From 3fc447e50d6808b6c48dba0d01371e37a361b7ee Mon Sep 17 00:00:00 2001
From: Koen Punt <koen@koenpunt.nl>
Date: Thu, 30 Dec 2021 12:20:21 +0100
Subject: [PATCH] Allow null values to async handler methods

Previously when the argument contained a null value (for example for nullified
continuation when using a suspend fun), it would fail to convert the arguments,
because of a `NullPointerException`.

By allowing the mono value be nullable it converts the arguments successfully.

Closes gh-239
---
 .../graphql/data/method/InvocableHandlerMethodSupport.java      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/spring-graphql/src/main/java/org/springframework/graphql/data/method/InvocableHandlerMethodSupport.java b/spring-graphql/src/main/java/org/springframework/graphql/data/method/InvocableHandlerMethodSupport.java
index 58991fa0..bb0f86a3 100644
--- a/spring-graphql/src/main/java/org/springframework/graphql/data/method/InvocableHandlerMethodSupport.java
+++ b/spring-graphql/src/main/java/org/springframework/graphql/data/method/InvocableHandlerMethodSupport.java
@@ -96,7 +96,7 @@ public abstract class InvocableHandlerMethodSupport extends HandlerMethod {
 
 		List<Mono<Object>> monoList = Arrays.stream(args)
 				.map(arg -> {
-					Mono<Object> argMono = (arg instanceof Mono ? (Mono<Object>) arg : Mono.just(arg));
+					Mono<Object> argMono = (arg instanceof Mono ? (Mono<Object>) arg : Mono.justOrEmpty(arg));
 					return argMono.defaultIfEmpty(NO_VALUE);
 				})
 				.collect(Collectors.toList());