TIL: First problem with commander...

In yesterday’s blog I talked about how I found out about the node package commander for handling command line properties. Well, when I went to start using it in a project today, I ran into the same issue that evidently everyone runs into…

For what seems like at least the last 4 years now, there have been multiple open issues regarding the fact that commander will not make an argument mandatory if that argument has a mandatory field.

Before we get to the why and how, let’s look at a simple example of how commander works:

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const commander = requires('commander');

commander
 .version('0.0.1')
 .option('-n, --number <num>', 'Number of things')
 .parse(process.argv);

console.log(commander.number);

Above I define that I will have one option when using the app, number and that it will be accessible either by using -r or --r. By using the < > brackets, I note that a parameter is required when using that flag. Finally, I give a definition of the argument when running -h for help.

However, there’s no way to actually mark that the -n flag is required when using this means of defining your application options. Even though I’ve denoted that a parameter is required, that only will be enforced when actually setting the -n flag in the command line. Running without the -n will bypass any and all checks.

So, the simple solution I found to this was to simply do the following:

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const commander = requires('commander');

commander
 .version('0.0.1')
 .option('-n, --number <num>', 'Number of things')
 .parse(process.argv);

if (!commander.number) {
   console.log('-n is mandatory. See help for more details on how to use the flags');
   process.exit(1);
}

console.log(commander.number);

This way, we check to see if the required parameter has been set up front. If it hasn’t, we abort right away. If it has, we continue on.

💚