Yeah, the problem is call/return: you have to return something. If you have nothing to return (or not yet → async), things get tricky. What I found really, r

Yeah, the problem is call/return: you have to return something. If you have nothing to return (or not yet → async), things get tricky. What I found really, really nice for error handling is dataflow-style programming, because the main flow only has to deal with the happy path. If you don't have a result, you simply don't send anything to the next filter in the pipeline. And you report errors using a stderr style mechanism, so error handling can be centralised and at a high-level, where you actually know what to do with the errors.