Fix missing index when using timestamps with index

The `index` option used with `timestamps` should be passed to both
`column` definitions for `created_at` and `updated_at` rather than just
the first.

This was happening because `Hash#delete` is used to extract the `index`
option passed to `timestamps`, thereby mutating the `options` hash
in-place. Now take a copy of the `options` before deleting so that the
original is not modified.

1 files changed, 11 insertions, 0 deletions

diff --git a/activerecord/test/cases/timestamp_test.rb b/activerecord/test/cases/timestamp_test.rb
index 7c89b4b9e8..5dab32995c 100644
--- a/activerecord/test/cases/timestamp_test.rb
+++ b/activerecord/test/cases/timestamp_test.rb
@@ -446,6 +446,17 @@ class TimestampTest < ActiveRecord::TestCase
     toy = Toy.first
     assert_equal [:created_at, :updated_at], toy.send(:all_timestamp_attributes_in_model)
   end
+
+  def test_index_is_created_for_both_timestamps
+    ActiveRecord::Base.connection.create_table(:foos, force: true) do |t|
+      t.timestamps(:foos, null: true, index: true)
+    end
+
+    indexes = ActiveRecord::Base.connection.indexes('foos')
+    assert_equal ['created_at', 'updated_at'], indexes.flat_map(&:columns).sort
+  ensure
+    ActiveRecord::Base.connection.drop_table(:foos)
+  end
 end
 
 class TimestampsWithoutTransactionTest < ActiveRecord::TestCase