Triage: detecting missing or unknown commands

[shadowspawn]

What is the best way to test for missing or unknown commands? Is the existing support good enough?

Research prompted by Commander v4 which changes program.args and will break some client code which was dependent on the previous behaviour: #1048

Example of affected code: #7 (comment)

Related issues:

• Show help if no command was executed #7 Show help if no command was executed
• Support to know if any known command was processed, or any output written #240 Support to know if any known command was processed, or any output written
• How to detect an unsupported command? #338 How to detect an unsupported command? [git-style]
• running an unknown subcommand does not fail #432 running an unknown subcommand does not fail
• Show help when command is unknown #603 Show help when command is unknown
• Using sub-command always invokes *  #809 Using sub-command always invokes *
• argments are empty #940 argments are empty
• Throw error when no sub-command specified #942 Throw error when no sub-command specified
• It looks not way to know has action is run? #977 It looks not way to know has action is run?
• Top level command action does not work. #978 Top level command action does not work
• Passing command option leaves content in args #1032 Passing command option leaves content in args

[shadowspawn]

A direct test for no arguments at all (including options) is used in the README. This works the same in Commander v4.

if (!process.argv.slice(2).length) {
  program.outputHelp(make_red);
}

or without the slice:

if (process.argv.length < 3) {
  program.help();
}

or equivalently using `rawArgs:

if (program.rawArgs.length < 3) {
  program.help();
}

[shadowspawn]

The example code from the README for detected unknown commands (in a program using action handlers) works the same in Commander v4:

program.on('command:*', function () {
  console.error('Invalid command: %s\nSee --help for a list of available commands.', program.args.join(' '));
  process.exit(1);
});

[shadowspawn]

I am interested in adding more explicit support for testing for an unhandled command, which has not triggered any action handlers or external commands. This would implicitly cover both missing and unknown commands with a single test.

[shadowspawn]

By default, an unknown subcommand shows an error and a missing subcommand shows the help in the published pre-release of Commander v5.0.0 (#1163)