[sagichmal]

Of course you can. Sad path first means, after you write your data types and interface signatures, writing the first stub implementations as

    func (t *Thing) Process(id int) (string, error) {
        return "", fmt.Errorf("not implemented")
    }

and then filling them in gradually like

    func (t *Thing) Process(id int) (string, error) {
        dat, err := t.store.Read(id)
        if err != nil {
            return "", fmt.Errorf("error reading ID: %w", err)
        }
        
        cert, err := dat.ExtractCertificate()
        if err != nil {
            return "", fmt.Errorf("error extracting certificate: %w", err)
        }
        
        return cert.Name(), nil
    }

and explicitly not

    func (t *Thing) Process(id int) (string, error) {
        dat, _ := t.store.Read(id)          // TODO: error handling
        cert, _ := dat.ExtractCertificate() // TODO: error handling
        return cert.Name(), nil
    }

Writing code this way, explicit error handling upfront, is fundamental to reliability (for a large class of applications).

[tsimionescu]

Sure, but in a better language, the second version already does the exact same thing as the first one. Your `return fmt.Errorf` is not exception handling, it is simply manual exception bubbling. It is boilerplate that you can forget to add, and that makes it harder to understand what the code is supposed to do. Maybe for the first error you are adding some context that the Read function didn't have, but for the second, the error handling code is doing absolutely nothing that an automatic exception stack trace didn't do.

Even worse, with this style of programming, someone up the stack who would actually want to handle these errors has no mechanism to do, since you're returning the same type from both error cases. If they wanted to handle the certificate error but not the read error, they would have to parse the error message string, which is brittle. But if you did want to add appropriate context, your function would bloat even more. Not to mention that the standard library doesn't really help, since it generally doesn't define any specific error types to set up some patterns for this. Even in your example, from the start you assumed that your function can either succeed or fail in a generic way, you didn't think that the signature may want to encode multiple different error types, which is what GP was talking about when saying you can't usually think about the sad case before the happy case. Sure, if the extent to which you want to define sad case first is 'sad case can happen', you can.

Go's error handling strategy is its weakest aspect, and it is annoying to hear advocates pretend that Go is doing it right, when 90% of Go code is doing the same thing as 90% of exception-based code, just manually and with less helpful context for either logging or for the 10% of code which actually wants to handle errors.

[sagichmal]

> Sure, but in a better language, the second version already does the exact same thing as the first one. Your `return fmt.Errorf` is not exception handling, it is simply manual exception bubbling.

You look at what I'm doing as a more tedious and error-prone version of exception bubbling, but that misses the forest for the trees. The whole point of doing it this way is to lift errors out of the shadows of the exception control flow path, and put them front-and-center in the actual logic of the application. Programming (in many domains) is error handling, the error handling is at least and arguably more important than the business logic.

I don't want exceptions. I do want this (or something like it).

> Even worse, with this style of programming, someone up the stack who would actually want to handle these errors has no mechanism to do, since you're returning the same type from both error cases.

As the author of this module, I get to decide what my callers are able to see. What I've written is (IMO) the most straightforward and best general-purpose example, where callers can still test for the wrapped errors if they need to. If it were important for callers to distinguish between Read and Certificate errors, I would use sentinel errors e.g. var ErrCert (if the details weren't important) or custom error types e.g. type CertificateError struct (if they were).

Adding this stuff isn't bloat. Again, it's just as important as the business code itself.

> Go's error handling strategy is its weakest aspect, and it is annoying to hear advocates pretend that Go is doing it right

In industry, considering languages an organization can conceivably hire for, and considering the general level of industry programmers -- programs written in Go are consistently in the top tier for reliability, i.e. fewest bugs in logic, and fewest crashes. Certainly more reliable than languages with similar productivity like Python, Ruby, Node, etc.

There are plenty of flaws in Go's approach to error handling -- I would love to have Option or Result types, for example -- but I think, judging by outcomes, it's pretty clear that Go is definitely doing something right.

[apta]

> programs written in Go are consistently in the top tier for reliability.

Citation needed. It may simply be that those code bases are doing relatively trivial work compared to large programs in other languages, where bugs are more likely to happen simply due to code size. Even in this thread another poster wrote:

> I've accidentally introduced way more bugs through Go style error handling than through Python style error handling.

I've seen production golang code where errors were being silently overwritten. Much, much worse than anything in Java or C# where exceptions are explicitly swallowed.

[tsimionescu]

I'm not missing the forrest for the trees, I know your argument and reject it.

Again, if you had showed an example where something is actually being done with the errors, I would have agreed with you 100%. But when all that is being done is bubbling the errors, having this be done manually by the programmer (and read every time by the code reviewer) is both inefficient and error-prone. Not to mention that one of the first 'skills' I developed as a Go programmer was to ignore any block starting with 'if err != nil', since it appears so, so much in the code. It's not uncommon to have one function contain 10 different 'if err != nil { return nil, fmt.Errorf("Error doing X %v", err)}' for trivial logic (make 10 calls to some external service, abort if anything fails).

I don't have a problem with encoding errors in the function return type. But, coupled with Go's inability to abstract any kind of control flow, this error 'handling' strategy is almost as bad as C's. Other languages that don't offer exceptions avoid this problem with higher level control mechanisms, such as monads or macros.

Even worse, the Go designers recommend some horrible patterns [0], like Scan() not returning an error, but putting the scanner in an error state that all other Scanner functions respect, and having client code explicitly check for the Error() property of the scanner object at the end - preventing any generic tool from helping check whether you correctly handle errors in your code, and introducing an entirely different pattern.

And I don't know the source of your claim about Go's reliability, but all of the studies I have read comparing programming languages have found no or very little effect of the choice of language on overall number of bugs. One recent study [1] which included Go did have it as one of the more reliable languages (but behind Ruby, Perl or Clojure), but with a very minor overall effect, that may be explained by many factors other than error handling (they did not compare languages by this aspect).

Edit: And one minor point, but I did miss the %w in your example code, which does indeed make it possible for code consuming your errors to differentiate them. In my defense, this is a feature of the very newest version of Go only; and having the difference between a 'testable' error and a not testable one be %w vs %v in a format string seems a design decision particularly hostile to code review.

[0] https://blog.golang.org/errors-are-values

[1] https://www.i-programmer.info/news/98-languages/11184-which-...

[sagichmal]

> I know your argument and reject it.

And I yours, so it seems we're just at an impasse of opinion. That's fine. We can continue being productive in our own ways, and history will judge the superior approach, in whole or part.

[alessandrasa]

`If they wanted to handle the certificate error but not the read error, they would have to parse the error message string, which is brittle.` Aaargh that is my main pain with Go error handling. I try to have an open heart with all the verbose way of living, but this "select by error type" when I want to treat errors really feels awkward