scope_chain should not be mutated for other reflections

Currently `scope_chain` uses same array for building different
`scope_chain` for different associations. During processing
these arrays are sometimes mutated and because of in-place
mutation the changed `scope_chain` impacts other reflections.

Fix is to dup the value before adding to the `scope_chain`.

Fixes #3882.

1 files changed, 16 insertions, 0 deletions

diff --git a/activerecord/test/cases/reflection_test.rb b/activerecord/test/cases/reflection_test.rb
index 0e5c7df2cc..d7ad5ed29f 100644
--- a/activerecord/test/cases/reflection_test.rb
+++ b/activerecord/test/cases/reflection_test.rb
@@ -18,6 +18,11 @@ require 'models/subscription'
 require 'models/tag'
 require 'models/sponsor'
 require 'models/edge'
+require 'models/hotel'
+require 'models/chef'
+require 'models/department'
+require 'models/cake_designer'
+require 'models/drink_designer'
 
 class ReflectionTest < ActiveRecord::TestCase
   include ActiveRecord::Reflection
@@ -227,6 +232,17 @@ class ReflectionTest < ActiveRecord::TestCase
     assert_equal expected, actual
   end
 
+  def test_scope_chain_does_not_interfere_with_hmt_with_polymorphic_case
+    @hotel = Hotel.create!
+    @department = @hotel.departments.create!
+    @department.chefs.create!(employable: CakeDesigner.create!)
+    @department.chefs.create!(employable: DrinkDesigner.create!)
+
+    assert_equal 1, @hotel.cake_designers.size
+    assert_equal 1, @hotel.drink_designers.size
+    assert_equal 2, @hotel.chefs.size
+  end
+
   def test_nested?
     assert !Author.reflect_on_association(:comments).nested?
     assert Author.reflect_on_association(:tags).nested?