OptionParser#on with non-option Regexp causes invalid options to be duplicated

[postmodern]

I discovered this unexpected behavior which may be a bug in OptionParser. When an OptionParser is defined with an .on(/^[^-].*$/) { |arg| ... } to catch all non-option arguments, it causes invalid option arguments to be duplicated or doubled. When the on(...) callback is removed, the invalid options are not doubled or duplicated.

Example (with .on(/.../))

#!/usr/bin/env ruby

require 'optparse'

optparser = OptionParser.new do |opts|
  opts.on(/^[^-].*$/) do |arg|
    puts "Never gets called"
  end
end

begin
  optparser.parse(ARGV)
rescue OptionParser::ParseError => error
  $stderr.puts "error: #{error.message}"
  $stderr.puts "args: #{error.args.inspect}"
end

Output

$ ./test.rb -t
error: invalid option: -t -t
args: ["-t", "-t"]

Example (without .on(/.../))

#!/usr/bin/env ruby

require 'optparse'

optparser = OptionParser.new do |opts|
end

begin
  optparser.parse(ARGV)
rescue OptionParser::ParseError => error
  $stderr.puts "error: #{error.message}"
  $stderr.puts "args: #{error.args.inspect}"
end

Output

$ ./test.rb -t
error: invalid option -t
args: ["-t"]

Tested With

• optparse (default: 0.1.0)
• ruby 3.0.0p0 (2020-12-25 revision 95aff21468) [x86_64-linux]
• ruby 2.7.2p137 (2020-10-01 revision 5445e04352) [x86_64-linux]