Make Relation#extending work like other value methods

activerecord/lib/active_record/relation.rb

@@ -8,7 +8,8 @@ class Relation
     JoinOperation = Struct.new(:relation, :join_class, :on)
 
     MULTI_VALUE_METHODS  = [:includes, :eager_load, :preload, :select, :group,
-                            :order, :joins, :where, :having, :bind, :references]
+                            :order, :joins, :where, :having, :bind, :references,
+                            :extending]
 
     SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :from, :reordering,
                             :reverse_order, :uniq, :create_with]
@@ -18,7 +19,7 @@ class Relation
     include FinderMethods, Calculations, SpawnMethods, QueryMethods, Batches, Explain, Delegation
 
     attr_reader :table, :klass, :loaded
-    attr_accessor :extensions, :default_scoped
+    attr_accessor :default_scoped
     alias :loaded? :loaded
     alias :default_scoped? :default_scoped
 
@@ -31,7 +32,7 @@ def initialize(klass, table)
 
       SINGLE_VALUE_METHODS.each {|v| instance_variable_set(:"@#{v}_value", nil)}
       MULTI_VALUE_METHODS.each {|v| instance_variable_set(:"@#{v}_values", [])}
-      @extensions = []
+
       @create_with_value = {}
     end
 

activerecord/lib/active_record/relation/merger.rb

@@ -26,7 +26,6 @@ def other_hash
         hash = {}
         Relation::MULTI_VALUE_METHODS.map  { |name| hash[name] = other.send("#{name}_values") }
         Relation::SINGLE_VALUE_METHODS.map { |name| hash[name] = other.send("#{name}_value")  }
-        hash[:extensions] = other.extensions
         hash
       end
     end
@@ -73,8 +72,7 @@ def merge_multi_values
           relation.order_values += values[:order]
         end
 
-        # Apply scope extension modules
-        relation.send :apply_modules, values[:extensions] if values[:extensions]
+        relation.extend(*values[:extending]) unless values[:extending].blank?
       end
 
       def merge_single_values

activerecord/lib/active_record/relation/query_methods.rb

@@ -10,7 +10,9 @@ module QueryMethods
                   :where_values, :having_values, :bind_values,
                   :limit_value, :offset_value, :lock_value, :readonly_value, :create_with_value,
                   :from_value, :reordering_value, :reverse_order_value,
-                  :uniq_value, :references_values
+                  :uniq_value, :references_values, :extending_values
+
+    alias extensions extending_values
 
     def includes(*args)
       args.empty? ? self : clone.includes!(*args)
@@ -353,7 +355,9 @@ def extending(*modules, &block)
     def extending!(*modules, &block)
       modules << Module.new(&block) if block_given?
 
-      self.send(:apply_modules, modules.flatten)
+      self.extending_values = modules.flatten
+      extend(*extending_values)
+
       self
     end
 
@@ -494,13 +498,6 @@ def build_select(arel, selects)
       end
     end
 
-    def apply_modules(modules)
-      unless modules.empty?
-        @extensions += modules
-        modules.each {|extension| extend(extension) }
-      end
-    end
-
     def reverse_sql_order(order_query)
       order_query = ["#{quoted_table_name}.#{quoted_primary_key} ASC"] if order_query.empty?
 

activerecord/lib/active_record/relation/spawn_methods.rb

@@ -40,8 +40,7 @@ def except(*skips)
         result.send(:"#{method}_value=", send(:"#{method}_value"))
       end
 
-      # Apply scope extension modules
-      result.send(:apply_modules, extensions)
+      result.extend(*extending_values) if extending_values.any?
 
       result
     end
@@ -65,8 +64,7 @@ def only(*onlies)
         result.send(:"#{method}_value=", send(:"#{method}_value"))
       end
 
-      # Apply scope extension modules
-      result.send(:apply_modules, extensions)
+      result.extend(*extending_values) if extending_values.any?
 
       result
     end

activerecord/test/cases/relation_test.rb

@@ -156,7 +156,7 @@ def relation
       @relation ||= Relation.new :a, :b
     end
 
-    (Relation::MULTI_VALUE_METHODS - [:references]).each do |method|
+    (Relation::MULTI_VALUE_METHODS - [:references, :extending]).each do |method|
       test "##{method}!" do
         assert relation.public_send("#{method}!", :foo).equal?(relation)
         assert_equal [:foo], relation.public_send("#{method}_values")
@@ -168,6 +168,14 @@ def relation
       assert relation.references_values.include?('foo')
     end
 
+    test 'extending!' do
+      mod = Module.new
+
+      assert relation.extending!(mod).equal?(relation)
+      assert [mod], relation.extending_values
+      assert relation.is_a?(mod)
+    end
+
     (Relation::SINGLE_VALUE_METHODS - [:lock, :reordering, :reverse_order, :create_with]).each do |method|
       test "##{method}!" do
         assert relation.public_send("#{method}!", :foo).equal?(relation)
@@ -195,13 +203,6 @@ def relation
       assert !relation.reverse_order_value
     end
 
-    test 'extending!' do
-      mod = Module.new
-
-      assert relation.extending!(mod).equal?(relation)
-      assert relation.is_a?(mod)
-    end
-
     test 'create_with!' do
       assert relation.create_with!(foo: 'bar').equal?(relation)
       assert_equal({foo: 'bar'}, relation.create_with_value)