Merge branch 'master' into treewip

* master: (113 commits)
  remove useless method
  Updated file documentation [ci skip]
  changes caching guide to add note on weak etags
  Don't put config.action_mailer.perform_caching entry twice in development.rb
  Fix wording and wrong reference
  Add Ruby formatting to CHANGELOG entry
  Fix ActionView's cache section reference
  Do not define methods in the included block
  Add caching guide in ActionMailer basics
  Add ActionMailer configuration options
  Preparing for 5.0.0.beta3 release
  Update 5.0 release notes
  Enable tmp_restart plugin for puma
  Prep release for Rails 5 beta3
  [ci skip] Move collection caching changelog entry.
  Ensure `drop_table` even if tests failure or interrupted
  :bomb: run the test @rafaelfranca :angry:
  Remove changelog entry for reverted commit
  Add CHANGELOG for https://github.com/rails/rails/pull/23734 [ci skip]
  No need CHANGELOG entry for #23849.
  ...

1 files changed, 1 insertions, 0 deletions

diff --git a/actionpack/lib/action_dispatch/middleware/params_parser.rb b/actionpack/lib/action_dispatch/middleware/params_parser.rb
index c2a4f46e67..5841c978af 100644
--- a/actionpack/lib/action_dispatch/middleware/params_parser.rb
+++ b/actionpack/lib/action_dispatch/middleware/params_parser.rb
@@ -37,6 +37,7 @@ module ActionDispatch
     # The +parsers+ argument can take Hash of parsers where key is identifying
     # content mime type, and value is a lambda that is going to process data.
     def self.new(app, parsers = {})
+      parsers = parsers.transform_keys { |key| key.respond_to?(:symbol) ? key.symbol : key }
       ActionDispatch::Request.parameter_parsers = ActionDispatch::Request::DEFAULT_PARSERS.merge(parsers)
       app
     end