v2 DebugWriter breaks LOGIN or any imap command

[resolutecake]

• if the DebugWriter option is used as an argument to github.com/emersion/go-imap/v2/imapclient.New,
• any invocation of github.com/emersion/go-imap/v2/imapclient.Client.Login will fail

this is because:

• github.com/emersion/go-imap/v2/imaplicent.Options.wrapReadwriter
• wraps net.Conn using io.MultiWriter
• then that writer is wrapped by *bufio.Writer

Now Flush will always fail meaning the first command is sent out and then "short write" error occurs bufio.Writer.Flush

Multiple buffered wrapping does not work in Go

version: 0196200 12/26/2023

[resolutecake]

Actually, the root cause was that my debug writer did not update sent bytes, returns n int This causes the short write. If the debug writer fails, this error is indistinguishable from a communications failure

[emersion]

This is expected behavior. If the debug writer fails, it's normal for go-imap to return an error.