Revert "Convert StrongParameters cache to a hash. This fixes an unbounded"

We cannot cache keys because arrays are mutable. We rather want to cache
the arrays. This behaviour is tailor-made for the usage pattern strongs
params is designed for.

In a forthcoming commit I am going to add a test that covers why we need
to cache by value.

Every strong params instance has a live span of a request, the cache goes
away with the object. Since strong params have such a concrete intention,
it would be interesting to see if there are actually any real-world use
cases that are an actual leak, one that practically may matter.

I am not convinced that the theoretical leak has any practical consequences,
but if it can be shown there are, then I believe we should either get rid of
the cache (which is an optimization), or else wipe it in the mutating API.

This reverts commit e63be2769c039e4e9ada523a8497ce3206cc8a9b.

1 files changed, 1 insertions, 1 deletions

diff --git a/actionpack/test/controller/parameters/parameters_permit_test.rb b/actionpack/test/controller/parameters/parameters_permit_test.rb
index 1856ecd42b..33a91d72d9 100644
--- a/actionpack/test/controller/parameters/parameters_permit_test.rb
+++ b/actionpack/test/controller/parameters/parameters_permit_test.rb
@@ -169,7 +169,7 @@ class ParametersPermitTest < ActiveSupport::TestCase
 
   test 'arrays are converted at most once' do
     params = ActionController::Parameters.new(foo: [{}])
-    assert_same params[:foo], params[:foo]
+    assert params[:foo].equal?(params[:foo])
   end
 
   test "fetch doesnt raise ParameterMissing exception if there is a default" do