On windows command "p: view this patch in full with pager" fails. "darcs.exe:
less: runProcess: does not exist (No such file or directory)"

Command that is "less" alternative on windows is called "more".

You can define the PAGER environment variable to be more, and things should work
fine.

Thanks for the hint, but I hope this is not user support tracker and some steps
will be taken to avoid this situation in future versions. =)

On Mon, Mar 31, 2008 at 04:14:35PM -0000, techtonik wrote:
> Thanks for the hint, but I hope this is not user support tracker and some steps
> will be taken to avoid this situation in future versions. =)

Me too.

David

I'm marking this as a bug.

The view_file function, which is used by darcs to pipe patches through a pager
(Darcs.PrintPatch.printPatchPager), looks like this:

view_file :: String -> IO ExitCode
view_file f = do
  viewer <- get_viewer
  exec_interactive viewer f
             `ortryrunning` exec_interactive "less" f
             `ortryrunning` exec_interactive "more" f

which makes me think that it should at try "more" if "less" is not found.  Why
is this not actually happening?

From issue784 , David's proposed solution is to default to printing-on-screen if
no pager is found.  This definitely sounds like a sensible alternative, so we
should implement that.

On the other hand, it would also be really good if we figured out why defaulting
to 'more' does not actually work...

There's more to that.

I use restricted account for all developing for security reasons. Therefore, I
cannot create a file at C:\

C:\>darcs --help
darcs version 2.0.0 (2.0.0 (+ 19 patches))
darcs.exe: openFd: permission denied (Permission denied)

darcs attempts to create a temporary file for paging into this directory. The
same probably happens with repository in CD-ROM or read only network drive?

In windows:
- temp dir is defined and should be respected
- more is more.com, not more.exe, which might have something to do with process
creation.

hoijarvi: thanks!

Just noting for future reference that there are two mechanisms for passing
things through a pager: Darcs.External.viewDoc and Darcs.Utils.view_file

The former already defaults to printing on stdout; the latter does not.

The former is used for paging the --help output; the latter for printing patches
(I think)

And because the former uses pipeDoc, it attempts to create a temporary file. 
Now glancing at the temp file creation behaviour again.

In the meantime, you could try setting DARCS_TEMP

Note: the environment variable in question is DARCS_TMPDIR, but I get the
impression it won't have the intended effect.

Kari: thanks for your comments.  I see you have successfully experimented with
copying more.com to less.exe.  Could you run one more experiment for us; could
you run delete your less.exe (check that darcs fails) and then copy your
more.com to more.exe?

Thanks!

You're welcome.

more.exe did not work, it has to be less.exe. Capitalization did not 
matter, in windows it should not but I tested just in case.

In a related note:

Eric Kow wrote:
> Wait a second, I don't think this is a duplicate.  Is there any reason to
> believe that the diff-command stuff has anything to do with the pager?  I doubt it.
>
> ----------
> nosy: +eivuokko, jaredj, rgm, wglozer
> status: duplicate -> chatting
> title: if calling a pager fails, just print to stdout without a pager -> diff --diff-command => darcs: darcs84bdba: removeFile: permission denied (Permission denied)
> topic: +Windows
>   

My first though it that this is a pager issue. Somebody should test this 
under windows after making less.exe

Kari

Ok Kari, we've fixed the permissions and tmpdir issue, but we still need to
figure out what to do about the does-not-exist problem.  For what it's worth,
this works fine under Linux and MacOS X (we get an exit 127 which we catch), but
I'm guessing that under Windows, an exception is thrown which we also need to catch.

I can run Windows under Parallels, but it's a bit of pain.  Any Windows-using
Haskellers want to take this on?

The following patch updated the status of issue770 to be resolved:

* resolve issue770: catch 'does not exist' when running external programs 
Convert these errors into ExitCode 127 (for Windows)