set the configured #inheritance_column on #become (#7503)

I had to create a new table because I needed an STI table,
which does not have both a "type" and a "custom_type"

the test fails with:
  1) Error:
test_alt_becomes_works_with_sti(InheritanceTest):
NoMethodError: undefined method `type=' for #<Cabbage id: 1, name: "my cucumber", custom_type: "Cucumber">
    /Users/username/Projects/rails/activemodel/lib/active_model/attribute_methods.rb:432:in `method_missing'
    /Users/username/Projects/rails/activerecord/lib/active_record/attribute_methods.rb:100:in `method_missing'
    /Users/username/Projects/rails/activerecord/lib/active_record/persistence.rb:165:in `becomes'
    test/cases/inheritance_test.rb:134:in `test_becomes_works_with_sti'
    test/cases/inheritance_test.rb:140:in `test_alt_becomes_works_with_sti'

5 files changed, 38 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index ffb8513624..7bd65c180d 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -161,7 +161,7 @@ module ActiveRecord
       became.instance_variable_set("@new_record", new_record?)
       became.instance_variable_set("@destroyed", destroyed?)
       became.instance_variable_set("@errors", errors)
-      became.type = klass.name unless self.class.descends_from_active_record?
+      became.public_send("#{klass.inheritance_column}=", klass.name) unless self.class.descends_from_active_record?
       became
     end
 
diff --git a/activerecord/test/cases/inheritance_test.rb b/activerecord/test/cases/inheritance_test.rb
index e80259a7f1..cc9a93c16f 100644
--- a/activerecord/test/cases/inheritance_test.rb
+++ b/activerecord/test/cases/inheritance_test.rb
@@ -5,9 +5,10 @@ require 'models/post'
 require 'models/project'
 require 'models/subscriber'
 require 'models/teapot'
+require 'models/vegetables'
 
 class InheritanceTest < ActiveRecord::TestCase
-  fixtures :companies, :projects, :subscribers, :accounts
+  fixtures :companies, :projects, :subscribers, :accounts, :vegetables
 
   def test_class_with_store_full_sti_class_returns_full_name
     old = ActiveRecord::Base.store_full_sti_class
@@ -127,6 +128,13 @@ class InheritanceTest < ActiveRecord::TestCase
     switch_to_default_inheritance_column
   end
 
+  def test_alt_becomes_works_with_sti
+    vegetable = Vegetable.find(1)
+    assert_kind_of Vegetable, vegetable
+    cabbage = vegetable.becomes(Cabbage)
+    assert_kind_of Cabbage, cabbage
+  end
+
   def test_inheritance_find_all
     companies = Company.all.merge!(:order => 'id').to_a
     assert_kind_of Firm, companies[0], "37signals should be a firm"
diff --git a/activerecord/test/fixtures/vegetables.yml b/activerecord/test/fixtures/vegetables.yml
new file mode 100644
index 0000000000..82bd607701
--- /dev/null
+++ b/activerecord/test/fixtures/vegetables.yml
@@ -0,0 +1,9 @@
+first_cucumber:
+  id: 1
+  custom_type: Cucumber
+  name: 'my cucumber'
+
+first_cabbage:
+  id: 2
+  custom_type: Cabbage
+  name: 'my cabbage'
\ No newline at end of file
diff --git a/activerecord/test/models/vegetables.rb b/activerecord/test/models/vegetables.rb
new file mode 100644
index 0000000000..59cedfd9f5
--- /dev/null
+++ b/activerecord/test/models/vegetables.rb
@@ -0,0 +1,14 @@
+class Vegetable < ActiveRecord::Base
+
+  validates_presence_of :name
+
+  def self.inheritance_column
+    'custom_type'
+  end
+end
+
+class Cucumber < Vegetable
+end
+
+class Cabbage < Vegetable
+end
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index 7c45ca27c0..eae7a04157 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -184,6 +184,11 @@ ActiveRecord::Schema.define do
   add_index :companies, [:firm_id, :type, :rating, :ruby_type], :name => "company_index"
   add_index :companies, [:firm_id, :type], :name => "company_partial_index", :where => "rating > 10"
 
+  create_table :vegetables, :force => true do |t|
+    t.string :name
+    t.string :custom_type
+  end
+
   create_table :computers, :force => true do |t|
     t.integer :developer, :null => false
     t.integer :extendedWarranty, :null => false