Commander.js: What's the meaning of 'true' here?

[ozbillwang]

I follow the sample and give a wrong drink

$ cat a.js
var program = require('commander');

program
  .version('0.1.0')
  .option('-s --size <size>', 'Pizza size', /^(large|medium|small)$/i, 'medium')
  .option('-d --drink [drink]', 'Drink', /^(coke|pepsi|izze)$/i)
  .parse(process.argv);

console.log(' size: %j', program.size);
console.log(' drink: %j', program.drink);

$ node a.js
 size: "medium"
 drink: undefined

$ node a.js -d abc
 size: "medium"
 drink: true

What's the meaning of true here?

How do I write code to identify, if drink's value is not coke|pepsi|izze, exit(-1).

[shadowspawn]

The true means drink was specified as an option, but with no (valid) value. Like calling:

node a.js -d

How do I write code to identify, if drink's value is not coke|pepsi|izze, exit(-1).

I suggest you don't use the pattern in the .option call and instead check the option value yourself after calling parse. I also suggest putting the allowed values in the description so it appears in the help.

[ozbillwang]

should we change true to something else? It really confused me. True makes the feeling, something happened and it is correct.

I would prefer to exit directly, if the input of drink is not in the list. Whatever it shouldn't be true, even undefined is better than true.

[shadowspawn]

If any users of regular expression option read this thread, I am interested in what your code looks like.

[kira1928]

@ozbillwang

How do I write code to identify, if drink's value is not coke|pepsi|izze, exit(-1).

How about this one:

var program = require('commander');

var parseDrink = (function() {
  var regex = /^(coke|pepsi|izze)$/i;
  return function(value) {
    if (regex.test(value)) {
      return value;
    } else {
      console.error(`invalid param ${value}`);
      process.exit(-1);
    }
  };
})();

program
  .version("0.1.0")
  .option("-s --size <size>", "Pizza size", /^(large|medium|small)$/i, "medium")
  .option("-d --drink [drink]", "Drink", parseDrink)
  .parse(process.argv);

console.log(" size: %j", program.size);
console.log(" drink: %j", program.drink);

$ node a.js
size: "medium"
drink: undefined

$ node a.js -d abc
invalid param abc
$ echo $?
255

$ node a.js -d
size: "medium"
drink: true

$ node a.js -d coke
size: "medium"
drink: "coke"

[ozbillwang]

Thanks, @kira1928 👍

I never think to write a function (parseDrink) in the part of program.option . I currently add the test to program.drink

[shadowspawn]

Found another related issue: #708

[shadowspawn]

Closing this in favour of #708

Thank you for your contributions.

[shadowspawn]

Short version: I have downgraded the regular expression support and removed it from the README (!).

See: https://github.com/tj/commander.js/issues/708#issuecomment-496123000