eliminate the `loaded?` conditional

activerecord/lib/active_record/associations/preloader.rb

@@ -174,14 +174,18 @@ def association_klass(reflection, record)
       end
 
       class NullPreloader
-        attr_reader :owners
+        attr_reader :owners, :reflection
 
         def initialize(klass, owners, reflection, preload_scope)
           @owners = owners
+          @reflection = reflection
         end
 
         def run(preloader); end
-        def loaded?; false; end
+
+        def preloaded_records
+          owners.flat_map { |owner| owner.read_attribute reflection.name }
+        end
       end
 
       def preloader_for(reflection, owners)

activerecord/lib/active_record/associations/preloader/association.rb

@@ -17,7 +17,6 @@ def initialize(klass, owners, reflection, preload_scope)
           @owners_by_key = nil
           @type_caster   = IDENTITY_CASTER
           @associated_records_by_owner = nil
-          @loaded = false
         end
 
         def run(preloader)
@@ -74,15 +73,9 @@ def preloaded_records
           @associated_records_by_owner.values.flatten
         end
 
-        def loaded?
-          @loaded
-        end
-
         private
 
         def associated_records_by_owner(preloader)
-          @loaded = true
-
           return @associated_records_by_owner if @associated_records_by_owner
 
           owners_map = owners_by_key

activerecord/lib/active_record/associations/preloader/through_association.rb

@@ -12,8 +12,6 @@ def source_reflection
         end
 
         def associated_records_by_owner(preloader)
-          @loaded = true
-
           return @associated_records_by_owner if @associated_records_by_owner
 
           preloader.preload(owners,
@@ -54,7 +52,7 @@ def associated_records_by_owner(preloader)
                 r.send(source_reflection.name)
               }.compact
 
-              if pl && pl.loaded?
+              if pl
                 loaded_records = pl.preloaded_records
                 i = 0
                 record_index = loaded_records.each_with_object({}) { |r,indexes|