1 files changed, 31 insertions, 24 deletions

diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index 73baefb8e1..175019a72b 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -12,17 +12,18 @@ module ActiveRecord
         @through_association = nil
       end
 
-      # Returns the size of the collection by executing a SELECT COUNT(*) query if the collection hasn't been
-      # loaded and calling collection.size if it has. If it's more likely than not that the collection does
-      # have a size larger than zero, and you need to fetch that collection afterwards, it'll take one fewer
-      # SELECT query if you use #length.
+      # Returns the size of the collection by executing a SELECT COUNT(*) query
+      # if the collection hasn't been loaded, and by calling collection.size if
+      # it has. If the collection will likely have a size greater than zero,
+      # and if fetching the collection will be needed afterwards, one less
+      # SELECT query will be generated by using #length instead.
       def size
         if has_cached_counter?
           owner.read_attribute cached_counter_attribute_name(reflection)
         elsif loaded?
           target.size
         else
-          count
+          super
         end
       end
 
@@ -72,25 +73,27 @@ module ActiveRecord
           @through_association ||= owner.association(through_reflection.name)
         end
 
-        # We temporarily cache through record that has been build, because if we build a
-        # through record in build_record and then subsequently call insert_record, then we
-        # want to use the exact same object.
+        # The through record (built with build_record) is temporarily cached
+        # so that it may be reused if insert_record is subsequently called.
         #
-        # However, after insert_record has been called, we clear the cache entry because
-        # we want it to be possible to have multiple instances of the same record in an
-        # association
+        # However, after insert_record has been called, the cache is cleared in
+        # order to allow multiple instances of the same record in an association.
         def build_through_record(record)
           @through_records[record.object_id] ||= begin
             ensure_mutable
 
-            through_record = through_association.build through_scope_attributes
+            through_record = through_association.build(*options_for_through_record)
             through_record.send("#{source_reflection.name}=", record)
             through_record
           end
         end
 
+        def options_for_through_record
+          [through_scope_attributes]
+        end
+
         def through_scope_attributes
-          scope.where_values_hash(through_association.reflection.name.to_s)
+          scope.where_values_hash(through_association.reflection.name.to_s).except!(through_association.reflection.foreign_key)
         end
 
         def save_through_record(record)
@@ -106,9 +109,9 @@ module ActiveRecord
 
           inverse = source_reflection.inverse_of
           if inverse
-            if inverse.macro == :has_many
+            if inverse.collection?
               record.send(inverse.name) << build_through_record(record)
-            elsif inverse.macro == :has_one
+            elsif inverse.has_one?
               record.send("#{inverse.name}=", build_through_record(record))
             end
           end
@@ -117,7 +120,7 @@ module ActiveRecord
         end
 
         def target_reflection_has_associated_record?
-          !(through_reflection.macro == :belongs_to && owner[through_reflection.foreign_key].blank?)
+          !(through_reflection.belongs_to? && owner[through_reflection.foreign_key].blank?)
         end
 
         def update_through_counter?(method)
@@ -131,13 +134,13 @@ module ActiveRecord
           end
         end
 
+        def delete_or_nullify_all_records(method)
+          delete_records(load_target, method)
+        end
+
         def delete_records(records, method)
           ensure_not_nested
 
-          # This is unoptimised; it will load all the target records
-          # even when we just want to delete everything.
-          records = load_target if records == :all
-
           scope = through_association.scope
           scope.where! construct_join_attributes(*records)
 
@@ -171,7 +174,7 @@ module ActiveRecord
             klass.decrement_counter counter, records.map(&:id)
           end
 
-          if through_reflection.macro == :has_many && update_through_counter?(method)
+          if through_reflection.collection? && update_through_counter?(method)
             update_counter(-count, through_reflection)
           end
 
@@ -181,14 +184,18 @@ module ActiveRecord
         def through_records_for(record)
           attributes = construct_join_attributes(record)
           candidates = Array.wrap(through_association.target)
-          candidates.find_all { |c| c.attributes.slice(*attributes.keys) == attributes }
+          candidates.find_all do |c|
+            attributes.all? do |key, value|
+              c.public_send(key) == value
+            end
+          end
         end
 
         def delete_through_records(records)
           records.each do |record|
             through_records = through_records_for(record)
 
-            if through_reflection.macro == :has_many
+            if through_reflection.collection?
               through_records.each { |r| through_association.target.delete(r) }
             else
               if through_records.include?(through_association.target)
@@ -202,7 +209,7 @@ module ActiveRecord
 
         def find_target
           return [] unless target_reflection_has_associated_record?
-          scope.to_a
+          get_records
         end
 
         # NOTE - not sure that we can actually cope with inverses here