has_many :through associations which go through a belongs_to
+        def foreign_key_present?
+          false
+        end
+
+        # Raises ActiveRecord::AssociationTypeMismatch unless +record+ is of
+        # the kind of the class of the associated objects. Meant to be used as
+        # a sanity check when you are about to assign an associated record.
+        def raise_on_type_mismatch(record)
+          unless record.is_a?(reflection.klass) || record.is_a?(reflection.class_name.constantize)
+            message = "#{reflection.class_name}(##{reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})"
+            raise ActiveRecord::AssociationTypeMismatch, message
+          end
+        end
+
+        # Can be redefined by subclasses, notably polymorphic belongs_to
+        # The record parameter is necessary to support polymorphic inverses as we must check for
+        # the association in the specific class of the record.
+        def inverse_reflection_for(record)
+          reflection.inverse_of
+        end
+
+        # Is this association invertible? Can be redefined by subclasses.
+        def invertible_for?(record)
+          inverse_reflection_for(record)
+        end
+
+        # This should be implemented to return the values of the relevant key(s) on the owner,
+        # so that when state_state is different from the value stored on the last find_target,
+        # the target is stale.
+        #
+        # This is only relevant to certain associations, which is why it returns nil by default.
+        def stale_state
+        end
+
+        def association_class
+          @reflection.klass
+        end
+    end
+  end
+end