allow promise to be returned in methods

Author: Andrii Sudiev

Diff for: src/QueryField.php

@@ -74,15 +74,7 @@ public function __construct(
             $callResolver = function (...$args) use ($originalResolver, $source, $resolver) {
                 $result = $resolver($source, ...$args);
 
-                try {
-                    $this->assertReturnType($result);
-                } catch (TypeMismatchRuntimeException $e) {
-                    $e->addInfo($this->name, $originalResolver->toString());
-
-                    throw $e;
-                }
-
-                return $result;
+                return $this->unwrapReturnType($result, $originalResolver);
             };
 
             // GraphQL allows deferring resolving the field's value using promises, i.e. they call the resolve
@@ -98,6 +90,21 @@ public function __construct(
         parent::__construct($config);
     }
 
+    private function unwrapReturnType(mixed $result, ResolverInterface $originalResolver): mixed
+    {
+        if ($result instanceof SyncPromise) {
+            return $result->then(fn ($resolvedValue) => $this->unwrapReturnType($resolvedValue, $originalResolver));
+        }
+        try {
+            $this->assertReturnType($result);
+        } catch (TypeMismatchRuntimeException $e) {
+            $e->addInfo($this->name, $originalResolver->toString());
+
+            throw $e;
+        }
+        return $result;
+    }
+
     /**
      * This method checks the returned value of the resolver to be sure it matches the documented return type.
      * We are sure the returned value is of the correct type... except if the return type is type-hinted as an array.

Diff for: tests/Fixtures/Integration/Models/Blog.php

@@ -4,6 +4,7 @@
 
 namespace TheCodingMachine\GraphQLite\Fixtures\Integration\Models;
 
+use GraphQL\Deferred;
 use TheCodingMachine\GraphQLite\Annotations\Field;
 use TheCodingMachine\GraphQLite\Annotations\Prefetch;
 use TheCodingMachine\GraphQLite\Annotations\Type;
@@ -35,17 +36,13 @@ public function getPosts(
         return $prefetchedPosts[$this->id];
     }
 
-    /**
-     * @param Blog[][] $prefetchedSubBlogs
-     *
-     * @return Blog[]
-     */
-    #[Field]
+    /** @param Blog[][] $prefetchedSubBlogs */
+    #[Field(outputType: '[Blog!]!')]
     public function getSubBlogs(
         #[Prefetch('prefetchSubBlogs')]
         array $prefetchedSubBlogs,
-    ): array {
-        return $prefetchedSubBlogs[$this->id];
+    ): Deferred {
+        return new Deferred(fn () => $prefetchedSubBlogs[$this->id]);
     }
 
     /**