Golang errors: Join docs should mention Is/As

errors.Join docs are terse on how to inspect joined errors. My initial approach, upon reading the following passage

// A non-nil error returned by Join implements the Unwrap() []error method.

was to do something like this:

if joined, ok := err.(interface{ Unwrap() []error }); ok {
  for _, err := range joined.Unwrap() {
     ...
  }
}

Only by reading the docs for errors.Is and errors.As I realized that they can deal with "joined" errors. Let's consider adding a passage to errors.Join such as:

// Joined errors can be inspected through Is and As.

Comment From: gabyhelp

Related Issues

• errors: improve the godoc for Join and Unwrap #59301 (closed)
• errors: add example around unwrapping errors.Join #69586 (closed)
• proposal: rework of errors.Join() #74371 (closed)
• proposal: errors: unwarap joinError to avoid deeply-nested joins #65676 (closed)
• proposal: errors: add Errors function to undo Join #57358 (closed)
• errors: Using `errors.Join` on a `joinError` should expand the existing joined error #60209 (closed)
• errors: errors.Join does not skip nil error interface implementations #70626 (closed)
• errors: unwrap joinError to avoid deeply-nested joins #65360 (closed)

Related Code Changes

• errors: clarify that Join doesn't extend already-joined errors

Related Documentation

• Package errors > func Join 1.20

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