Prevent redirecting an entity to itself

Bug: T214920

Author: Ladsgroup

src/Entity/EntityRedirect.php

@@ -37,6 +37,10 @@ public function __construct( EntityId $entityId, EntityId $targetId ) {
 			);
 		}
 
+		if ( $entityId->getSerialization() === $targetId->getSerialization() ) {
+			throw new InvalidArgumentException( '$entityId and $targetId can not be the same.' );
+		}
+
 		$this->entityId = $entityId;
 		$this->targetId = $targetId;
 	}

tests/unit/Entity/EntityRedirectTest.php

@@ -37,6 +37,15 @@ public function testConstruction_baseType() {
 		new EntityRedirect( $entityId, $targetId );
 	}
 
+	public function testConstruction_sameEntity() {
+		$this->expectException( InvalidArgumentException::class );
+
+		$entityId = new ItemId( 'Q123' );
+		$targetId = new ItemId( 'Q123' );
+
+		new EntityRedirect( $entityId, $targetId );
+	}
+
 	public function equalsProvider() {
 		$q123 = new ItemId( 'Q123' );
 		$q345 = new ItemId( 'Q345' );