From: ilmari@ilmari.org (Dagfinn Ilmari =?utf-8?Q?Manns=C3=A5ker?=)
To: Juan =?utf-8?Q?Jos=C3=A9_Santamar=C3=ADa_Flecha?=
 <juanjo.santamaria@gmail.com>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
  Michael Paquier <michael@paquier.xyz>,
  pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: TAP tests and symlinks on Windows
References: <c50a646c-d9bb-7c62-a4bf-8256ff6ff338@2ndquadrant.com>
	<20200609071931.GE38342@paquier.xyz>
	<89a38304-8900-2e6b-de26-19a0312f3a87@2ndquadrant.com>
	<CAC+AXB3NfdDsp+egpYj=qgD+vPhb_dNRA4vwgcTL+Vmhj38UWw@mail.gmail.com>
Date: Tue, 09 Jun 2020 11:26:19 +0100
In-Reply-To: 
 <CAC+AXB3NfdDsp+egpYj=qgD+vPhb_dNRA4vwgcTL+Vmhj38UWw@mail.gmail.com>
	("Juan =?utf-8?Q?Jos=C3=A9_Santamar=C3=ADa?= Flecha"'s message of "Tue, 9
 Jun 2020 09:33:32
	+0200")
Message-ID: <87sgf4pmb8.fsf@wibble.ilmari.org>
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Juan José Santamaría Flecha <juanjo.santamaria@gmail.com> writes:

> On Tue, Jun 9, 2020 at 9:28 AM Peter Eisentraut <
> peter.eisentraut@2ndquadrant.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/004_pg_xlog_symlink.pl 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:

    https://metacpan.org/source/AUDREYT/Win32-Symlink-0.06/pgsymlink.c

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.
    BEGIN {
        eval { require Win32::Symlink; Win32::Symlink->import; }
    }

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