do not call super in Response#finish to avoid infinite loop or body proxy

lib/sinatra/base.rb

@@ -78,19 +78,39 @@ module Sinatra
     end
 
     def finish
-      if status.to_i / 100 == 1
+      result = body
+
+      if drop_content_info?
         headers.delete "Content-Length"
         headers.delete "Content-Type"
-      elsif Array === body and not [204, 205, 304].include?(status.to_i)
-        # if some other code has already set Content-Length, don't muck with it
-        # currently, this would be the static file-handler
-        headers["Content-Length"] ||= body.inject(0) { |l, p| l + Rack::Utils.bytesize(p) }.to_s
       end
 
-      # Rack::Response#finish sometimes returns self as response body. We don't want that.
-      status, headers, result = super
-      result = body if result == self || Rack::BodyProxy === result
-      [status, headers, result]
+      if drop_body?
+        close
+        result = []
+      end
+
+      if calculate_content_length?
+        # if some other code has already set Content-Length, don't muck with it
+        # currently, this would be the static file-handler
+        headers["Content-Length"] = body.inject(0) { |l, p| l + Rack::Utils.bytesize(p) }.to_s
+      end
+
+      [status.to_i, header, result]
+    end
+
+    private
+
+    def calculate_content_length?
+      headers["Content-Type"] and not headers["Content-Length"] and Array === body
+    end
+
+    def drop_content_info?
+      status.to_i / 100 == 1 or drop_body?
+    end
+
+    def drop_body?
+      [204, 205, 304].include?(status.to_i)
     end
   end