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Comment by thinkharderdev | Hacker News Reader

Very true, but I do think there is an issue in the margin about how easy it is to ignore errors. For example, in Java you might have something like

``` void checkPermissions() throws AuthException ```

so you have to actively ignore errors by catching the exception. Likewise in Rust you can do

``` fn check_permissions() -> Result<(),AuthError> ```

In that case you can just use the `?` operator to short-circuit (and clippy will warn you if your forget to do that).

In other words, while language design can't fully prevent you from ignoring precondition checks, it can make it harder to forget or even force you to actively ignore precondition failures

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But isn't the idiomatic Go solution something like this?

    func checkPermissions(success func())

Like anything, you can still screw it up if you try hard enough, but it should nudge most in the right direction. The talk of error handling seems like a distraction or a case of someone confusingly trying to write code in another language using Go syntax.

Obviously you are not forced to think of the user when designing an API, but you don't have to be mindful of the user in any language. Not even Haskell can save a developer who doesn't care, as noted in an earlier comment.

Go linters do a pretty good job of spotting where error return values have been ignored, so I'd suggest that the kind of bug the OP is referring to is pretty unlikely to happen in a Go project that's properly configured.

Sure - my question is "why do you need to set up the third party linters when they're so critical to the correctness of your program" really. It's the general "yeah we'll give you these footguns which are the first thing every developer will learn about during their first incident; good luck, and I hope you know you need to do things this way!" attitude I object to.

> my question is "why do you need to set up the third party linters when they're so critical to the correctness of your program" really.

No doubt the same reason it is also critical in Haskell (see comment about isLoggedIn function): Developers not knowing what they are doing.

If you work within the idioms and generally accepted programming practices this isn't a problem. It only becomes a problem when you get a developer who wants to "go their own way" without understanding why the norms exist. The linter is a crutch to support their "bad habits".

There’s no simple solution when it comes to ignoring errors. Some errors should be ignored and some shouldn’t. So your only lines of defense are linting heuristics and tests.

I would agree that languages which handle errors via exceptions have an advantage here, as they make not ignoring errors the default behavior. But even then, it’s obviously still possible to indicate error conditions of various kinds via return values, in which case they can still be ignored thoughtlessly. (And you also have all the bugs caused by unhandled exceptions to deal with.)

> Some errors should be ignored and some shouldn’t.

Assuming the function author followed Go conventions, you never need to consider the error for the sake of using the function. Granted, there are some bad developers out there who will do something strange that will come to bite you, but that is not limited to errors (or any particular language).

You may still need the error for your own application requirements, but application requirements are pretty hard to forget. At very least, you are going to notice that your application is missing a whole entire feature as soon as you start using it.

Any function that returns an error obliges its callers to check that returned error before attempting to use any other returned value.

This is Go 101 type stuff.

While you might be forced to if faced with a developer who doesn't know what the hell they are doing, that is not the convention.

Consider the case of (T, error). T should always be useable, regardless of error. At very least, if there is nothing more relevant to provide, the function should return the zero value for T. And we know that in Go the zero value is to be made useful. Go Proverb #5.

In practice, this often means something like (*Type, error), where the zero value for *Type (nil) is returned on failure. In which case the caller can check `if t == nil`. No need to consider the error at all. It is there if your requirements dictate a need for the error (e.g. reporting the failure), but for using the result it is entirely unnecessary.

If you leave the caller in a state where T can be invalid, you screwed up horribly or are purposefully being an asshole. Don't do that. That is Go 101 type stuff.

> Consider the case of (T, error). T should always be useable, regardless of error.

Go convention dictates that T is only valid (usable) when error is nil. Equivalently, if error is non-nil, then T is invalid (unusable). In either case, the caller is obliged to verify error is non-nil before trying to access T.

You're still only halfway there, as we discussed earlier.

Go calling convention is that you have to assume T is invalid, unless proven otherwise, because we know there are developers who have no business being developers that will screw you over if not careful. The Go style guide promotes documenting in a function comment that your function does return a valid T so that users don't have to guess about whether or not you are competent.

But the convention on the function authoring side is to always ensure T is valid. Just because others shouldn't be writing code does not mean you need to be among them.

As Go promotes limiting use of third-party packages by convention, as a rule most of the functions you call are going to be your own. So most of the time you can be sure that T is valid, regardless of error state. Yes, sometimes you are forced to rely on the error, as we discussed already in earlier comments. Such is life.

> the convention on the function authoring side is to always ensure T is valid.

I'm not sure where you got this idea from. It's not (in the general case) true. But do as you like, of course.

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