Comment by quotemstr | Hacker News Reader

Comment by quotemstr | Hacker News Reader

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Hard disagree. Exceptions are actually good. They make code clear and errors hard to ignore. I've written a ton of code over decades in both exceptional and explicit-error languages and I'll take the former every day. There's no function color problem. No syntactic pollution of logic with repetitive error propagation tokens.

Also, exception systems usually come with built in stack trace support, "this error caused by this other error" support, debugger integration ("break the first time something goes wrong"), and tons of other useful features.

(Common Lisp conditions are even better, but you can't have everything.)

You can't just wave the word "goto" around as if it were self-evident that nonlocal flow control is bad. It isn't.

> And nearly always, after an exception is “handled”, the application is actually in an unknown state and cannot be reasoned about.

That's not been my experience at all. Writing exception safe code is a matter of using your language's TWR/disposable/RAII/etc. facility. A programmer who can't get this right is going to bungle explicit error handling too.

Oh, and sum types? Have you read any real world Rust code? Junior developers just add unwrap() until things compile. The result is not only syntactic clutter, but also a program that just panics, which is throwing an exception, the first time something goes wrong.

Many junior developers struggle with error handling in general. They'll ignore error codes. They'll unwrap sum types. They might... well, they'll propagate exceptions non-fat ally, because that's the syntactic default, and that's usually the right thing. We have to design languages with misuse in mind.

> Have you read any real world Rust code? Junior developers just add unwrap() until things compile.

If you really don't like unwrap[1], you can enable a linter warning that will let you know about its uses to flag it during code review. You know exactly where they are and when they happen. Exceptions are hidden control flow, so you rely on documentation to know when a function throws.

> Writing exception safe code is a matter of using your language's TWR/disposable/RAII/etc. facility. A programmer who can't get this right is going to bungle explicit error handling too.

Rust has RAII, so you don't have to worry about clean-up when returning errors. This is a Go problem, not Rust.

[1] https://blog.burntsushi.net/unwrap/

Bah, no, I hated that you had to wrap basically every code block in a try/catch in Java, because the underlying lib could change and suddenly throw a Runtime-Exception.

At the same time Checked Exceptions were a nightmare as well, because suddenly they were part of the contract, even though maybe wrong later.

> the underlying lib could change and suddenly throw a Runtime-Exception.

And what would you do in that case? Since this is a future change your existing code presumably wouldn't know what else to do but throw its own exception, so why not just let that one propagate?

Always depends on which level it happens

Checked exceptions are more trouble than they're worth. That doesn't make exceptions in general bad.

Not having checked exceptions is a huge problem, because then you never know when something might throw and what it might through, and in the .NET world the documentation on that is pretty awful and absolutely incomplete.

But then over in Java world, your checked exception paradise (which it of course isn't because the syntax and toolkit for managing the things is so clunky) is easily broken by the number of unchecked exceptions which could be thrown from anything at any time and break your code in unexpected and exciting ways, so not only do you have to deal with that system you also don't get any assurance that it's even worth doing.

But this doesn't actually mean checked exceptions are a bad idea, it means that Java didn't implement them very well (largely because it also has unchecked exceptions, and NullPointerException is unchecked because otherwise the burden of handling it would be hideous, but that comes down to reference types being nullable by default, which is a whole other barrel of pain they didn't have to do, and oh look, Go did the same thing wooo).

> in the .NET world the documentation on that is pretty awful and absolutely incomplete.

Depends on the area you look at. Language documentation is pretty good and so is documentation for the standard library itself. Documentation for the frameworks can be hit or miss. EF Core is pretty well documented and it’s easy to find what to look for usually. GUI frameworks are more of a learning curve however.

FWIW many in Java community consider checked exceptions to be a mistake. While I don’t find writing code that has many failure modes particularly fun with exception handling - Rust perfected the solution to this (and the Go way is visually abrasive, no thanks), I don’t think it’s particularly egregious either - Try pattern is pretty popular and idiomatic to use or implement, and business code often uses its own Result abstractions - switch expressions are pretty good at handling these. Personally, I’d write such code in F# instead which is a recent discovery I can’t believe so few know how good it is.

What does make exceptions bad in my opinion (and shared by Go developers?) is a few things:

1. Exceptions are expensive (at least in Java / C#), as they generate a stack trace every time. Which is fine for actually exceptional situations, the equivalent of `panic()` in Go, but:

2. Exceptions are thrown for situations that are not exceptional, e.g. files that don't exist, database rows that don't exist, etc. Those are simple business logic cases. The workaround is defensive coding, check if the file exists first, check if the row exists? that kind of thing.

3. The inconsistency between checked and unchecked exceptions.

4. Distance - but this is developer / implementation specific - between calling a function that can throw an error and handling it.

But #2 is the big one I think. Go's error handling is one solution, but if it's about correct code, then more functional languages that use the Either pattern or whatever it's called formally are even better. Go's approach is the more / most pragmatic of the options.

> e.g. files that don't exist, database rows that don't exist, etc. [...] The workaround is defensive coding, check if the file exists first, check if the row exists?

Ugh NO. Please don't. You should never "check if the file exists first". It can stop existing between your check and your later attempt at opening the file (the same with database rows). That can even lead to security issues. The name for that kind of programming mistake, as a vulnerability class, is TOCTOU (time-of-check to time-of-use).

The correct way is always to try to do the operation in a single step, and handle the "does not exist" error return, be it a traditional error return (negative result with errno as ENOENT), a sum type (either the result or an error), or an exception.

Totally agreed, but as the previous poster wrote:

an exception is meant for EXCEPTIONAL behavior.

So it may be that the file access throws an exception but generally, I wouldn't agree.

As said, I don't like the wrapping of about everything with try/catch

Sure, you can only do it way up the stack, but that's not enough quite often.

If you can only do it all the way up, I find it ergonomic.

Maybe I should experiment more with catch unwind in Rust.

> Oh, and sum types? Have you read any real world Rust code? Junior developers just add unwrap() until things compile.

Junior developers will write suboptimal code in any language. So I'm not sure what your point is.

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