os: Rename on Plan 9 handles newname incorrectly

[gopherbot]

by mischief@offblast.org:

os.Rename on Plan 9 simply does a Wstat, which has some limitations that make its use
behave different than normal use cases.

http://plan9.bell-labs.com/magic/man2html/5/stat

you cannot move a file between directories with os.Rename on plan 9, since it only does
Wstat. to do this you must do a create/copy/remove.

much code appears to expect to be able to pass a full path component in the newname
argument. this fails because you cannot pass a slash to Wstat.

with both of these, code must have a special case for doing renaming operations on plan
9.

os.Rename should probably try to closer match the code in
http://plan9.bell-labs.com/sources/plan9/sys/src/cmd/mv.c

[rsc]

Comment 1:

The handling of newname is definitely wrong. The code must check that the two paths have
the same leading directory and then pass only the final element.
However, the first half of the suggestion is wrong too: os.Rename is allowed to fail for
different directories and on Plan 9 it should. It is a mistake to do the Copy behind the
user's back. os.Rename can fail on Unix too, if the directories are on different file
systems.
Since Plan 9 is not a supported system, this will have to wait until Go 1.3.

Labels changed: added priority-later, go1.3, removed priority-triage.

Status changed to Accepted.

[4ad]

Comment 2:

I agree with rsc, people use os.Rename for its atomic behavior. We cannot do this in
Plan 9 for as many use cases as for Unix, but we must not lie to the consumer that we
can.

[rsc]

Comment 3:

Labels changed: added release-go1.3.

[rsc]

Comment 4:

Labels changed: removed go1.3.

[rsc]

Comment 5:

Labels changed: added repo-main.

[rsc]

Comment 7:

Plan 9 guys, please fix for Go 1.3 (or maybe it already is?)

[0intro]

Comment 8:

I missed this issue report. I believe this problem has been fixed in CL 44080046 (and
more recently in CL 65270044).

[ianlancetaylor]

Comment 9:

Thanks.  Closing as fixed, please reopen if it turns out not to be.

Status changed to Fixed.