Make ActionDispatch::Request::Session#fetch behave like Hash#fetch

Session#fetch was mutating the session when given a default argument
and/or a block. Since Session duck-types as a Hash, it should behave
like one in these cases.

1 files changed, 2 insertions, 3 deletions

diff --git a/actionpack/test/dispatch/request/session_test.rb b/actionpack/test/dispatch/request/session_test.rb
index a244d1364c..df55fcc8bc 100644
--- a/actionpack/test/dispatch/request/session_test.rb
+++ b/actionpack/test/dispatch/request/session_test.rb
@@ -68,13 +68,12 @@ module ActionDispatch
         assert_equal '1', session.fetch(:one)
 
         assert_equal '2', session.fetch(:two, '2')
-        assert_equal '2', session.fetch(:two)
+        assert_nil session.fetch(:two, nil)
 
         assert_equal 'three', session.fetch(:three) {|el| el.to_s }
-        assert_equal 'three', session.fetch(:three)
 
         assert_raise KeyError do
-          session.fetch(:four)
+          session.fetch(:three)
         end
       end