Merge remote branch 'jonleighton/association_fixes'

* jonleighton/association_fixes:
  Add a transaction wrapper in add_to_target. This means that #build will now also use a transaction. IMO this is reasonable given that the before_add and after_add callbacks might do anything, and this great consistency allows us to abstract out the duplicate code from #build and #create.
  Inline ensure_owner_is_persisted! as it is only called from one place
  @target should always be an array
  Rename add_record_to_target_with_callbacks to add_to_target
  Don't pass the block through build_record
  Move create and create! next to build
  Get rid of create_record as it is not only used in one place
  Get rid of AssociationCollection#save_record
  Fix test/cases/connection_pool_test.rb for sqlite3 in-memory db
  Add interpolation of association conditions back in, in the form of proc { ... } rather than instance_eval-ing strings

activerecord/CHANGELOG

@@ -50,8 +50,27 @@
   (for example, add_name_to_users) use the reversible migration's `change`
   method instead of the ordinary `up` and `down` methods. [Prem Sichanugrist]
 
-* Removed support for interpolated SQL conditions.  Please use scoping
-along with attribute conditionals as a replacement.
+* Removed support for interpolating string SQL conditions on associations. Instead, you should
+  use a proc, like so:
+
+  Before:
+
+    has_many :things, :conditions => 'foo = #{bar}'
+
+  After:
+
+    has_many :things, :conditions => proc { "foo = #{bar}" }
+
+  Inside the proc, 'self' is the object which is the owner of the association, unless you are
+  eager loading the association, in which case 'self' is the class which the association is within.
+
+  You can have any "normal" conditions inside the proc, so the following will work too:
+
+    has_many :things, :conditions => proc { ["foo = ?", bar] }
+
+  Previously :insert_sql and :delete_sql on has_and_belongs_to_many association allowed you to call
+  'record' to get the record being inserted or deleted. This is now passed as an argument to
+  the proc.
 
 * Added ActiveRecord::Base#has_secure_password (via ActiveModel::SecurePassword) to encapsulate dead-simple password usage with BCrypt encryption and salting [DHH]. Example:
 

activerecord/lib/active_record/association_preload.rb

@@ -399,10 +399,18 @@ def find_associated_records(ids, reflection, preload_options)
         end
       end
 
+      def process_conditions(conditions, klass = self)
+        if conditions.respond_to?(:to_proc)
+          conditions = instance_eval(&conditions)
+        end
+
+        klass.send(:sanitize_sql, conditions)
+      end
+
       def append_conditions(reflection, preload_options)
         [
-          ("(#{reflection.sanitized_conditions})" if reflection.sanitized_conditions),
-          ("(#{sanitize_sql preload_options[:conditions]})" if preload_options[:conditions]),
+          ('(' + process_conditions(reflection.options[:conditions], reflection.klass) + ')' if reflection.options[:conditions]),
+          ('(' + process_conditions(preload_options[:conditions]) + ')' if preload_options[:conditions]),
         ].compact.map { |x| Arel.sql x }
       end
 

activerecord/lib/active_record/associations/association_collection.rb

@@ -56,14 +56,21 @@ def reset
       end
 
       def build(attributes = {}, &block)
-        if attributes.is_a?(Array)
-          attributes.collect { |attr| build(attr, &block) }
-        else
-          build_record(attributes) do |record|
-            block.call(record) if block_given?
-            set_owner_attributes(record)
-          end
+        build_or_create(attributes, :build, &block)
+      end
+
+      def create(attributes = {}, &block)
+        unless @owner.persisted?
+          raise ActiveRecord::RecordNotSaved, "You cannot call create unless the parent is saved"
         end
+
+        build_or_create(attributes, :create, &block)
+      end
+
+      def create!(attrs = {}, &block)
+        record = create(attrs, &block)
+        Array.wrap(record).each(&:save!)
+        record
       end
 
       # Add +records+ to this association.  Returns +self+ so method calls may be chained.
@@ -75,7 +82,7 @@ def <<(*records)
         transaction do
           records.flatten.each do |record|
             raise_on_type_mismatch(record)
-            add_record_to_target_with_callbacks(record) do |r|
+            add_to_target(record) do |r|
               result &&= insert_record(record) unless @owner.new_record?
             end
           end
@@ -191,24 +198,6 @@ def destroy(*records)
         delete_or_destroy(records, :destroy)
       end
 
-      def create(attrs = {})
-        if attrs.is_a?(Array)
-          attrs.collect { |attr| create(attr) }
-        else
-          create_record(attrs) do |record|
-            yield(record) if block_given?
-            insert_record(record, false)
-          end
-        end
-      end
-
-      def create!(attrs = {})
-        create_record(attrs) do |record|
-          yield(record) if block_given?
-          insert_record(record, true)
-        end
-      end
-
       # Returns the size of the collection by executing a SELECT COUNT(*)
       # query if the collection hasn't been loaded, and calling
       # <tt>collection.size</tt> if it has.
@@ -348,17 +337,21 @@ def load_target
           target
         end
 
-        def add_record_to_target_with_callbacks(record)
-          callback(:before_add, record)
-          yield(record) if block_given?
-          @target ||= [] unless loaded?
-          if @reflection.options[:uniq] && index = @target.index(record)
-            @target[index] = record
-          else
-            @target << record
+        def add_to_target(record)
+          transaction do
+            callback(:before_add, record)
+            yield(record) if block_given?
+
+            if @reflection.options[:uniq] && index = @target.index(record)
+              @target[index] = record
+            else
+              @target << record
+            end
+
+            callback(:after_add, record)
+            set_inverse_instance(record)
           end
-          callback(:after_add, record)
-          set_inverse_instance(record)
+
           record
         end
 
@@ -374,17 +367,15 @@ def uniq_select_value
 
         def custom_counter_sql
           if @reflection.options[:counter_sql]
-            counter_sql = @reflection.options[:counter_sql]
+            interpolate(@reflection.options[:counter_sql])
           else
             # replace the SELECT clause with COUNT(*), preserving any hints within /* ... */
-            counter_sql = @reflection.options[:finder_sql].sub(/SELECT\b(\/\*.*?\*\/ )?(.*)\bFROM\b/im) { "SELECT #{$1}COUNT(*) FROM" }
+            interpolate(@reflection.options[:finder_sql]).sub(/SELECT\b(\/\*.*?\*\/ )?(.*)\bFROM\b/im) { "SELECT #{$1}COUNT(*) FROM" }
           end
-
-          interpolate_sql(counter_sql)
         end
 
         def custom_finder_sql
-          interpolate_sql(@reflection.options[:finder_sql])
+          interpolate(@reflection.options[:finder_sql])
         end
 
         def find_target
@@ -421,26 +412,26 @@ def merge_target_lists(loaded, existing)
           end + existing
         end
 
-        # Do the relevant stuff to insert the given record into the association collection. The
-        # force param specifies whether or not an exception should be raised on failure. The
-        # validate param specifies whether validation should be performed (if force is false).
-        def insert_record(record, force = true, validate = true)
-          raise NotImplementedError
-        end
+        def build_or_create(attributes, method)
+          records = Array.wrap(attributes).map do |attrs|
+            record = build_record(attrs)
+
+            add_to_target(record) do
+              yield(record) if block_given?
+              insert_record(record) if method == :create
+            end
+          end
 
-        def save_record(record, force, validate)
-          force ? record.save! : record.save(:validate => validate)
+          attributes.is_a?(Array) ? records : records.first
         end
 
-        def create_record(attributes, &block)
-          ensure_owner_is_persisted!
-          transaction { build_record(attributes, &block) }
+        # Do the relevant stuff to insert the given record into the association collection.
+        def insert_record(record, validate = true)
+          raise NotImplementedError
         end
 
-        def build_record(attributes, &block)
-          attributes = scoped.scope_for_create.merge(attributes)
-          record = @reflection.build_association(attributes)
-          add_record_to_target_with_callbacks(record, &block)
+        def build_record(attributes)
+          @reflection.build_association(scoped.scope_for_create.merge(attributes))
         end
 
         def delete_or_destroy(records, method)
@@ -482,12 +473,6 @@ def callbacks_for(callback_name)
           @owner.class.send(full_callback_name.to_sym) || []
         end
 
-        def ensure_owner_is_persisted!
-          unless @owner.persisted?
-            raise ActiveRecord::RecordNotSaved, "You cannot call create unless the parent is saved"
-          end
-        end
-
         # Should we deal with assoc.first or assoc.last by issuing an independent query to
         # the database, or by getting the target, and then taking the first/last item from that?
         #

activerecord/lib/active_record/associations/association_proxy.rb

@@ -184,7 +184,8 @@ def construct_scope
         def association_scope
           scope = target_klass.unscoped
           scope = scope.create_with(creation_attributes)
-          scope = scope.apply_finder_options(@reflection.options.slice(:conditions, :readonly, :include))
+          scope = scope.apply_finder_options(@reflection.options.slice(:readonly, :include))
+          scope = scope.where(interpolate(@reflection.options[:conditions]))
           if select = select_value
             scope = scope.select(select)
           end
@@ -240,8 +241,12 @@ def find_target?
           !loaded? && (!@owner.new_record? || foreign_key_present?) && target_klass
         end
 
-        def interpolate_sql(sql, record = nil)
-          @owner.send(:interpolate_sql, sql, record)
+        def interpolate(sql, record = nil)
+          if sql.respond_to?(:to_proc)
+            @owner.send(:instance_exec, record, &sql)
+          else
+            sql
+          end
         end
 
         def select_value

activerecord/lib/active_record/associations/class_methods/join_dependency/join_association.rb

@@ -108,6 +108,10 @@ def allocate_aliases
           end
 
           def process_conditions(conditions, table_name)
+            if conditions.respond_to?(:to_proc)
+              conditions = instance_eval(&conditions)
+            end
+
             Arel.sql(sanitize_sql(conditions, table_name))
           end
 

activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb

@@ -11,13 +11,11 @@ def initialize(owner, reflection)
 
       protected
 
-        def insert_record(record, force = true, validate = true)
-          if record.new_record?
-            return false unless save_record(record, force, validate)
-          end
+        def insert_record(record, validate = true)
+          return if record.new_record? && !record.save(:validate => validate)
 
           if @reflection.options[:insert_sql]
-            @owner.connection.insert(interpolate_sql(@reflection.options[:insert_sql], record))
+            @owner.connection.insert(interpolate(@reflection.options[:insert_sql], record))
           else
             stmt = join_table.compile_insert(
               join_table[@reflection.foreign_key]             => @owner.id,
@@ -27,7 +25,7 @@ def insert_record(record, force = true, validate = true)
             @owner.connection.insert stmt.to_sql
           end
 
-          true
+          record
         end
 
         def association_scope
@@ -42,7 +40,7 @@ def count_records
 
         def delete_records(records, method)
           if sql = @reflection.options[:delete_sql]
-            records.each { |record| @owner.connection.delete(interpolate_sql(sql, record)) }
+            records.each { |record| @owner.connection.delete(interpolate(sql, record)) }
           else
             relation = join_table
             stmt = relation.where(relation[@reflection.foreign_key].eq(@owner.id).

activerecord/lib/active_record/associations/has_many_association.rb

@@ -8,9 +8,9 @@ module Associations
     class HasManyAssociation < AssociationCollection #:nodoc:
       protected
 
-        def insert_record(record, force = false, validate = true)
+        def insert_record(record, validate = true)
           set_owner_attributes(record)
-          save_record(record, force, validate)
+          record.save(:validate => validate)
         end
 
       private

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -22,12 +22,21 @@ def size
         end
       end
 
+      def <<(*records)
+        unless @owner.new_record?
+          records.flatten.each do |record|
+            raise_on_type_mismatch(record)
+            record.save! if record.new_record?
+          end
+        end
+
+        super
+      end
+
       protected
 
-        def insert_record(record, force = true, validate = true)
-          if record.new_record?
-            return unless save_record(record, force, validate)
-          end
+        def insert_record(record, validate = true)
+          return if record.new_record? && !record.save(:validate => validate)
 
           through_association = @owner.send(@reflection.through_reflection.name)
           through_association.create!(construct_join_attributes(record))

activerecord/lib/active_record/associations/through_association.rb

@@ -119,14 +119,14 @@ def add_conditions(scope)
             scope = scope.where(@reflection.through_reflection.klass.send(:type_condition))
           end
 
-          scope = scope.where(@reflection.source_reflection.options[:conditions])
+          scope = scope.where(interpolate(@reflection.source_reflection.options[:conditions]))
           scope.where(through_conditions)
         end
 
         # If there is a hash of conditions then we make sure the keys are scoped to the
         # through table name if left ambiguous.
         def through_conditions
-          conditions = @reflection.through_reflection.options[:conditions]
+          conditions = interpolate(@reflection.through_reflection.options[:conditions])
 
           if conditions.is_a?(Hash)
             Hash[conditions.map { |key, value|

activerecord/lib/active_record/autosave_association.rb

@@ -312,7 +312,7 @@ def save_collection_association(reflection)
               association.destroy(record)
             elsif autosave != false && (@new_record_before_save || record.new_record?)
               if autosave
-                saved = association.send(:insert_record, record, false, false)
+                saved = association.send(:insert_record, record, false)
               else
                 association.send(:insert_record, record)
               end

activerecord/lib/active_record/base.rb

@@ -1790,12 +1790,6 @@ def quote_value(value, column = nil)
         self.class.connection.quote(value, column)
       end
 
-      # Interpolate custom SQL string in instance context.
-      # Optional record argument is meant for custom insert_sql.
-      def interpolate_sql(sql, record = nil)
-        instance_eval("%@#{sql.gsub('@', '\@')}@", __FILE__, __LINE__)
-      end
-
       # Instantiates objects for all attribute classes that needs more than one constructor parameter. This is done
       # by calling new on the column type or aggregation type (through composed_of) object with these parameters.
       # So having the pairs written_on(1) = "2004", written_on(2) = "6", written_on(3) = "24", will instantiate

activerecord/lib/active_record/nested_attributes.rb

@@ -413,7 +413,7 @@ def assign_nested_attributes_for_collection_association(association_name, attrib
             if target_record
               existing_record = target_record
             else
-              association.send(:add_record_to_target_with_callbacks, existing_record)
+              association.send(:add_to_target, existing_record)
             end
           end
 

activerecord/test/cases/associations/eager_test.rb

@@ -668,6 +668,14 @@ def test_limited_eager_with_numeric_in_association
     assert_equal people(:david, :susan), Person.find(:all, :include => [:readers, :primary_contact, :number1_fan], :conditions => "number1_fans_people.first_name like 'M%'", :order => 'people.id', :limit => 2, :offset => 0)
   end
 
+  def test_preload_with_interpolation
+    post = Post.includes(:comments_with_interpolated_conditions).find(posts(:welcome).id)
+    assert_equal [comments(:greetings)], post.comments_with_interpolated_conditions
+
+    post = Post.joins(:comments_with_interpolated_conditions).find(posts(:welcome).id)
+    assert_equal [comments(:greetings)], post.comments_with_interpolated_conditions
+  end
+
   def test_polymorphic_type_condition
     post = Post.find(posts(:thinking).id, :include => :taggings)
     assert post.taggings.include?(taggings(:thinking_general))

activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb

@@ -72,7 +72,7 @@ class DeveloperWithCounterSQL < ActiveRecord::Base
     :join_table => "developers_projects",
     :association_foreign_key => "project_id",
     :foreign_key => "developer_id",
-    :counter_sql => 'SELECT COUNT(*) AS count_all FROM projects INNER JOIN developers_projects ON projects.id = developers_projects.project_id WHERE developers_projects.developer_id =#{id}'
+    :counter_sql => proc { "SELECT COUNT(*) AS count_all FROM projects INNER JOIN developers_projects ON projects.id = developers_projects.project_id WHERE developers_projects.developer_id =#{id}" }
 end
 
 class HasAndBelongsToManyAssociationsTest < ActiveRecord::TestCase

activerecord/test/cases/associations/has_many_associations_test.rb

@@ -279,7 +279,6 @@ def test_counting_non_existant_items_using_sql
 
   def test_counting_using_finder_sql
     assert_equal 2, Firm.find(4).clients_using_sql.count
-    assert_equal 2, Firm.find(4).clients_using_multiline_sql.count
   end
 
   def test_belongs_to_sanity

activerecord/test/cases/associations/has_many_through_associations_test.rb

@@ -711,4 +711,11 @@ def test_deleting_from_has_many_through_a_belongs_to_should_not_try_to_update_co
     post.author_addresses.delete(address)
     assert post[:author_count].nil?
   end
+
+  def test_interpolated_conditions
+    post = posts(:welcome)
+    assert !post.tags.empty?
+    assert_equal post.tags, post.interpolated_tags
+    assert_equal post.tags, post.interpolated_tags_2
+  end
 end

activerecord/test/cases/associations/has_one_associations_test.rb

@@ -243,6 +243,14 @@ def test_dependence_with_missing_association_and_nullify
     firm.destroy
   end
 
+  def test_finding_with_interpolated_condition
+    firm = Firm.find(:first)
+    superior = firm.clients.create(:name => 'SuperiorCo')
+    superior.rating = 10
+    superior.save
+    assert_equal 10, firm.clients_with_interpolated_conditions.first.rating
+  end
+
   def test_assignment_before_child_saved
     firm = Firm.find(1)
     firm.account = a = Account.new("credit_limit" => 1000)

activerecord/test/cases/base_test.rb

@@ -1295,12 +1295,6 @@ def test_count_with_join
     assert_equal res6, res7
   end
 
-  def test_interpolate_sql
-    assert_nothing_raised { Category.new.send(:interpolate_sql, 'foo@bar') }
-    assert_nothing_raised { Category.new.send(:interpolate_sql, 'foo bar) baz') }
-    assert_nothing_raised { Category.new.send(:interpolate_sql, 'foo bar} baz') }
-  end
-
   def test_scoped_find_conditions
     scoped_developers = Developer.send(:with_scope, :find => { :conditions => 'salary > 90000' }) do
       Developer.find(:all, :conditions => 'id < 5')

activerecord/test/cases/connection_pool_test.rb

@@ -6,6 +6,16 @@ class ConnectionPoolTest < ActiveRecord::TestCase
       def setup
         # Keep a duplicate pool so we do not bother others
         @pool = ConnectionPool.new ActiveRecord::Base.connection_pool.spec
+
+        if in_memory_db?
+          # Separate connections to an in-memory database create an entirely new database,
+          # with an empty schema etc, so we just stub out this schema on the fly.
+          @pool.with_connection do |connection|
+            connection.create_table :posts do |t|
+              t.integer :cololumn
+            end
+          end
+        end
       end
 
       def test_pool_caches_columns

activerecord/test/models/company.rb

@@ -48,19 +48,16 @@ class Firm < Company
   has_many :dependent_clients_of_firm, :foreign_key => "client_of", :class_name => "Client", :order => "id", :dependent => :destroy
   has_many :exclusively_dependent_clients_of_firm, :foreign_key => "client_of", :class_name => "Client", :order => "id", :dependent => :delete_all
   has_many :limited_clients, :class_name => "Client", :limit => 1
+  has_many :clients_with_interpolated_conditions, :class_name => "Client", :conditions => proc { "rating > #{rating}" }
   has_many :clients_like_ms, :conditions => "name = 'Microsoft'", :class_name => "Client", :order => "id"
   has_many :clients_like_ms_with_hash_conditions, :conditions => { :name => 'Microsoft' }, :class_name => "Client", :order => "id"
-  has_many :clients_using_sql, :class_name => "Client", :finder_sql => 'SELECT * FROM companies WHERE client_of = #{id}'
-  has_many :clients_using_multiline_sql, :class_name => "Client", :finder_sql => '
-  SELECT
-  companies.*
-  FROM companies WHERE companies.client_of = #{id}'
+  has_many :clients_using_sql, :class_name => "Client", :finder_sql => proc { "SELECT * FROM companies WHERE client_of = #{id}" }
   has_many :clients_using_counter_sql, :class_name => "Client",
-           :finder_sql  => 'SELECT * FROM companies WHERE client_of = #{id}',
-           :counter_sql => 'SELECT COUNT(*) FROM companies WHERE client_of = #{id}'
+           :finder_sql  => proc { "SELECT * FROM companies WHERE client_of = #{id} " },
+           :counter_sql => proc { "SELECT COUNT(*) FROM companies WHERE client_of = #{id}" }
   has_many :clients_using_zero_counter_sql, :class_name => "Client",
-           :finder_sql  => 'SELECT * FROM companies WHERE client_of = #{id}',
-           :counter_sql => 'SELECT 0 FROM companies WHERE client_of = #{id}'
+           :finder_sql  => proc { "SELECT * FROM companies WHERE client_of = #{id}" },
+           :counter_sql => proc { "SELECT 0 FROM companies WHERE client_of = #{id}" }
   has_many :no_clients_using_counter_sql, :class_name => "Client",
            :finder_sql  => 'SELECT * FROM companies WHERE client_of = 1000',
            :counter_sql => 'SELECT COUNT(*) FROM companies WHERE client_of = 1000'

activerecord/test/models/post.rb

@@ -41,6 +41,9 @@ def find_most_recent
   has_many :author_categorizations, :through => :author, :source => :categorizations
   has_many :author_addresses, :through => :author
 
+  has_many :comments_with_interpolated_conditions, :class_name => 'Comment',
+    :conditions => proc { ["#{"#{aliased_table_name}." rescue ""}body = ?", 'Thank you for the welcome'] }
+
   has_one  :very_special_comment
   has_one  :very_special_comment_with_post, :class_name => "VerySpecialComment", :include => :post
   has_many :special_comments
@@ -57,6 +60,10 @@ def add_joins_and_select
     end
   end
 
+  has_many :interpolated_taggings, :class_name => 'Tagging', :as => :taggable, :conditions => proc { "1 = #{1}" }
+  has_many :interpolated_tags, :through => :taggings
+  has_many :interpolated_tags_2, :through => :interpolated_taggings, :source => :tag
+
   has_many :taggings_with_delete_all, :class_name => 'Tagging', :as => :taggable, :dependent => :delete_all
   has_many :taggings_with_destroy, :class_name => 'Tagging', :as => :taggable, :dependent => :destroy
 

activerecord/test/models/project.rb

@@ -7,14 +7,15 @@ class Project < ActiveRecord::Base
   has_and_belongs_to_many :developers_named_david, :class_name => "Developer", :conditions => "name = 'David'", :uniq => true
   has_and_belongs_to_many :developers_named_david_with_hash_conditions, :class_name => "Developer", :conditions => { :name => 'David' }, :uniq => true
   has_and_belongs_to_many :salaried_developers, :class_name => "Developer", :conditions => "salary > 0"
-  has_and_belongs_to_many :developers_with_finder_sql, :class_name => "Developer", :finder_sql => 'SELECT t.*, j.* FROM developers_projects j, developers t WHERE t.id = j.developer_id AND j.project_id = #{id} ORDER BY t.id'
-  has_and_belongs_to_many :developers_with_multiline_finder_sql, :class_name => "Developer", :finder_sql => '
-    SELECT
-      t.*, j.*
-    FROM
-      developers_projects j,
-      developers t WHERE t.id = j.developer_id AND j.project_id = #{id} ORDER BY t.id'
-  has_and_belongs_to_many :developers_by_sql, :class_name => "Developer", :delete_sql => "DELETE FROM developers_projects WHERE project_id = \#{id} AND developer_id = \#{record.id}"
+  has_and_belongs_to_many :developers_with_finder_sql, :class_name => "Developer", :finder_sql => proc { "SELECT t.*, j.* FROM developers_projects j, developers t WHERE t.id = j.developer_id AND j.project_id = #{id} ORDER BY t.id" }
+  has_and_belongs_to_many :developers_with_multiline_finder_sql, :class_name => "Developer", :finder_sql => proc {
+    "SELECT
+       t.*, j.*
+     FROM
+       developers_projects j,
+       developers t WHERE t.id = j.developer_id AND j.project_id = #{id} ORDER BY t.id"
+  }
+  has_and_belongs_to_many :developers_by_sql, :class_name => "Developer", :delete_sql => proc { |record| "DELETE FROM developers_projects WHERE project_id = #{id} AND developer_id = #{record.id}" }
   has_and_belongs_to_many :developers_with_callbacks, :class_name => "Developer", :before_add => Proc.new {|o, r| o.developers_log << "before_adding#{r.id || '<new>'}"},
                             :after_add => Proc.new {|o, r| o.developers_log << "after_adding#{r.id || '<new>'}"},
                             :before_remove => Proc.new {|o, r| o.developers_log << "before_removing#{r.id}"},

activerecord/test/models/tagging.rb

@@ -6,6 +6,7 @@ class Tagging < ActiveRecord::Base
   belongs_to :tag, :include => :tagging
   belongs_to :super_tag,   :class_name => 'Tag', :foreign_key => 'super_tag_id'
   belongs_to :invalid_tag, :class_name => 'Tag', :foreign_key => 'tag_id'
+  belongs_to :interpolated_tag, :class_name => 'Tag', :foreign_key => :tag_id, :conditions => proc { "1 = #{1}" }
   belongs_to :taggable, :polymorphic => true, :counter_cache => true
   has_many :things, :through => :taggable
 end