Allow filtering params based on parent keys

Add the possibility to only filter parameters based on
their full path instead of relying on the immediate key.

    config.filter_parameters += ['credit_card.code']

    { 'credit_card' => { 'code' => '[FILTERED]' },
      'source' => { 'code' => '<%= puts 5 %>' } }

actionpack/lib/action_dispatch/http/parameter_filter.rb

@@ -30,31 +30,39 @@ def self.compile(filters)
             when Regexp
               regexps << item
             else
-              strings << item.to_s
+              strings << Regexp.escape(item.to_s)
             end
           end
 
+          deep_regexps, regexps = regexps.partition { |r| r.to_s.include?("\\.") }
+          deep_strings, strings = strings.partition { |s| s.include?("\\.") }
+
           regexps << Regexp.new(strings.join('|'), true) unless strings.empty?
-          new regexps, blocks
+          deep_regexps << Regexp.new(deep_strings.join('|'), true) unless deep_strings.empty?
+
+          new regexps, deep_regexps, blocks
         end
 
-        attr_reader :regexps, :blocks
+        attr_reader :regexps, :deep_regexps, :blocks
 
-        def initialize(regexps, blocks)
+        def initialize(regexps, deep_regexps, blocks)
           @regexps = regexps
+          @deep_regexps = deep_regexps.any? ? deep_regexps : nil
           @blocks  = blocks
         end
 
-        def call(original_params)
+        def call(original_params, parents = [])
           filtered_params = {}
 
           original_params.each do |key, value|
             if regexps.any? { |r| key =~ r }
               value = FILTERED
+            elsif deep_regexps && (joined = (parents + [key]).join('.')) && deep_regexps.any? { |r| joined =~ r }
+              value = FILTERED
             elsif value.is_a?(Hash)
-              value = call(value)
+              value = call(value, (parents + [key]))
             elsif value.is_a?(Array)
-              value = value.map { |v| v.is_a?(Hash) ? call(v) : v }
+              value = value.map { |v| v.is_a?(Hash) ? call(v, (parents + [key])) : v }
             elsif blocks.any?
               key = key.dup
               value = value.dup if value.duplicable?

actionpack/test/dispatch/request_test.rb

@@ -923,6 +923,7 @@ class RequestParameterFilter < BaseRequestTest
     [{'foo'=>'bar', 'baz'=>'foo'},{'foo'=>'[FILTERED]', 'baz'=>'[FILTERED]'},%w'foo baz'],
     [{'bar'=>{'foo'=>'bar','bar'=>'foo'}},{'bar'=>{'foo'=>'[FILTERED]','bar'=>'foo'}},%w'fo'],
     [{'foo'=>{'foo'=>'bar','bar'=>'foo'}},{'foo'=>'[FILTERED]'},%w'f banana'],
+    [{'deep'=>{'cc'=>{'code'=>'bar','bar'=>'foo'},'ss'=>{'code'=>'bar'}}},{'deep'=>{'cc'=>{'code'=>'[FILTERED]','bar'=>'foo'},'ss'=>{'code'=>'bar'}}},%w'deep.cc.code'],
     [{'baz'=>[{'foo'=>'baz'}, "1"]}, {'baz'=>[{'foo'=>'[FILTERED]'}, "1"]}, [/foo/]]]
 
     test_hashes.each do |before_filter, after_filter, filter_words|