Allow parameter filters to match multi-parameter attributes

lib/action_controller/parameters.rb

@@ -29,7 +29,7 @@ def permit!
     def require(key)
       self[key].presence || raise(ActionController::ParameterMissing.new(key))
     end
-    
+
     alias :required :require
 
     def permit(*filters)
@@ -39,6 +39,10 @@ def permit(*filters)
         case filter
         when Symbol then
           params[filter] = self[filter] if has_key?(filter)
+
+          multi_param_keys_for(filter).each do |multi_filter|
+            params[multi_filter] = self[multi_filter]
+          end
         when Hash then
           self.slice(*filter.keys).each do |key, value|
             return unless value
@@ -97,6 +101,12 @@ def each_element(object)
           yield object
         end
       end
+
+      def multi_param_keys_for(filter)
+        keys.select { |key|
+          key.index("#{filter}(") == 0 && key.index(")") == key.length - 1
+        }
+      end
   end
 
   module StrongParameters

test/multi_parameter_attributes_test.rb

@@ -0,0 +1,33 @@
+require 'test_helper'
+require 'action_controller/parameters'
+
+class MultiParameterAttributesTest < ActiveSupport::TestCase
+  test "permitted multi-parameter attribute keys" do
+    params = ActionController::Parameters.new({
+      book: {
+        "shipped_at(1i)" => "2012",
+        "shipped_at(2i)" => "3",
+        "shipped_at(3i)" => "25",
+        "shipped_at(4i)" => "10",
+        "shipped_at(5i)" => "15",
+        "published_at(1i)"   => "1999",
+        "published_at(2i)"   => "2",
+        "published_at(3i)"   => "5"
+      }
+    })
+
+    permitted = params.permit book: [ :shipped_at ]
+
+    assert permitted.permitted?
+
+    assert_equal "2012", permitted[:book]["shipped_at(1i)"]
+    assert_equal "3", permitted[:book]["shipped_at(2i)"]
+    assert_equal "25", permitted[:book]["shipped_at(3i)"]
+    assert_equal "10", permitted[:book]["shipped_at(4i)"]
+    assert_equal "15", permitted[:book]["shipped_at(5i)"]
+
+    assert_nil permitted[:book]["published_at(1i)"]
+    assert_nil permitted[:book]["published_at(2i)"]
+    assert_nil permitted[:book]["published_at(3i)"]
+  end
+end