Hacker News Reader

> One of the things Go taught me is that I was not being as careful about my errors as I should be.

I identify with this so much. Especially when dealing with external things (file system, database, network) things can go wrong at nearly every step. And yeah, that means you have to check errors at every step, but it forces you to think about how you want to handle them, and what message you want to propagate when they happen. As a result, my Go code has very few unexpected errors in production.

Hard to overemphasize this. Handling errors is similar to the benefits that writing tests provides - slower upfront, but a more stable product gets shipped.

Handling errors everywhere means problems are already solved before they happen. No 1 am pagerduty alerts because we didn't consider what would happen if a DNS server hung until we timed out and thought just wrapping in a try/catch and crashing was a good idea.

Things can go wrong at every step, which means each collection of fallible steps carries with it a combinatorial explosion of successes and failures. Do 5 fallible statements in sequence and it's 5+4+3+2+1 = 15 mock expectations you need to write. This tedious enumeration exercise is the majority of the time that goes into writing Go programs, for me at least.

Most of the time, you'll return early after an error.

To get into a situation where you'd need to handle n! cases, you'd need to keep running the statements after a failure, and then collate and return all the errors at the end.

Not sure why you'd want to do that. You'd definitely need to go out of your way to do something like this, and probably start asking yourself why you're doing this pretty early on. Plus it would flat out refuse to compile in some cases where there are dependencies between the statements.

It’s + not * in that example.

Ah, okay. In that case it becomes

  {n + 1 \choose n - 1}

What code are you writing that results in this set of possibilities?

I have some code where I use multierrors and collect everything into one big error (I highly recommend this for "validation"-type code, you should generally return all errors not merely the first), but what code are you writing where you're running 5 statements unconditionally but need to handle nearly-arbitrary combinations of them failing, and multierrors aren't what you need?

If you have 5 statements like "if err := doThing(); err != nil { return err }" then you need to simulate the success of all 5, success of the first 4 and failure of the last, success of the first 3 and failure of the 4th, success of the first 2 and failure of the 3rd, etc.

For a total of six cases to deal with. Not 15.

I said 15 mock expectations, not cases.

If all five of those things also need to be independently mocked, you're mocking too much and your mocks suck.

If they're not mocked it's an integration test. Integration tests are welcome as a supplement to unit tests, but unit tests are table stakes.

An automated test suite is table stables. If you can achieve correct, maintainable code better with functional or integration tests than unit tests, you should.

There is no hard technical line between "unit test" and "integration tests", it's a semantic question of how you define your units. Even if do you take a tiny, restrictive definition of your units, you could still use a fake or stub instead of a mock.

https://martinfowler.com/articles/mocksArentStubs.html

To get very specific for Go, we use testify suites, tend to set up fully functional stubs in `SetUp`, and then test cases either use them to verify happy paths, or `s.BreakStep1()` in one test, `s.BreakStep2()` in the next, etc. So in this case we would write a total of five extra lines for the five possible ways to break.

I think that is a fair opinion and my life at work would be better if others shared that opinion. Go however does officially stake out the opposite position: coverage only "counts" if the test is in the same package as the unit under test.

Go’s error handling is a strange this to praise considering it is entirely possible to ignore it without warning and the way to check error kinds was bolted on through type assertions when errors are supposed to be values in Go. Error kinds are important especially in network programming when the error can be dozens of different things. Compare this to something like Rust or Haskell which force you to handle errors and their variants.

Pretty much every form of Go tooling warns you when you ignore an error. If you only choose to run "go build", yes you can ignore it, but a simple "go vet" call and it'll be plain as day.

    a, err := foo() // oops, unhandled error
    err = bar()
    if err != nil { ... }

or

    fmt.Println("...") // oops, unhandled error

or more insidiously

    err1 := foo()
    if err1 != nil { ... }
    err2 := bar()
    if err2 != nil { return err1 } // oops

In the first and the last case, it seems obvious to me where the error is. An obvious code smell caught in review. The second error, yeah, but lots of languages don't enforce error handling around printing to stdout, and even though Rust does in theory, in practice everyone just unwraps it and moves on with their day.

> but lots of languages don't enforce error handling around printing to stdout

They do, they throw exceptions.

> In the first and the last case, it seems obvious to me where the error is

The last case is especially insidious. I've seen it in production several times now. Very easy to miss. Particularly when refactoring/copy pasting code (which you have to do a lot of in golang).

Certain things need to be available out of the box.

The whole point of a programming language is to make the programmers life easier.

By now decades of exposure to programming languages have made try/catch the standard way of working with errors. Forcing the programmer to guess issues, when the compiler/runtime could be doing it- IMO is just plain waste of human labor. And for even medium to large applications is a pointless exercise.

Once again Rust does not force you to handle errors, you can ignore errors in Rust and it will compile. I can't say for Haskell but I doubt there is a language that forces you to handle error.

let _ = openFile()

Error ignored, it does compile, it will probably ends badly.

As for network error: https://pkg.go.dev/net#OpError

This is exactly my experience. Being forced to handle so many more errors showed me how much error handling I was inadvertently eliding in other languages!

I think this is for sure the first time I have ever heard someone say that Haskell makes it too easy to handle error cases.

To be more precise, it is the language that makes error-as-values so easy that it actually strays over into "as easy to forget about errors as exception-based handling".

You can successfully build huge chains of code that are just blindly passing errors up without adding any context about where they happened or anything in a way that even Rust can't compete with.

Haskell mitigates this issue by also having one of the more clever ways of dealing with errors, if you start getting into monad transformers or some of the advanced stuff, so it's not all bad. But it definitely can make it so easy to "handle" errors that you just forget about them.

I've used Scala in production codebases and it was common to just "let the EitherTs handle the exceptions". What ended up usually happening was swallowed exceptions that nobody bothered to handle and log because it was much less idiomatic Scala/FP to actually log what happened underneath than it was to return the first error that happened by short circuiting the EitherTs in for/yields (Maybe and do notation, for Haskellers). So we'd get 5xxes and log lines like "row not found" and have absolutely no idea why.

I see a lot of the same issues in Rust code today FWIW. People just keep bubbling up errors and at the toplevel say "fuck it" and dump them, without _actually_ building a reasonable error chain to offer the programmer a story behind how the error happened. The fact is, error handling in any language is tedious. Whether you do it with a sum type, a product type, or Go's error values, either way there's going to be lots of verbosity and boilerplate.