From 3bd160559babcf4fb8c8dd83815992e8e12ca2de Mon Sep 17 00:00:00 2001
From: Connor Tumbleson <connor@sourcetoad.com>
Date: Wed, 25 Nov 2020 12:05:57 -0500
Subject: [PATCH 1/2] fix: use strict null check on morphTo type

---
 src/Illuminate/Database/Eloquent/Concerns/HasRelationships.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Illuminate/Database/Eloquent/Concerns/HasRelationships.php b/src/Illuminate/Database/Eloquent/Concerns/HasRelationships.php
index 049f3b294365..b8e8bcf01adb 100644
--- a/src/Illuminate/Database/Eloquent/Concerns/HasRelationships.php
+++ b/src/Illuminate/Database/Eloquent/Concerns/HasRelationships.php
@@ -256,7 +256,7 @@ public function morphTo($name = null, $type = null, $id = null, $ownerKey = null
         // If the type value is null it is probably safe to assume we're eager loading
         // the relationship. In this case we'll just pass in a dummy query where we
         // need to remove any eager loads that may already be defined on a model.
-        return empty($class = $this->{$type})
+        return is_null($class = $this->{$type})
                     ? $this->morphEagerTo($name, $type, $id, $ownerKey)
                     : $this->morphInstanceTo($class, $name, $type, $id, $ownerKey);
     }

From 4a055e72cba9f86cf5da0daf36779f63d3589a5c Mon Sep 17 00:00:00 2001
From: Connor Tumbleson <connor@sourcetoad.com>
Date: Wed, 25 Nov 2020 12:06:23 -0500
Subject: [PATCH 2/2] test: assert 0 relation_type is handled correctly

---
 tests/Database/DatabaseEloquentMorphToTest.php | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tests/Database/DatabaseEloquentMorphToTest.php b/tests/Database/DatabaseEloquentMorphToTest.php
index 67c584e0fe4e..3f466054e4b5 100644
--- a/tests/Database/DatabaseEloquentMorphToTest.php
+++ b/tests/Database/DatabaseEloquentMorphToTest.php
@@ -90,6 +90,16 @@ public function testMorphToWithArrayDefault()
         $this->assertSame('taylor', $result->username);
     }
 
+    public function testMorphToWithZeroMorphType()
+    {
+        $parent = $this->getMockBuilder(EloquentMorphToModelStub::class)->onlyMethods(['getAttribute', 'morphEagerTo', 'morphInstanceTo'])->getMock();
+        $parent->method('getAttribute')->with('relation_type')->willReturn(0);
+        $parent->expects($this->once())->method('morphInstanceTo');
+        $parent->expects($this->never())->method('morphEagerTo');
+
+        $parent->relation();
+    }
+
     public function testMorphToWithSpecifiedClassDefault()
     {
         $parent = new EloquentMorphToModelStub;