On Mon, 23 Mar 2020 at 11:22, Axel Wagner <axel.wagner...@googlemail.com> wrote:
> • A function takes an io.Reader to parse the stream into some data structure > (think a json-parser). It obviously uses no other input or abstraction or > state. It makes sense to wrap the error - this allows you to provide > structured extra information (like offsets) to the user of the library and > better error messages, while maintaining your users ability to switch on what > actually went wrong. That's a good point, and I suppose it generalises. Whenever you receive an interace from client code, then you have no compiler-enforced way to predict which errors you'll get from calls to that interface; but your client might. Therefore you should either pass the error up directly or else user wrapping. (Microsoft has/had the problem that many Windows APIs let clients implement abstract classes for OS middleware to call. The MSDN page for each method would list which error codes were allowed for the method, but they had no way to enforce this, so the middleware had to try and handle all possible errors). > That latter part, BTW, is IMO a blessing and a curse. It's a blessing, > because it can reduce coupling from details in the wrapping case. ... I think this is the classic dynamic vs. static typing trade-off. Go has always been a mostly static language but happy to sprinkle in dynamic typing stategically through interfaces and reflection. By standardising on the `error` interface, Go chose error handling as one of those dynamic sprinkles. > Sorry if this message is a bit chaotic and stream-of-consciousnes-y :) I > haven't quite figured out how to talk about all of this yet :) > I guess the tl;dr is, that I tend to agree - don't just use %w without > thinking. Make a deliberate choice if you want to commit to this API detail. > And as usually in API design: If in doubt, prefer to start out with less > commitment, flexibility and surface. So to turn this discussion into something actionable: should this advice be added into the documentation? And if so, where (in package fmt or errors)? Lots of programers will assume that because %w is new, then it must be the Go team's recommended "best practice". I think I was unconciously thinking that until I read the blog post. -- Adrian Ratnapala -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAN%2BHj7gvJru-ZoLUcdcCNde3iJgK5j6aoCbipksCRMYSMznjfw%40mail.gmail.com.
