From e28af9a5a7d41fe6bf240a3f51165f95acc5a98a Mon Sep 17 00:00:00 2001
From: Loz Calver <lozcalver@bigfork.co.uk>
Date: Mon, 4 Dec 2023 11:28:51 +0000
Subject: [PATCH 1/2] FIX: UnsavedRelationList first/last to return null if
 list is empty (fixes #11083)

---
 src/ORM/UnsavedRelationList.php           |  8 ++++----
 tests/php/ORM/UnsavedRelationListTest.php | 16 ++++++++++++++++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/ORM/UnsavedRelationList.php b/src/ORM/UnsavedRelationList.php
index 51cde920fd9..4a6a702f296 100644
--- a/src/ORM/UnsavedRelationList.php
+++ b/src/ORM/UnsavedRelationList.php
@@ -239,11 +239,11 @@ public function getIDList()
      */
     public function first()
     {
-        $item = reset($this->items);
+        $item = reset($this->items) ?: null;
         if (is_numeric($item)) {
             $item = DataObject::get_by_id($this->dataClass, $item);
         }
-        if (!empty($this->extraFields[key($this->items)])) {
+        if ($item && !empty($this->extraFields[key($this->items)])) {
             $item->update($this->extraFields[key($this->items)]);
         }
         return $item;
@@ -256,8 +256,8 @@ public function first()
      */
     public function last()
     {
-        $item = end($this->items);
-        if (!empty($this->extraFields[key($this->items)])) {
+        $item = end($this->items) ?: null;
+        if ($item && !empty($this->extraFields[key($this->items)])) {
             $item->update($this->extraFields[key($this->items)]);
         }
         return $item;
diff --git a/tests/php/ORM/UnsavedRelationListTest.php b/tests/php/ORM/UnsavedRelationListTest.php
index 7a8955f2d42..5c6559c51c3 100644
--- a/tests/php/ORM/UnsavedRelationListTest.php
+++ b/tests/php/ORM/UnsavedRelationListTest.php
@@ -310,4 +310,20 @@ public function testColumn()
             ]
         );
     }
+
+    public function testFirstAndLast()
+    {
+        $object = new UnsavedRelationListTest\TestObject();
+        $children = $object->Children();
+
+        $this->assertNull($children->first(), 'Empty UnsavedRelationList should return null for first item.');
+        $this->assertNull($children->last(), 'Empty UnsavedRelationList should return null for last item.');
+
+        $children->add($firstChild = $this->objFromFixture(UnsavedRelationListTest\TestObject::class, 'ObjectA'));
+        $children->add($this->objFromFixture(UnsavedRelationListTest\TestObject::class, 'ObjectB'));
+        $children->add($lastChild = $this->objFromFixture(UnsavedRelationListTest\TestObject::class, 'ObjectC'));
+
+        $this->assertEquals($firstChild, $children->first(), 'Incorrect first item in UnsavedRelationList.');
+        $this->assertEquals($lastChild, $children->last(), 'Incorrect last item in UnsavedRelationList.');
+    }
 }

From 40b888eaf30f6c6899134f7fcbfb0705987516e1 Mon Sep 17 00:00:00 2001
From: Loz Calver <lozcalver@bigfork.co.uk>
Date: Mon, 4 Dec 2023 11:44:34 +0000
Subject: [PATCH 2/2] FIX: UnsavedRelationList::last() sometimes returned an ID
 instead of an item

---
 src/ORM/UnsavedRelationList.php | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/ORM/UnsavedRelationList.php b/src/ORM/UnsavedRelationList.php
index 4a6a702f296..9e078c63e47 100644
--- a/src/ORM/UnsavedRelationList.php
+++ b/src/ORM/UnsavedRelationList.php
@@ -257,6 +257,9 @@ public function first()
     public function last()
     {
         $item = end($this->items) ?: null;
+        if (is_numeric($item)) {
+            $item = DataObject::get_by_id($this->dataClass, $item);
+        }
         if ($item && !empty($this->extraFields[key($this->items)])) {
             $item->update($this->extraFields[key($this->items)]);
         }