build scope chain functionally and remove caching

This commit walks the reflection tree and builds the scope chain
functionally.  It also removes the chain cache since the cache doesn't
seem to have any impact on performance (I'd prefer to only cache at
proven bottlenecks)

1 files changed, 40 insertions, 14 deletions

diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index 99c0e71f97..956fe7c51e 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -239,6 +239,10 @@ module ActiveRecord
       def alias_candidate(name)
         "#{plural_name}_#{name}"
       end
+
+      def chain
+        collect_join_chain
+      end
     end
 
     # Base class for AggregateReflection and AssociationReflection. Objects of
@@ -421,7 +425,7 @@ module ActiveRecord
 
       # A chain of reflections from this one back to the owner. For more see the explanation in
       # ThroughReflection.
-      def chain
+      def collect_join_chain
         [self]
       end
 
@@ -495,6 +499,18 @@ module ActiveRecord
       VALID_AUTOMATIC_INVERSE_MACROS = [:has_many, :has_one, :belongs_to]
       INVALID_AUTOMATIC_INVERSE_OPTIONS = [:conditions, :through, :polymorphic, :foreign_key]
 
+      def add_as_source(seed)
+        seed
+      end
+
+      def add_as_polymorphic_through(reflection, seed)
+        seed + [PolymorphicReflection.new(self, reflection)]
+      end
+
+      def add_as_through(seed)
+        seed + [self]
+      end
+
       protected
 
         def actual_source_reflection # FIXME: this is a horrible name
@@ -742,19 +758,8 @@ module ActiveRecord
       #   # => [<ActiveRecord::Reflection::ThroughReflection: @delegate_reflection=#<ActiveRecord::Reflection::HasManyReflection: @name=:tags...>,
       #         <ActiveRecord::Reflection::HasManyReflection: @name=:taggings, @options={}, @active_record=Post>]
       #
-      def chain
-        @chain ||= begin
-          a = source_reflection.chain
-          b = through_reflection.chain.map(&:dup)
-
-          if options[:source_type]
-            b[0] = PolymorphicReflection.new(b[0], self)
-          end
-
-          chain = a + b
-          chain[0] = self # Use self so we don't lose the information from :source_type
-          chain
-        end
+      def collect_join_chain
+        collect_join_reflections [self]
       end
 
       # This is for clearing cache on the reflection. Useful for tests that need to compare
@@ -913,6 +918,27 @@ module ActiveRecord
         scope_chain
       end
 
+      def add_as_source(seed)
+        collect_join_reflections seed
+      end
+
+      def add_as_polymorphic_through(reflection, seed)
+        collect_join_reflections(seed + [PolymorphicReflection.new(self, reflection)])
+      end
+
+      def add_as_through(seed)
+        collect_join_reflections(seed + [self])
+      end
+
+      def collect_join_reflections(seed)
+        a = source_reflection.add_as_source seed
+        if options[:source_type]
+          through_reflection.add_as_polymorphic_through self, a
+        else
+          through_reflection.add_as_through a
+        end
+      end
+
       protected
 
         def actual_source_reflection # FIXME: this is a horrible name