Exceptions and error() are unusable in onComplete handler

[bentsherman]

Slack thread: https://nextflow.slack.com/archives/C02T98A23U7/p1696364290193959

Exceptions can't be thrown from the workflow onComplete handler because they are immediately caught by Nextflow and logged as an error:

nextflow/modules/nextflow/src/main/groovy/nextflow/script/WorkflowMetadata.groovy

Lines 391 to 398 in dfb5bf0

	onCompleteActions.each { Closure action ->
	try {
	action.call()
	}
	catch (Exception e) {
	log.error("Failed to invoke `workflow.onComplete` event handler", e)
	}
	}

This also affects the error() function, which throws a WorkflowScriptErrorException under the hood. Throwing an exception is a useful way to fail the entire run if some final validation does not succeed.

On the other hand, if some unexpected exception is thrown, the current logic prevents the entire run from failing, which can be nice.

A good solution might be to re-throw WorkflowScriptErrorException but catch and log all others.

[pditommaso]

A good solution might be to re-throw WorkflowScriptErrorException but catch and log all others.

Sounds good