[tahoe-lafs-trac-stream] [Tahoe-LAFS] #2235: Error from 'tahoe cp' on Windows, due to a long path (IOError: Errno2 - no such file or dir.)

[Tahoe-LAFS]

#2235: Error from 'tahoe cp' on Windows, due to a long path (IOError: Errno2 - no
such file or dir.)
--------------------------------+------------------------------------------
     Reporter:  CyberAxe        |      Owner:  Zancas
         Type:  defect          |     Status:  new
     Priority:  normal          |  Milestone:  undecided
    Component:  code-frontend-  |    Version:  1.10.0
  cli                           |   Keywords:  tahoe-cp error windows win32
   Resolution:                  |
Launchpad Bug:                  |
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Comment (by daira):

 Because prepending `\\?\` is not correct for a UNC path (
 [http://msdn.microsoft.com/en-us/library/aa365247%28VS.85%29.aspx#maxpath]
 ):

 > The "\\?\" prefix can also be used with paths constructed according to
 the universal naming convention (UNC). To specify such a path using UNC,
 use the "\\?\UNC\" prefix. For example, "\\?\UNC\server\share", where
 "server" is the name of the computer and "share" is the name of the shared
 folder. These prefixes are not used as part of the path itself. They
 indicate that the path should be passed to the system with minimal
 modification, which means that you cannot use forward slashes to represent
 path separators, or a period to represent the current directory, or double
 dots to represent the parent directory. Because you cannot use the "\\?\"
 prefix with a relative path, relative paths are always limited to a total
 of MAX_PATH characters.

 It is also not correct for a path that already starts with `\\?\` (or,
 more obscurely, `\\.\`).

 I could have written code like this to cover all cases:
 {{{
 if sys.platform == "win32":
     if path.startswith(u"\\\\?\\") or path.startswith(u"\\\\.\\"):
         pass
     elif path.startswith(u"\\\\"):
         path = u"\\\\?\\UNC\\" + path[2: ]
     else:
         path = u"\\\\?\\" + path
 }}}
 but I don't actually care about long UNC paths; I just wanted to avoid
 doing something obviously incorrect for them.

--
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2235#comment:17>
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