net/textproto: DotWriter inserts extra newline

[gopherbot]

by sam.nguyen@sendgrid.com:

What steps will reproduce the problem?
1. Encode a string with textproto.Writer
2. When it is decoded, it contains an additional newline

Reproduction
http://play.golang.org/p/CBnfXtHpF4

Which compiler are you using (5g, 6g, 8g, gccgo)?
6g

Which operating system are you using?
linux

Which version are you using?  (run 'go version')
1.2rc3

[gopherbot]

Comment 1 by sam.nguyen@sendgrid.com:

Sorry, I think my original diagnosis was incorrect. It looks like textproto.DotWriter
removes a newline if the input ends in a newline. Here is a clearer reproduction:
http://play.golang.org/p/azGP9tlbWb

[gopherbot]

Comment 2 by sam.nguyen@sendgrid.com:

Attached is an updated net/textproto/writer_test.go that covers this case

Attachments:

1. writer_test.go (1022 bytes)

[rsc]

Comment 3:

Labels changed: added go1.3maybe.

[dsymonds]

Comment 4:

Labels changed: added priority-later, packagebug, removed priority-triage.

[rsc]

Comment 5:

Labels changed: added release-none, removed go1.3maybe.

[rsc]

Comment 6:

Labels changed: added repo-main.

[gopherbot]

Comment 7 by walkeraj:

Isn't this behaving as intended?  All bare newlines are converted to \r\n and a '.\r\n'
is added at the end of the buffer when the writer is closed as per spec (see
http://tools.ietf.org/html/rfc5321#section-4.5.2).  The reason this might appear
inconsistent is that you're immediately calling Close(), which triggers the DotWriter to
wrap things up to ensure that the buffer ends with '\r\n.\r\n'
The reason \r\n is added to the end of "foo" is that, when Close() is called, the writer
is in the 'wstateData' state, meaning \r\n is necessary before the .\r\n closing line.
The reason \r\n is added at the end of "foo\n" is that newlines are prefixed with '\r'
when in the 'wstateData' state, which then sets the state to 'wstateBeginLine'.  When in
this state, Close() simply writes out the .\r\n closing line and flushes.  Either way,
this is exactly how you'd expect it to work.

[gopherbot]

Comment 8 by sam.nguyen@sendgrid.com:

Thanks for the explanation. After further reading, yes it looks like you are correct
that this does what is indicated in the documentation:
"DotWriter returns a writer that can be used to write a dot-encoding to w. It takes care
of inserting leading dots when necessary, translating line-ending \n into \r\n, and
adding the final .\r\n line when the DotWriter is closed. The caller should close the
DotWriter before the next call to a method on w."
-- http://golang.org/pkg/net/textproto/#Writer.DotWriter
The specified behavior is not what I expected, but my expectations seem to be off-target.

[bradfitz]

Comment 9:

Status changed to Retracted.