fix association :extend option

activerecord/lib/active_record/associations/association_scope.rb

@@ -15,9 +15,7 @@ def initialize(association)
 
       def scope
         scope = klass.unscoped
-        scope.extending!(*Array(options[:extend]))
         scope.merge! eval_scope(klass, reflection.scope) if reflection.scope
-
         add_constraints(scope)
       end
 
@@ -120,10 +118,8 @@ def table_name_for(reflection)
       end
 
       def eval_scope(klass, scope)
-        return scope if scope.is_a?(Relation)
-
-        if scope.arity == 0
-          klass.unscoped.instance_exec(&scope)
+        if scope.is_a?(Relation)
+          scope
         else
           klass.unscoped.instance_exec(owner, &scope)
         end

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

@@ -23,6 +23,11 @@ def initialize(model, name, scope, options)
         @scope   = nil
         @options = scope
       end
+
+      if @scope && @scope.arity == 0
+        prev_scope = @scope
+        @scope = proc { instance_exec(&prev_scope) }
+      end
     end
 
     def mixin

activerecord/lib/active_record/associations/builder/collection_association.rb

@@ -6,7 +6,7 @@ def valid_options
       super + [:table_name, :finder_sql, :counter_sql, :before_add, :after_add, :before_remove, :after_remove]
     end
 
-    attr_reader :block_extension
+    attr_reader :block_extension, :extension_module
 
     def initialize(*args, &extension)
       super(*args)
@@ -27,18 +27,24 @@ def writable?
     private
 
       def wrap_block_extension
-        options[:extend] = Array(options[:extend])
-
         if block_extension
+          @extension_module = mod = Module.new(&block_extension)
           silence_warnings do
-            model.parent.const_set(extension_module_name, Module.new(&block_extension))
+            model.parent.const_set(extension_module_name, mod)
+          end
+
+          prev_scope = @scope
+
+          if prev_scope
+            @scope = proc { |owner| instance_exec(owner, &prev_scope).extending(mod) }
+          else
+            @scope = proc { extending(mod) }
           end
-          options[:extend].push("#{model.parent}::#{extension_module_name}".constantize)
         end
       end
 
       def extension_module_name
-        @extension_module_name ||= "#{model.to_s.demodulize}#{name.to_s.camelize}AssociationExtension"
+        @extension_module_name ||= "#{model.name.demodulize}#{name.to_s.camelize}AssociationExtension"
       end
 
       def define_callback(callback_name)

activerecord/lib/active_record/relation/query_methods.rb

@@ -529,7 +529,7 @@ def extending(*modules, &block)
     def extending!(*modules, &block)
       modules << Module.new(&block) if block_given?
 
-      self.extending_values = modules.flatten
+      self.extending_values += modules.flatten
       extend(*extending_values) if extending_values.any?
 
       self

activerecord/test/cases/associations/extension_test.rb

@@ -72,6 +72,6 @@ def test_proxy_association_after_scoped
     def extension_name(model)
       builder = ActiveRecord::Associations::Builder::HasMany.new(model, :association_name, nil, {}) { }
       builder.send(:wrap_block_extension)
-      builder.options[:extend].first.name
+      builder.extension_module.name
     end
 end

activerecord/test/cases/relation_test.rb

@@ -191,11 +191,14 @@ def relation
     end
 
     test 'extending!' do
-      mod = Module.new
+      mod, mod2 = Module.new, Module.new
 
       assert relation.extending!(mod).equal?(relation)
-      assert [mod], relation.extending_values
+      assert_equal [mod], relation.extending_values
       assert relation.is_a?(mod)
+
+      relation.extending!(mod2)
+      assert_equal [mod, mod2], relation.extending_values
     end
 
     test 'extending! with empty args' do