requiredOption doesn't behave properly with default value

[michalciechan]

The code

program
  .requiredOption("-p --path <string>", "glob pattern of files/folders to delete", "../*")
  .parse(process.argv);

deleteFiles(program.path);

will run without the -p option set (because technically it has a value, default, but still) and delete whatever ../* resolves to.

I think requiredOption should either:

1. Not have a default value parameter and keep it's current behaviour as-is.
2. Accept a default value parameter but only use it if the option flag is set, i.e. using the above example node program.js won't run but node program.js -p will run with program.path == "../*" and of course node program.js -p /some/path/* will run with program.path == "/some/path/*"

[shadowspawn]

I considered default values when I was implementing requiredOption and wondered if the default value was ever useful. Basically, it is not useful to pass a hard-coded default with requiredOption.

The use case I came up with that persuaded me to keep default value is:

program
   .requiredOption('password <secret>', 'password, must be supplied or PASSWORD defined', process.env.PASSWORD);

I particularly like this as an elegant combination of requiredOption and environment variables for defining mandatory option values.

(For interest, a different but closely related issue got opened just yesterday: #1130. I'll be keeping an eye on how much confusion the current behaviour causes.)

[michalciechan]

If requiredOption would use the default value only when it would be used as a flag (--required-option) it could combine the best of both worlds:

• it would still be a required option, because the program won't run without it being specified
• environment variables, config files etc. could still be used, you'd just have to
  explicitly specify the required option

So no option - program doesn't run, option without value - use the default, option with value - use the value.

[shadowspawn]

By design and as documented, .requiredOption() works like .option() except for making the option required. So if you specify the flag for an option with a <required-value> then you must supply a value.

The behaviour you describe is what you might think happens for option with an [optional-value]:

.requiredOption("-p --path [string]", "glob pattern of files/folders to delete", "../*")

but in fact the default value is assigned when the option is not supplied, as before! That behaviour does not seem particularly useful , but it has always been like that so would be a big breaking change.

[shadowspawn]

An answer was provided, and no further activity in a month. Closing this as resolved.

Feel free to open a new issue if it comes up again, with new information and renewed interest.

[shadowspawn]

For interest, I noticed a similar issue against argparse where the reporter expected the current Commander behaviour: nodeca/argparse#148

[shadowspawn]

PR #1652 adds .preset() for specifying the argument to use when optional argument not supplied.

program
   .addOption(new Option("-p --path [string]", "glob pattern of files/folders to delete")
      .preset("../*")
      .makeOptionMandatory());