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Stop writing CLI validation. Parse it right the first time

(hackers.pub)
203 points dahlia | 1 comments | 06 Sep 25 18:20 UTC | HN request time: 0.206s | source
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12_throw_away ◴[07 Sep 25 01:29 UTC] No.45154518[source]▶
I like this advice, and yeah, I always try to make illegal states unrepresentable, possibly even to a fault.

The problem I run into here is - how do you create good error messages when you do this? If the user has passed you input with multiple problems, how do you build a list of everything that's wrong with it if the parser crashes out halfway through?

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1. adinisom ◴[07 Sep 25 05:19 UTC] No.45155610[source]▶
If talking about UI, the flip side is not to harm the user's data. So despite containing errors it needs to representable, even if it can't be passed further along to back-end systems.

For parsing specifically, there's literature on error recovery to try to make progress past the error.