[PATCH] imap: quiet Parse::RecDescent errors on bad search queries

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

Parse::RecDescent emits giant errors to STDERR by default
(bypassing $SIG{__WARN__}, even).  Shut it up since there's
no good way to pass those back to a client, and we don't want
clients flooding logs with bogus requests.
---
 lib/PublicInbox/IMAPsearchqp.pm | 4 +++-
 t/imap_searchqp.t               | 6 +++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/lib/PublicInbox/IMAPsearchqp.pm b/lib/PublicInbox/IMAPsearchqp.pm
index 9f0c1205..0c37220c 100644
--- a/lib/PublicInbox/IMAPsearchqp.pm
+++ b/lib/PublicInbox/IMAPsearchqp.pm
@@ -1,4 +1,4 @@
-# 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>
 # IMAP search query parser.  cf RFC 3501
 
@@ -279,6 +279,8 @@ sub parse {
 	my $sql = '';
 	%$q = (sql => \$sql, imap => $imap); # imap = PublicInbox::IMAP obj
 	# $::RD_TRACE = 1;
+	local $::RD_ERRORS = undef;
+	local $::RD_WARN = undef;
 	my $res = eval { $prd->search_key(uc($query)) };
 	return $@ if $@ && $@ =~ /\A(?:BAD|NO) /;
 	return 'BAD unexpected result' if !$res || $res != $q;
diff --git a/t/imap_searchqp.t b/t/imap_searchqp.t
index e2f49e5a..968d4329 100644
--- a/t/imap_searchqp.t
+++ b/t/imap_searchqp.t
@@ -1,5 +1,5 @@
 #!perl -w
-# Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict;
 use v5.10.1;
@@ -29,10 +29,10 @@ is($q->{xap}, 'f:"b"', 'charset handled');
 $q = $parse->(qq{CHARSET WTF-8 From b});
 like($q, qr/\ANO \[/, 'bad charset rejected');
 {
-	# TODO: squelch errors by default? clients could flood logs
-	open my $fh, '>:scalar', \(my $buf) or die;
+	open my $fh, '>:scalar', \(my $buf = '') or die;
 	local *STDERR = $fh;
 	$q = $parse->(qq{CHARSET});
+	is($buf, '', 'nothing spewed to STDERR on bad query');
 }
 like($q, qr/\ABAD /, 'bad charset rejected');