Date: Wed, 22 Jun 2022 00:21:44 -0700
From: Noah Misch <noah@leadboat.com>
To: Andrew Dunstan <andrew@dunslane.net>
Cc: Michael Paquier <michael@paquier.xyz>, Tom Lane <tgl@sss.pgh.pa.us>,
	Andres Freund <andres@anarazel.de>, Erik Rijkers <er@xs4all.nl>,
	Robert Haas <robertmhaas@gmail.com>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>,
	Mark Dilger <mark.dilger@enterprisedb.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Postgres perl module namespace
Message-ID: <20220622072144.GD4167527@rfd.leadboat.com>
References: <20220418141530.nfxtkohefvwnzncl@alap3.anarazel.de>
 <20220418155224.GA1149931@rfd.leadboat.com>
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 <2361941.1650303832@sss.pgh.pa.us>
 <02188900-ba1e-8c6c-c7dd-98294f39c23f@dunslane.net>
 <2364418.1650305263@sss.pgh.pa.us>
 <f0d10209-7921-365a-aa7d-066e8cb8062e@dunslane.net>
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On Tue, Apr 19, 2022 at 07:24:58PM -0400, Andrew Dunstan wrote:
> On 2022-04-19 Tu 18:39, Michael Paquier wrote:
> > +*generate_ascii_string = *TestLib::generate_ascii_string;
> > +*slurp_dir = *TestLib::slurp_dir;
> > +*slurp_file = *TestLib::slurp_file;
> >
> > I am not sure if it is possible and my perl-fu is limited in this
> > area, but could a failure be enforced when loading this path if a new
> > routine added in TestLib.pm is forgotten in this list?
> 
> Not very easily that I'm aware of, but maybe some superior perl wizard
> will know better.

One can alias the symbol table, like https://metacpan.org/pod/Package::Alias
does.  I'm attaching what I plan to use.  Today, check-world fails after

  sed -i 's/TestLib/PostgreSQL::Test::Utils/g; s/PostgresNode/PostgreSQL::Test::Cluster/g' **/*.pl

on REL_14_STABLE, because today's alias list is incomplete.  With this change,
the same check-world passes.

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Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment; filename="alias-perl-symbol-tables-v1.patch"

Author:     Noah Misch <noah@leadboat.com>
Commit:     Noah Misch <noah@leadboat.com>

    For PostgreSQL::Test compatibility, alias entire package symbol tables.
    
    Remove the need to edit back-branch-specific code sites when
    back-patching the addition of a PostgreSQL::Test::Utils symbol.  Replace
    per-symbol, incomplete alias lists.  Give old and new package names the
    same EXPORT and EXPORT_OK semantics.  Back-patch to v10 (all supported
    versions).
    
    Reviewed by FIXME.
    
    Discussion: https://postgr.es/m/FIXME

diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 12339c2..a855fbc 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -1,9 +1,9 @@
 
 # Copyright (c) 2022, PostgreSQL Global Development Group
 
-# allow use of release 15+ perl namespace in older branches
-# just 'use' the older module name.
-# See PostgresNode.pm for function implementations
+# Allow use of release 15+ Perl package name in older branches, by giving that
+# package the same symbol table as the older package.  See PostgresNode::new
+# for behavior reacting to the class name.
 
 package PostgreSQL::Test::Cluster;
 
@@ -11,5 +11,8 @@ use strict;
 use warnings;
 
 use PostgresNode;
+BEGIN { *PostgreSQL::Test::Cluster:: = \*PostgresNode::; }
+
+use Exporter 'import';
 
 1;
diff --git a/src/test/perl/PostgreSQL/Test/Utils.pm b/src/test/perl/PostgreSQL/Test/Utils.pm
index bdbbd6e..e743bdf 100644
--- a/src/test/perl/PostgreSQL/Test/Utils.pm
+++ b/src/test/perl/PostgreSQL/Test/Utils.pm
@@ -1,48 +1,16 @@
 # Copyright (c) 2022, PostgreSQL Global Development Group
 
-# allow use of release 15+ perl namespace in older branches
-# just 'use' the older module name.
-# We export the same names as the v15 module.
-# See TestLib.pm for alias assignment that makes this all work.
+# Allow use of release 15+ Perl package name in older branches, by giving that
+# package the same symbol table as the older package.
 
 package PostgreSQL::Test::Utils;
 
 use strict;
 use warnings;
 
-use Exporter 'import';
-
 use TestLib;
+BEGIN { *PostgreSQL::Test::Utils:: = \*TestLib::; }
 
-our @EXPORT = qw(
-  generate_ascii_string
-  slurp_dir
-  slurp_file
-  append_to_file
-  check_mode_recursive
-  chmod_recursive
-  check_pg_config
-  dir_symlink
-  system_or_bail
-  system_log
-  run_log
-  run_command
-  pump_until
-
-  command_ok
-  command_fails
-  command_exit_is
-  program_help_ok
-  program_version_ok
-  program_options_handling_ok
-  command_like
-  command_like_safe
-  command_fails_like
-  command_checks_all
-
-  $windows_os
-  $is_msys2
-  $use_unix_sockets
-);
+use Exporter 'import';
 
 1;
diff --git a/src/test/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index be90963..5b8c7a9 100644
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -149,6 +149,11 @@ of finding port numbers, registering instances for cleanup, etc.
 sub new
 {
 	my ($class, $name, $pghost, $pgport) = @_;
+
+	# Use release 15+ semantics when called under a release 15+ name.
+	return PostgresNode->get_new_node(@_[ 1 .. $#_ ])
+	  if $class ne 'PostgresNode';
+
 	my $testname = basename($0);
 	$testname =~ s/\.[^.]+$//;
 	my $self = {
@@ -2796,18 +2801,4 @@ sub corrupt_page_checksum
 
 =cut
 
-# support release 15+ perl module namespace
-
-package PostgreSQL::Test::Cluster; ## no critic (ProhibitMultiplePackages)
-
-sub new
-{
-	shift; # remove class param from args
-	return PostgresNode->get_new_node(@_);
-}
-
-no warnings 'once';
-
-*get_free_port = *PostgresNode::get_free_port;
-
 1;
diff --git a/src/test/perl/TestLib.pm b/src/test/perl/TestLib.pm
index f3ee20a..610050e 100644
--- a/src/test/perl/TestLib.pm
+++ b/src/test/perl/TestLib.pm
@@ -979,46 +979,4 @@ sub command_checks_all
 
 =cut
 
-# support release 15+ perl module namespace
-
-package PostgreSQL::Test::Utils; ## no critic (ProhibitMultiplePackages)
-
-# we don't want to export anything here, but we want to support things called
-# via this package name explicitly.
-
-# use typeglobs to alias these functions and variables
-
-no warnings qw(once);
-
-*generate_ascii_string = *TestLib::generate_ascii_string;
-*slurp_dir = *TestLib::slurp_dir;
-*slurp_file = *TestLib::slurp_file;
-*append_to_file = *TestLib::append_to_file;
-*check_mode_recursive = *TestLib::check_mode_recursive;
-*chmod_recursive = *TestLib::chmod_recursive;
-*check_pg_config = *TestLib::check_pg_config;
-*dir_symlink = *TestLib::dir_symlink;
-*system_or_bail = *TestLib::system_or_bail;
-*system_log = *TestLib::system_log;
-*run_log = *TestLib::run_log;
-*run_command = *TestLib::run_command;
-*command_ok = *TestLib::command_ok;
-*command_fails = *TestLib::command_fails;
-*command_exit_is = *TestLib::command_exit_is;
-*program_help_ok = *TestLib::program_help_ok;
-*program_version_ok = *TestLib::program_version_ok;
-*program_options_handling_ok = *TestLib::program_options_handling_ok;
-*command_like = *TestLib::command_like;
-*command_like_safe = *TestLib::command_like_safe;
-*command_fails_like = *TestLib::command_fails_like;
-*command_checks_all = *TestLib::command_checks_all;
-
-*windows_os = *TestLib::windows_os;
-*is_msys2 = *TestLib::is_msys2;
-*use_unix_sockets = *TestLib::use_unix_sockets;
-*timeout_default = *TestLib::timeout_default;
-*tmp_check = *TestLib::tmp_check;
-*log_path = *TestLib::log_path;
-*test_logfile = *TestLib::test_log_file;
-
 1;

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