From 22221feaa273dec75d23732933ea29b51e031044 Mon Sep 17 00:00:00 2001
From: Pedro Amorim <pedro.amorim@openfifth.co.uk>
Date: Tue, 14 Jul 2026 09:27:21 +0000
Subject: [PATCH] Bug 43069: Don't match every patron when no duplicate-match
 fields apply

check_for_existing_matches() called Koha::Patrons->search(undef) when
PatronDuplicateMatchingAddFields left no usable field to match on,
which matches every patron instead of none.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@openfifth.co.uk>
Signed-off-by: Pedro Amorim <pedro.amorim@openfifth.co.uk>
---
 Koha/Patrons.pm | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Koha/Patrons.pm b/Koha/Patrons.pm
index 2bafea19ea..425893e8d4 100644
--- a/Koha/Patrons.pm
+++ b/Koha/Patrons.pm
@@ -749,6 +749,10 @@ sub check_for_existing_matches {
         $match_conditions->{$field} = $new_patron_data->{$field} if $new_patron_data->{$field};
     }
 
+    # Without any usable conditions, Koha::Patrons->search would run
+    # unfiltered and match every patron in the system.
+    return { 'duplicate_found' => 0 } unless $match_conditions && %$match_conditions;
+
     my $patrons = Koha::Patrons->search($match_conditions);
     if ( $patrons->count > 0 ) {
         return {