Global error handler for ace commands

[JustasStarred]

Handling errors in a HTTP context is easy with a global exception handler, I'm looking to do the same with Ace commands. Ultimately, my goal is to get all errors from failed node ace calls into Sentry. I've see this discussion and am already using that package, however it only handles HTTP context errors.

I looked into bin/console.ts, which already comes with an example to hook into the lifecycle. I thought it would be as easy as initialising Sentry in the initiation hook and then calling Sentry.captureException in the catch().

Given a test command:

export default class TestError extends BaseCommand {
  static commandName = 'test-error'

  async run() {
    throw new Error('A sample error')
  }
}

The catch() in bin/console.ts does not get called. Upon further investigation it's because the ace Kernel handles the error by calling errorHandler.render. There is no way to override this error handler, nor does the default ExceptionHandler offer a way to hook into it.

I did however notice that the ace Kernel keeps a reference to the "main command" which is an instance of BaseCommand that itself keeps a reference to error thrown while executing. I then modified the bin/console.ts to:

app.terminating(async (a) => {
  console.debug('terminating')
  const ace = await app.container.make('ace')
  const cmd = ace.getMainCommand()
  if (cmd && cmd.error) {
    console.error(`${cmd?.commandName} command terminated with error:`, cmd.error)
    // TODO report to Sentry
  }
})

While this works, it has to rely on the getMainCommand which I do not believe is documented anywhere. It does not work for built-in commands like migration:run since they have their own error handling. Given that it will only work for custom-commands, it's easier to simply wrap BaseCommand with error handling and making all commands inherit from it.

Additionally, the approach gets more complicated because by default ace commands do not boot the application.

In a perfect scenario, I would argue that the ace kernel should come with it's own equivalent of exceptions/handler.ts, or atleast the ability to set one. Even if that won't address commands like migration:run which do not throw on error.