Better error handling for parseAsync()

[HNicolas]

Hello,
When using the new method parseAsync() it seems that it is not possible to override the default error handling behavior :

• calling a command that does not exist, parseAsync() does not throw an error or exit the process, the promise resolve
• calling a command with wrong parameters (missing required parameter) the process exit with code 1

It should be possible to override those default behaviors in order to catch an error like with the sync parse() method.

[shadowspawn]

It should be possible to override those default behaviors in order to catch an error like with the sync parse() method.

parseAysnc() calls .parse(), and you override the default behaviours the same way. I am guessing you have not done that, and would see the same error handling behaviours as you describe if you called .parse() instead?

calling a command that does not exist, parseAsync() does not throw an error or exit the process, the promise resolve

Commander sees a command that does not exist as an argument that you don't happen to handle. (Related collection of issues: #1088)

The current approach is to add a custom event listener and there is an example in README:
https://github.com/tj/commander.js#custom-event-listeners

calling a command with wrong parameters (missing required parameter) the process exit with code 1

See .exitOverride(): https://github.com/tj/commander.js#override-exit-handling

[HNicolas]

I didn't know that it was the correct behavior for when calling a command that does not exist.
But there is still a problem when calling parseAsync() with wrong parameters, I do call .exitOverride() but the process still exit without throwing an error or calling the provided callback if any.
Example of code :

    const program = new Command();
    program.command("test <req>")
      .action(async () => {
        // do some async work
      });
    program.exitOverride()
      .parseAsync(process.argv)
      .catch(error => {
        // not reached on invalid command (missing req)
      });

[shadowspawn]

To get the exitOverride to apply to the subcommand too, define it before adding the command. Then to catch the error I think you need to be in an async context when it is thrown.

const commander = require('commander');
const program = new commander.Command();

program
  .exitOverride()
  .command("test <req>")
  .action(async () => {
    // do some async work
  });

async function main() {
  return program.parseAsync(['node', 'my.js', 'test']); // Oops, req missing
}

main().then(() => {
  console.log('main.then');
})
.catch(error => {
  console.log('main.caught');
  console.log(error);
});

$ node index.js 
error: missing required argument 'req'
main.caught
CommanderError: error: missing required argument 'req'
...

[HNicolas]

It works, thank you for your help.