bug#20242: 24.5; compilation-mode and tramp interaction bug

[Michael Albinus <michael.albinus@gmx.de>]

David Hull <david.hull@openx.com> writes:

Hi David,

> I believe that there is a bug in the interaction between
> compilation-mode and tramp.  This bug exists in 24.5rc1, but also exists
> in the previous emacs version, 24.4.1.  This is the situation:
>
> I am running emacs on a Mac.  On the Mac, "/var" is a symlink to
> "private/var".
>
> I am using tramp to visit a project on a CentOS 6 VM.  The project on
> the VM is in "/var/home/david.hull/src/ds-advertiser-server/src".
>
> I run "M-x compile", and run "make -k" as the compilation command.
> Compile creates a "*compilation*" buffer with the error messages.  Here
> are the partial contents, prefixed with ">":
>
>> -*- mode: compilation; default-directory:
>> "/scp:cos6:/var/home/david.hull/src/ds-advertiser-server/src/" -*-
>> Compilation started at Wed Apr  1 10:18:47
>> 
>> ds_adv_ox3_ad_v5.erl:44: syntax error before: '}'
>
> When I press Enter on this error line to run compile-goto-error, I get
> the following message in the minibuffer:
>
> Find this error in (default ds_adv_ox3_ad_v5.erl):
> /scp:cos6:/private/var/home/david.hull/src/ds-advertiser-server/src
>
> Note that the file path begins with "/private/var" instead of "/var".  I
> believe that either compilation-mode or tramp is attempting to expand
> the symlinks, but is incorrectly expanding "/var" to "/private/var",
> which would be correct on the Mac but is incorrect on the CentOS VM.

I cannot reproduce the error, neither with Emacs 24.5 RC3, nor with
Emacs 25.0.50. I have applied the following steps:

- On the local machine:

  mkdir /tmp/foo
  ln -s /tmp/foo /foo

- On the remote machine:

  mkdir /foo
  echo "(require 'foo)" >/foo/foo.el

- Then I have opened /scp:machine:/foo/foo.el. I have applied "M-x compile RET
  emacs --no-site-file -batch -l bytecomp -f batch-byte-compile foo.el".

The result was the *compilation* buffer

--8<---------------cut here---------------start------------->8---
-*- mode: compilation; default-directory: "/scp:machine:/foo/" -*-
Compilation started at Mon Apr  6 11:18:14

emacs --no-site-file -batch -l bytecomp -f batch-byte-compile foo.el

In toplevel form:
foo.el:1:1:Error: Cannot open load file: foo

Compilation exited abnormally with code 1 at Mon Apr  6 11:18:15
--8<---------------cut here---------------end--------------->8---

When I apply "M-x compile-goto-error" on the error line, file
/scp:machine:/foo/foo.el is opened as expected.

Maybe you have some nasty local settings? Could you reproduce the
problem when starting "emacs -Q"?

> Thanks.

Best regards, Michael.