[Haskell-cafe] RE: Darcs and NFS Resolution

[Jason Dagit]

Hi Darrell,

This message definitely also belongs on the darcs-users at darcs.net mailing
list.  You can find information about how to subscribe here:
http://lists.osuosl.org/mailman/listinfo/darcs-users

Please join our list!  I'm adding the list to the CC list in my reply.

On Fri, Sep 11, 2009 at 9:20 AM, Lewis-Sandy, Darrell <darrelll at amgen.com>wrote:

> Thanks to everyone who pointed me in the right direction on this problem, I
> have been able to find a work around that allows me to push to an archive on
> a network file share.
>
> After some digging, I discovered the root of the problem.  Briefly,  Darcs
> uses the standard library System.Directory to perform file manipulations.
>  This library make use of compiler pragmas to conditionally compile either
> the Windows or Linux specific functions based on the host operating system.
>
> This approach assumes that when your operating system is a Linux variant,
> all your mounted volumes will natively support POSIX.  When you have mounted
> CIFS volumes, this will result in errors when calling those library
> functions to create, rename, copy and delete files or folders!   Given the
> flexibility of the Linux operating system, A more versatile implementation
> for System.Directory might be able to detect the file system of each volume
> at runtime and choose the appropriate functions to call.  But I digress...
>
> To workaround the inability to push to a CIFS volume in darcs, I modified
> the workaround.hs module to shell out to the OS's rename function rather
> than using the Haskell library's rename function.  Specifically:
>

Ah clever way to test this.


>
> I added the following code after the #else near line 80:
>
> renameFile :: FilePath -> FilePath -> IO ()
> renameFile old new = do
>     ecode <- System.Cmd.rawSystem "mv" [old,new]
>     case ecode of
>         ExitSuccess -> return ()
>         ExitFailure n -> putStrLn ("renameFile failed with exit code" ++
> show n)
>
> which ensures that when the operating system is not WIN32, that renaming of
> files will be performed by the OS shell.  I then added the System.Cmd module
> to the list of imports by inserting the following code near line 21
>
> import qualified System.Cmd(rawSystem)
>
> after a recompile I could push to a CIFS volume, for example:
>
> sudo darcs push /mnt/cifsvol
>
> this is an obvious hack, and does not address the inability to put to a
> CIFS share (put depends upon copyFile and would need to be hacked to
> shell-out as well).   Archives on the CIFS share have to be created by
> navigating to that folder and initializing.
>

Interesting.


>
> Shelling out is clearly a poor long term solution; a longer term solution
> would ideally introduce into the Haskell System.Directory library the
> ability to apply the correct functions transparently in accordance with the
> file system of the volume.
>

Yes, and in the meantime we can implement something like this in
workaround.hs.

Thanks!
Jason
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