The current code uses the same namespace for user specified options, user specified arguments, and command.Command internals. Opened this issue to collect the related issues found during triage.

Issues:

• Cannot name options/subcommands after commander public methods or JavaScript built-ins #19 Cannot name options/subcommands after commander public methods or JavaScript built-ins
• '--domain' option may cause problem #105 '--domain' option may cause problem
• Option values should not be added to the command instance. #183 Option values should not be added to the command instance.
• "name" option is broken as of 2.4.0 #284 "name" option is broken as of 2.4.0
• Bug and Design Flaw: Option "--opts" clashes with Command#opts function #334 Bug and Design Flaw: Option "--opts" clashes with Command#opts function
• Breaks when using "domain" as an option #370 Breaks when using "domain" as an option
• Command name "inspect" causes weird behaviour #377 Command name "inspect" causes weird behaviour
• argument 'once' (and probably others) cause naming collision #404 argument 'once' (and probably others) cause naming collision
• It causes unexpected result if arguments are the same as option name #483 It causes unexpected result if arguments are the same as option name
• Move parsed options into a data object #514 Move parsed options into a data object
• Using .name and .description has unexpected results. #516 Using .name and .description has unexpected results.
• program.opts() can be overridden by an option #584 program.opts() can be overridden by an option
• Error when option --alias is defined #592 Error when option --alias is defined
• Error when argument has same name as a flag #629 Error when argument has same name as a flag
• Options object is not strictly the user input #644 Options object is not strictly the user input
• Init value of option '--name' is a [Function] #648 Init value of option '--name' is a [Function]

Pull Requests:

• Data overload #515 Data overload
• Fix options key name conflict with commander object's' key #673 Fix options key name conflict with commander object's' key

Fixing this will be a major breaking change. To manage the disruption perhaps we can make a new approach opt-in (non-breaking), then make the new behaviour default (breaking), before finally deprecating the old behaviour.