Permit ActionController::AnyParam on hashes

lib/action_controller/parameters.rb

@@ -27,6 +27,8 @@ def initialize(params)
     end
   end
 
+  class AnyParam; end
+
   class Parameters < ActiveSupport::HashWithIndifferentAccess
     attr_accessor :permitted
     alias :permitted? :permitted
@@ -191,6 +193,11 @@ def hash_filter(params, filter)
         slice(*filter.keys).each do |key, value|
           next unless value
 
+          if filter[key] == ActionController::AnyParam
+            params[key] = value
+            return
+          end
+
           if filter[key] == []
             # Declaration {:comment_ids => []}.
             array_of_permitted_scalars_filter(params, key)

test/parameters_permit_test.rb

@@ -346,4 +346,48 @@ def assert_filtered_out(params, key)
       assert !hash.permitted?
     end
   end
+
+  test 'any param permitted in the root' do
+    initial_hash = {
+      :book => {
+        :title => "Romeo and Juliet",
+        :authors => [{
+          :name => "William Shakespeare",
+          :born => "1564-04-26"
+        }]
+      }
+    }
+
+    params = ActionController::Parameters.new(initial_hash)
+
+    permitted = params.permit({ :book => ActionController::AnyParam })
+    assert_equal initial_hash.with_indifferent_access, permitted
+  end
+
+  test 'any param permitted in a nested hash' do
+    initial_hash = {
+      :book => {
+        :title => "Romeo and Juliet",
+        :authors => [{
+          :name => "William Shakespeare",
+          :born => "1564-04-26"
+        }]
+      }
+    }
+
+    params = ActionController::Parameters.new(initial_hash)
+    expected_hash = {
+      "book" => {
+        "authors" => [
+          {
+            "name" =>  "William Shakespeare",
+            "born" => "1564-04-26"
+          }
+        ]
+      }
+    }
+
+    permitted = params.permit({ :book => [ authors: ActionController::AnyParam ] })
+    assert_equal expected_hash, permitted
+  end
 end