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Comment by gwd | Hacker News Reader

The frustrating thing is that the error in question already is a sentinel error -- Grafana (the top-level culprit in the linked search) should be using `errors.As(&http.MaxBytesError{})` rather than doing a string compare.

The whole point of Hyrum's Law is that it doesn't matter how well you design your API: no matter what, people will depend on its behavior rather than its contract.

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But it looks like that until 3 years ago, this string comparison was the only way to do it. https://github.com/golang/go/pull/49359/files

Good catch. So in a sense this isn't really Hyrum's Law (which would be more appropriate to things like the Sim City / Windows 3.x UAF bug described in a sibling comment); it's more like, if people need to do something, and you don't give people an explicit way to do it, they'll find an implicit way, and then you're stuck supporting whatever that happened to be.

There was a well-known trick in MacOS development in the 90s. You couldn't always avoid relying on undocumented behavior. The docs were incomplete and occasionally vague.

What you could do was try to rely on the same undocumented behavior as everyone else. This way, if Apple broke you, they'd break half their ecosystem at the same time.

Or they could have fixed the error (adding the type) instead of matching the string.

Early Go lacked lots of features such as errors.As. It was and still is sometimes idiomatic to generate Go because it is so featureless and writing it is often a chore. So it is very much about how well you design your API.

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