[PATCH 3/3] lei: don't gzip --rsyncable by default for mbox*

[Eric Wong <e@80x24.org>]

Using and memoizing the usability of `--rsyncable' is unsafe
since pigz (or GNU gzip) can be uninstalled and leave a user
with a non-rsync-aware gzip implementation in the long-running
daemon.  So we stop passing --rsyncable by default to pigz/gzip
and no longer attempt to check for it (since it was a TOCTTOU
error, anyways).

Specifying --rsyncable explicitly didn't work, either, and
ended up passing `1' to the gzip/pigz argv :x

Finally, we now test --rsyncable on the CLI by adding support
for it in `lei convert' and testing it in t/lei-convert.t
---
 lib/PublicInbox/LEI.pm        |  3 ++-
 lib/PublicInbox/LeiToMail.pm  |  2 +-
 lib/PublicInbox/MboxReader.pm | 36 ++++++++---------------------------
 t/lei-convert.t               | 27 ++++++++++++++++++++++++--
 4 files changed, 36 insertions(+), 32 deletions(-)

diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index 2f8d7a96..beb0f897 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -275,7 +275,8 @@ our %CMD = ( # sorted in order of importance/use:
 	qw(all:s mode=s), @net_opt, @c_opt ],
 'convert' => [ 'LOCATION...|--stdin',
 	'one-time conversion from URL or filesystem to another format',
-	qw(stdin| in-format|F=s out-format|f=s output|mfolder|o=s lock=s@ kw!),
+	qw(stdin| in-format|F=s out-format|f=s output|mfolder|o=s lock=s@ kw!
+		rsyncable),
 	@net_opt, @c_opt ],
 'p2q' => [ 'LOCATION_OR_COMMIT...|--stdin',
 	"use a patch to generate a query for `lei q --stdin'",
diff --git a/lib/PublicInbox/LeiToMail.pm b/lib/PublicInbox/LeiToMail.pm
index a2cd8650..2dddf00b 100644
--- a/lib/PublicInbox/LeiToMail.pm
+++ b/lib/PublicInbox/LeiToMail.pm
@@ -155,7 +155,7 @@ sub reap_compress { # awaitpid callback
 	$lei->fail($?, "@$cmd failed") if $?;
 }
 
-sub _post_augment_mbox { # open a compressor process from top-level process
+sub _post_augment_mbox { # open a compressor process from top-level lei-daemon
 	my ($self, $lei) = @_;
 	my $zsfx = $self->{zsfx} or return;
 	my $cmd = PublicInbox::MboxReader::zsfx2cmd($zsfx, undef, $lei);
diff --git a/lib/PublicInbox/MboxReader.pm b/lib/PublicInbox/MboxReader.pm
index beffabe8..e4209022 100644
--- a/lib/PublicInbox/MboxReader.pm
+++ b/lib/PublicInbox/MboxReader.pm
@@ -1,10 +1,10 @@
-# Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 
-# reader for mbox variants we support
+# reader for mbox variants we support (and also sets up commands for writing)
 package PublicInbox::MboxReader;
 use strict;
-use v5.10.1;
+use v5.10.1; # check regexps before v5.12
 use Data::Dumper;
 $Data::Dumper::Useqq = 1; # should've been the default, for bad data
 
@@ -141,10 +141,9 @@ sub reads {
 
 # all of these support -c for stdout and -d for decompression,
 # mutt is commonly distributed with hooks for gz, bz2 and xz, at least
-# { foo => '' } means "--foo" is passed to the command-line,
-# otherwise { foo => '--bar' } passes "--bar"
+# { foo => '' } means "--foo" is passed to the command-line
 my %zsfx2cmd = (
-	gz => [ qw(GZIP pigz gzip) ],
+	gz => [ qw(GZIP pigz gzip), { rsyncable => '' } ],
 	bz2 => [ 'bzip2', {} ],
 	xz => [ 'xz', {} ],
 	# don't add new entries here unless MUA support is widely available
@@ -173,28 +172,9 @@ sub zsfx2cmd ($$$) {
 	}
 	$cmd[0] // die join(' or ', @info)." missing for .$zsfx";
 
-	# not all gzip support --rsyncable, FreeBSD gzip doesn't even exit
-	# with an error code
-	if (!$decompress && $cmd[0] =~ m!/gzip\z! && !defined($cmd_opt)) {
-		pipe(my ($r, $w)) or die "pipe: $!";
-		open my $null, '+>', '/dev/null' or die "open: $!";
-		my $rdr = { 0 => $null, 1 => $null, 2 => $w };
-		my $tst = [ $cmd[0], '--rsyncable' ];
-		my $pid = PublicInbox::Spawn::spawn($tst, undef, $rdr);
-		close $w;
-		my $err = do { local $/; <$r> };
-		waitpid($pid, 0) == $pid or die "BUG: waitpid: $!";
-		$cmd_opt = $err ? {} : { rsyncable => '' };
-		push(@$x, $cmd_opt);
-	}
-	for my $bool (keys %$cmd_opt) {
-		my $switch = $cmd_opt->{$bool} // next;
-		push @cmd, '--'.($switch || $bool);
-	}
-	for my $key (qw(rsyncable)) { # support compression level?
-		my $switch = $cmd_opt->{$key} // next;
-		my $val = $lei->{opt}->{$key} // next;
-		push @cmd, $switch, $val;
+	# only for --rsyncable.  TODO: support compression level?
+	for my $key (keys %$cmd_opt) {
+		push @cmd, '--'.$key if $lei->{opt}->{$key};
 	}
 	\@cmd;
 }
diff --git a/t/lei-convert.t b/t/lei-convert.t
index e1849ff7..115e7ed0 100644
--- a/t/lei-convert.t
+++ b/t/lei-convert.t
@@ -1,12 +1,13 @@
 #!perl -w
-# Copyright (C) 2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
-use strict; use v5.10.1; use PublicInbox::TestCommon;
+use v5.12; use PublicInbox::TestCommon;
 use PublicInbox::MboxReader;
 use PublicInbox::MdirReader;
 use PublicInbox::NetReader;
 use PublicInbox::Eml;
 use IO::Uncompress::Gunzip;
+use autodie qw(open);
 require_mods(qw(lei -imapd -nntpd Mail::IMAPClient Net::NNTP));
 my ($tmpdir, $for_destroy) = tmpdir;
 my $sock = tcp_server;
@@ -125,5 +126,27 @@ test_lei({ tmpdir => $tmpdir }, sub {
 	like($md[0], qr/:2,S\z/, "`seen' flag set in Maildir");
 	lei_ok(qw(convert -o mboxrd:/dev/stdout), "$d/md2");
 	like($lei_out, qr/^Status: RO/sm, "`seen' flag preserved");
+
+	SKIP: {
+		my $ok;
+		for my $x (($ENV{GZIP}//''), qw(pigz gzip)) {
+			$x && `$x -h 2>&1` =~ /--rsyncable\b/s or next;
+			$ok = $x;
+			last;
+		}
+		skip 'pigz || gzip do not support --rsyncable' if !$ok;
+		lei_ok qw(convert --rsyncable), "mboxrd:$d/qp.gz",
+			'-o', "mboxcl2:$d/qp2.gz";
+		undef $fh; # necessary to make IO::Uncompress::Gunzip happy
+		open $fh, '<', "$d/qp2.gz";
+		$fh = IO::Uncompress::Gunzip->new($fh, MultiStream => 1);
+		my @tmp;
+		PublicInbox::MboxReader->mboxcl2($fh, sub {
+			my ($eml) = @_;
+			$eml->header_set($_) for qw(Content-Length Lines);
+			push @tmp, $eml;
+		});
+		is_deeply(\@tmp, \@bar, 'read rsyncable-gzipped mboxcl2');
+	}
 });
 done_testing;