all: document that error.Unwrap was added in 1.13

[rillig]

What version of Go are you using?

1.12 and 1.13

What did you do?

To classify network errors, I used the Unwrap method:

func classifyNetworkError(err error) string {
	cause := err
	for {
		type nested interface{ Unwrap() error }
		unwrap, ok := cause.(nested)
		if !ok {
			break
		}
		cause = unwrap.Unwrap()
	}
	return cause.Error()
}

The Unwrap method comes handy, I just wondered why there is no predefined interface like NestedError for that method.

I got strange differences between Go 1.12 and Go 1.13, which I couldn't explain. In Go 1.12 the errors were not unwrapped at all.

What did you expect to see?

The Unwrap in all error types are clearly documented as "added in 1.13".

What did you see instead?

Nothing.

References

• net: Document that DNSError.IsNotFound has been added in 1.13 #36767
• commit 170b8b4

[smasher164]

I looked through the Unwrap methods on exported types, listed here (https://golang.org/search?q=Unwrap), and notice that they all list "1.13" on godoc. What additional documentation do you have in mind here?

[rillig]

Oops, I must have missed that information. Or, which is more likely, I trusted my IDE to show me all relevant information, which it didn't.

When I looked at the implementation of the various Unwrap methods, I didn't see any version being mentioned. Therefore I thought it was missing. In addition, even after I found the commit that added the Unwrap methods, that commit did not add the entries to api/go1.13.txt, which I would have expected.

With all this additional information, the golang project is fine. I'll tell JetBrains to improve their IDE by marking the API level of each definition. Thanks for the help.