net/http: export `errCannotRewind`

[dillonstreator]

go/src/net/http/transport.go

Line 628 in dee3efd

var errCannotRewind = errors.New("net/http: cannot rewind body after connection loss")

I'm having to resort to string matching to identify this error which is not ideal

strings.Contains(err.Error(), "net/http: cannot rewind body after connection loss")

I'd love to just be able to use errors.Is

errors.Is(err, http.ErrCannotRewind)

[gopherbot]

Change https://go.dev/cl/420574 mentions this issue: net/http: export errCannotRewind``

[neild]

What is the use case for distinguishing this error?

[dillonstreator]

What is the use case for distinguishing this error?

controlling a log level

[neild]

I don't think this is an error we want to expose. We generally only add distinguishable errors for conditions where code can make a meaningful choice depending on the type of error; this doesn't seem to be such a case.

If we did want to expose this condition, simply exporting errCannotRewind would not be sufficient, since it's only used by the HTTP/1 implementation.