fix: return the mapped document type for an empty id

src/Database/Database.php

@@ -4911,7 +4911,7 @@ public function getDocument(string $collection, string $id, array $queries = [],
         }
 
         if (empty($id)) {
-            return new Document();
+            return $this->createDocumentInstance($collection, []);
         }
 
         $collection = $this->silent(fn () => $this->getCollection($collection));

tests/unit/EmptyDocumentTypeTest.php

@@ -0,0 +1,54 @@
+<?php
+
+namespace Tests\Unit;
+
+use PHPUnit\Framework\TestCase;
+use Utopia\Cache\Adapter\Memory as CacheMemory;
+use Utopia\Cache\Cache;
+use Utopia\Database\Adapter\Memory as DatabaseMemory;
+use Utopia\Database\Database;
+use Utopia\Database\Document;
+
+class TypedUser extends Document
+{
+}
+
+class EmptyDocumentTypeTest extends TestCase
+{
+    /**
+     * A caller that passes the type hint of the mapped class along (an HTTP
+     * resource returning the current user, say) must be able to rely on every
+     * empty result being that class, including the one for an empty id, which
+     * short-circuits before the collection is even looked up.
+     */
+    public function testEmptyIdReturnsTheMappedDocumentType(): void
+    {
+        $database = new Database(new DatabaseMemory(), new Cache(new CacheMemory()));
+        $database
+            ->setDatabase('utopiaTests')
+            ->setNamespace('empty_type_' . \uniqid());
+        $database->create();
+        $database->createCollection('users');
+        $database->setDocumentType('users', TypedUser::class);
+
+        $empty = $database->getDocument('users', '');
+
+        $this->assertInstanceOf(TypedUser::class, $empty);
+        $this->assertTrue($empty->isEmpty());
+
+        $missing = $database->getDocument('users', 'nobody');
+
+        $this->assertInstanceOf(TypedUser::class, $missing);
+        $this->assertTrue($missing->isEmpty());
+    }
+
+    public function testEmptyIdOnAnUnmappedCollectionStaysAPlainDocument(): void
+    {
+        $database = new Database(new DatabaseMemory(), new Cache(new CacheMemory()));
+
+        $empty = $database->getDocument('anything', '');
+
+        $this->assertSame(Document::class, $empty::class);
+        $this->assertTrue($empty->isEmpty());
+    }
+}