Merge pull request #11004 from fredwu/4-0-activemodel-inclusion-chain-fix

Fixed ActiveModel::Model's inclusion chain

Author: José Valim

activemodel/lib/active_model/model.rb

@@ -79,6 +79,8 @@ def initialize(params={})
       params.each do |attr, value|
         self.public_send("#{attr}=", value)
       end if params
+
+      super
     end
 
     # Indicates if the model is persisted. Default is +false+.

activemodel/test/cases/model_test.rb

@@ -3,7 +3,14 @@
 class ModelTest < ActiveModel::TestCase
   include ActiveModel::Lint::Tests
 
+  module DefaultValue
+    def initialize(*args)
+      @attr ||= 'default value'
+    end
+  end
+
   class BasicModel
+    include DefaultValue
     include ActiveModel::Model
     attr_accessor :attr
   end
@@ -29,4 +36,9 @@ def test_persisted_is_always_false
     object = BasicModel.new(:attr => "value")
     assert object.persisted? == false
   end
+
+  def test_mixin_inclusion_chain
+    object = BasicModel.new
+    assert_equal object.attr, 'default value'
+  end
 end