Merge pull request #1137 from aselder/fix-frozen-string-send-file

Don't blow up when passing frozen string to send_file disposition.

lib/sinatra/base.rb

@@ -360,7 +360,7 @@ def content_type(type = nil, params = {})
     # Set the Content-Disposition to "attachment" with the specified filename,
     # instructing the user agents to prompt to save.
     def attachment(filename = nil, disposition = :attachment)
-      response['Content-Disposition'] = disposition.to_s
+      response['Content-Disposition'] = disposition.to_s.dup
       if filename
         params = '; filename="%s"' % File.basename(filename)
         response['Content-Disposition'] << params

test/helpers_test.rb

@@ -879,6 +879,12 @@ def send_file_app(opts={})
       assert_equal 'inline; filename="file.txt"', response['Content-Disposition']
     end
 
+    it "does not raise an error when :disposition set to a frozen string" do
+      send_file_app :disposition => 'inline'.freeze
+      get '/file.txt'
+      assert_equal 'inline; filename="file.txt"', response['Content-Disposition']
+    end 
+
     it "sets the Content-Disposition header when :filename provided" do
       send_file_app :filename => 'foo.txt'
       get '/file.txt'