-N, --[no-]line-numbers option doesn't seem to be working

[bartpiet]

Running rdoc executable with --line-numbers option doesn't cause numbers of individual lines to be included in source code fragments.

rdoc --line-numbers ./lib/*.rb

Sample source fragment in generated HTML looks like this:

# File lib/nanorm/connection.rb, line 15
def execute(query)
  self.handler.query(query)
end

while it's reasonable to assume it should look like this:

   # File lib/nanorm/connection.rb
15 def execute(query)
16   self.handler.query(query)
17 end

No error message or warning is displayed in CLI. I'm using RDoc 6.0.1 on Ruby 2.5.0 (x86_64-linux). The second sample was in fact generated after editing generator/markup.rb in RDoc source and setting RDoc::MethodAttr.add_line_numbers variable to true. The feature is implemented and seems to be working fine, but for some reason it's inaccessible because the option is ignored.

Am I missing something? I looked for issues regarding this option, but haven't found any. Also, I checked with some earlier versions, 3.9.5 and 4.1.0 (on Ruby 1.9.3 and 2.1.10 respectively) behave the same way. RDoc V1.0.1 on Ruby 1.8.7 handles the option correctly.