First of all in my tests the errors are only triggered when calling .each, not in the constructor so this:

require "getoptlong"

GetoptLong.new(
  [ "--argument", "-a", GetoptLong::REQUIRED_ARGUMENT ]
)

# ~$ ruby script.rb --argument

Doesn’t show any error.

This shows the error:

require "getoptlong"

GetoptLong.new(
  [ "--argument", "-a", GetoptLong::REQUIRED_ARGUMENT ]
).each

# ~$ ruby script.rb --argument

Error:

test_getoptlong.rb: option `--argument' requires an argument
/Users/me/.rbenv/versions/3.1.1/lib/ruby/3.1.0/getoptlong.rb:398:in `set_error': option `--argument' requires an argument (GetoptLong::MissingArgument)

If I don’t pass the argument --argument at all, I don’t see any error:

require "getoptlong"

GetoptLong.new(
  [ "--argument", "-a", GetoptLong::REQUIRED_ARGUMENT ]
).each

# ~$ ruby script.rb

No error.

As this is a GetoptLong::REQUIRED_ARGUMENT, I expected to see an error if the user didn’t add it to the script call.

How can I raise an error if any GetoptLong::REQUIRED_ARGUMENT is missing?