Trust `Object#dup` in `ActionController::Parameters`, using `#initialize_copy` to manually duplicate the underlying parameters hash

It looks like `ActionController::Parameters#dup` is leftover from when the class inherited from `Hash`. We can just trust `#dup`, which already copies the `@permitted` instance variable (confirmed by tests). We still define a `#initialize_copy` to make `@parameters` a copy that can be mutated without affecting the original instance.

1 files changed, 1 insertions, 15 deletions

diff --git a/actionpack/lib/action_controller/metal/strong_parameters.rb b/actionpack/lib/action_controller/metal/strong_parameters.rb
index fea04d98e0..26794c67b7 100644
--- a/actionpack/lib/action_controller/metal/strong_parameters.rb
+++ b/actionpack/lib/action_controller/metal/strong_parameters.rb
@@ -572,20 +572,6 @@ module ActionController
       convert_value_to_parameters(@parameters.values_at(*keys))
     end
 
-    # Returns an exact copy of the <tt>ActionController::Parameters</tt>
-    # instance. +permitted+ state is kept on the duped object.
-    #
-    #   params = ActionController::Parameters.new(a: 1)
-    #   params.permit!
-    #   params.permitted?        # => true
-    #   copy_params = params.dup # => <ActionController::Parameters {"a"=>1} permitted: true>
-    #   copy_params.permitted?   # => true
-    def dup
-      super.tap do |duplicate|
-        duplicate.permitted = @permitted
-      end
-    end
-
     # Returns a new <tt>ActionController::Parameters</tt> with all keys from
     # +other_hash+ merges into current hash.
     def merge(other_hash)
@@ -786,7 +772,7 @@ module ActionController
 
       def initialize_copy(source)
         super
-        @parameters = source.instance_variable_get(:@parameters).dup
+        @parameters = @parameters.dup
       end
   end