Trigger warning when calling CodecCursor::setTypeMap

src/Model/CodecCursor.php

@@ -27,6 +27,10 @@
 
 use function assert;
 use function iterator_to_array;
+use function sprintf;
+use function trigger_error;
+
+use const E_USER_WARNING;
 
 /**
  * @template TValue of object
@@ -104,6 +108,7 @@ public function rewind(): void
     public function setTypeMap(array $typemap): void
     {
         // Not supported
+        trigger_error(sprintf('Discarding type map for %s', __METHOD__), E_USER_WARNING);
     }
 
     /** @return array<int, TValue> */

tests/Model/CodecCursorFunctionalTest.php

@@ -0,0 +1,66 @@
+<?php
+
+namespace MongoDB\Tests\Model;
+
+use MongoDB\BSON\Document;
+use MongoDB\Codec\DocumentCodec;
+use MongoDB\Model\CodecCursor;
+use MongoDB\Tests\FunctionalTestCase;
+
+class CodecCursorFunctionalTest extends FunctionalTestCase
+{
+    public function setUp(): void
+    {
+        parent::setUp();
+
+        $this->dropCollection($this->getDatabaseName(), $this->getCollectionName());
+    }
+
+    public function testSetTypeMap(): void
+    {
+        $collection = self::createTestClient()->selectCollection($this->getDatabaseName(), $this->getCollectionName());
+        $cursor = $collection->find();
+
+        $codecCursor = CodecCursor::fromCursor($cursor, $this->createCodec());
+
+        $this->expectWarning();
+        $this->expectWarningMessage('Discarding type map for MongoDB\Model\CodecCursor::setTypeMap');
+
+        $codecCursor->setTypeMap(['root' => 'array']);
+    }
+
+    private function createCodec(): DocumentCodec
+    {
+        return new class implements DocumentCodec {
+            public function canDecode($value): bool
+            {
+                return false;
+            }
+
+            public function canEncode($value): bool
+            {
+                return false;
+            }
+
+            public function decode($value): object
+            {
+                return (object) [];
+            }
+
+            public function decodeIfSupported($value): object
+            {
+                return (object) [];
+            }
+
+            public function encode($value): Document
+            {
+                return Document::fromPHP([]);
+            }
+
+            public function encodeIfSupported($value): Document
+            {
+                return Document::fromPHP([]);
+            }
+        };
+    }
+}