From 9e39fec0df7d72e94e3dbaf57681755639f558f4 Mon Sep 17 00:00:00 2001
From: Adam Wood <72983627+webmaster-cses-org-uk@users.noreply.github.com>
Date: Wed, 3 Nov 2021 21:04:23 +0000
Subject: [PATCH 1/3] Resolve error on empty multiple-contact field

This change removes a potential "getFieldValue failed" error that can be thrown if an empty scalar value occurs in a multiple-contact reference custom field.

See https://lab.civicrm.org/dev/core/-/issues/2939
---
 CRM/Core/BAO/CustomField.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CRM/Core/BAO/CustomField.php b/CRM/Core/BAO/CustomField.php
index 2ca7070c76cb..5f6dbee42865 100644
--- a/CRM/Core/BAO/CustomField.php
+++ b/CRM/Core/BAO/CustomField.php
@@ -1069,7 +1069,7 @@ private static function formatDisplayValue($value, $field, $entityId = NULL) {
       case 'Autocomplete-Select':
       case 'Radio':
       case 'CheckBox':
-        if ($field['data_type'] == 'ContactReference' && (is_array($value) || is_numeric($value))) {
+        if ($field['data_type'] == 'ContactReference' && (is_array($value) || is_numeric($value)) && !empty($value)) {
           $displayNames = [];
           foreach ((array) $value as $contactId) {
             $displayNames[] = CRM_Core_DAO::getFieldValue('CRM_Contact_DAO_Contact', $contactId, 'display_name');

From 66102b8ca4bdd520504c2ab1578e6505c73bf174 Mon Sep 17 00:00:00 2001
From: Adam Wood <72983627+webmaster-cses-org-uk@users.noreply.github.com>
Date: Wed, 3 Nov 2021 21:27:13 +0000
Subject: [PATCH 2/3] Improve previous fix to avoid returning non-string

Further to previous commit, update to avoid returning non-string from method while still protecting against empty input values for multi-valued contact field.
---
 CRM/Core/BAO/CustomField.php | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/CRM/Core/BAO/CustomField.php b/CRM/Core/BAO/CustomField.php
index 5f6dbee42865..e1f333295d8c 100644
--- a/CRM/Core/BAO/CustomField.php
+++ b/CRM/Core/BAO/CustomField.php
@@ -1069,12 +1069,19 @@ private static function formatDisplayValue($value, $field, $entityId = NULL) {
       case 'Autocomplete-Select':
       case 'Radio':
       case 'CheckBox':
-        if ($field['data_type'] == 'ContactReference' && (is_array($value) || is_numeric($value)) && !empty($value)) {
-          $displayNames = [];
-          foreach ((array) $value as $contactId) {
-            $displayNames[] = CRM_Core_DAO::getFieldValue('CRM_Contact_DAO_Contact', $contactId, 'display_name');
+        if ($field['data_type'] == 'ContactReference' && (is_array($value) || is_numeric($value))) {
+          if (empty($value))
+          {
+            $display = '';
+          }
+          else
+          {
+            $displayNames = [];
+            foreach ((array) $value as $contactId) {
+              $displayNames[] = CRM_Core_DAO::getFieldValue('CRM_Contact_DAO_Contact', $contactId, 'display_name');
+            }
+            $display = implode(', ', $displayNames);
           }
-          $display = implode(', ', $displayNames);
         }
         elseif ($field['data_type'] == 'ContactReference') {
           $display = $value;

From 627d36b7c218e7bd7447a2dca8e84b96491dd55e Mon Sep 17 00:00:00 2001
From: Adam Wood <72983627+webmaster-cses-org-uk@users.noreply.github.com>
Date: Wed, 3 Nov 2021 21:36:53 +0000
Subject: [PATCH 3/3] Updated proposed addition to house coding style

---
 CRM/Core/BAO/CustomField.php | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/CRM/Core/BAO/CustomField.php b/CRM/Core/BAO/CustomField.php
index e1f333295d8c..644f16fcffe6 100644
--- a/CRM/Core/BAO/CustomField.php
+++ b/CRM/Core/BAO/CustomField.php
@@ -1070,12 +1070,10 @@ private static function formatDisplayValue($value, $field, $entityId = NULL) {
       case 'Radio':
       case 'CheckBox':
         if ($field['data_type'] == 'ContactReference' && (is_array($value) || is_numeric($value))) {
-          if (empty($value))
-          {
+          if (empty($value)) {
             $display = '';
           }
-          else
-          {
+          else {
             $displayNames = [];
             foreach ((array) $value as $contactId) {
               $displayNames[] = CRM_Core_DAO::getFieldValue('CRM_Contact_DAO_Contact', $contactId, 'display_name');