Re: TAP tests and symlinks on Windows

From: ilmari(at)ilmari(dot)org (Dagfinn Ilmari Mannsåker )
To: Juan José Santamaría Flecha <juanjo(dot)santamaria(at)gmail(dot)com>
Cc: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: TAP tests and symlinks on Windows
Date: 2020-06-09 10:26:19
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Juan José Santamaría Flecha <juanjo(dot)santamaria(at)gmail(dot)com> writes:

> On Tue, Jun 9, 2020 at 9:28 AM Peter Eisentraut <
> peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
>> On 2020-06-09 09:19, Michael Paquier wrote:
>> > On Mon, Jun 08, 2020 at 02:44:31PM +0200, Peter Eisentraut wrote:
>> >> both contain a TAP skip notice "symlinks not supported on Windows".
>> >>
>> >> This is untrue. Symlinks certainly work on Windows, and we have other
>> TAP
>> >> tests using them, for example for tablespaces.
>> >
>> >> pg_rewind/t/ passes for me on Windows if I just
>> remove
>> >> the skip stuff. My attached patch does that.
>> >
>> > What's the version of your perl installation on Windows? With 5.22, I
>> > am still seeing that symlink() is not implemented, causing the tests
>> > of pg_rewind to blow in flight with your patch (MSVC 2015 here).
>> I was using MSYS2 and the Perl version appears to have been 5.30.2.
>> Note sure which one of these two factors makes the difference.
> The difference seems to be MSYS2, it also fails for me if I do not
> include 'Win32::Symlink' with Perl 5.30.2.

Amusingly, Win32::Symlink uses a copy of our pgsymlink(), which emulates
symlinks via junction points:

A portable way of using symlinks if possible would be:

# In a BEGIN block because it overrides CORE::GLOBAL::symlink, which
# only takes effect on code that's compiled after the override is
# installed. We don't care if it fails, since it works without on
# some Windows perls.
eval { require Win32::Symlink; Win32::Symlink->import; }

# symlink() throws an exception if t
if (not eval { symlink("",""); 1; })
plan skip_all => 'symlinks not supported';
plan tests => 5;

Plus a note in the Win32 docs that Win32::Symlink may be required to run
some tests on some Perl/Windows versions..

- ilmari
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