From 1b767fb744d5a058dbebc1b7b0e7bc16363ee3d4 Mon Sep 17 00:00:00 2001
From: Chris Povirk <cpovirk@google.com>
Date: Tue, 3 Dec 2024 14:12:04 -0500
Subject: [PATCH] Allow async loads to return `null`.

This makes them match what `CacheLoader` already allows for synchronous
loading and reloading via `@Nullable V load(K key)` and `@Nullable V
reload(K key, V oldValue)`.
---
 .../com/github/benmanes/caffeine/cache/AsyncCacheLoader.java | 5 +++--
 .../java/com/github/benmanes/caffeine/cache/CacheLoader.java | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/caffeine/src/main/java/com/github/benmanes/caffeine/cache/AsyncCacheLoader.java b/caffeine/src/main/java/com/github/benmanes/caffeine/cache/AsyncCacheLoader.java
index 745922807a..8abff8d7e1 100644
--- a/caffeine/src/main/java/com/github/benmanes/caffeine/cache/AsyncCacheLoader.java
+++ b/caffeine/src/main/java/com/github/benmanes/caffeine/cache/AsyncCacheLoader.java
@@ -25,6 +25,7 @@
 import java.util.function.Function;
 
 import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
 
 /**
  * Computes or retrieves values asynchronously based on a key, for use in populating a
@@ -62,7 +63,7 @@ public interface AsyncCacheLoader<K, V> {
    *         treated like any other {@code Exception} in all respects except that, when it is
    *         caught, the thread's interrupt status is set
    */
-  CompletableFuture<? extends V> asyncLoad(K key, Executor executor) throws Exception;
+  CompletableFuture<? extends @Nullable V> asyncLoad(K key, Executor executor) throws Exception;
 
   /**
    * Asynchronously computes or retrieves the values corresponding to {@code keys}. This method is
@@ -114,7 +115,7 @@ public interface AsyncCacheLoader<K, V> {
    *         treated like any other {@code Exception} in all respects except that, when it is
    *         caught, the thread's interrupt status is set
    */
-  default CompletableFuture<? extends V> asyncReload(
+  default CompletableFuture<? extends @Nullable V> asyncReload(
       K key, V oldValue, Executor executor) throws Exception {
     return asyncLoad(key, executor);
   }
diff --git a/caffeine/src/main/java/com/github/benmanes/caffeine/cache/CacheLoader.java b/caffeine/src/main/java/com/github/benmanes/caffeine/cache/CacheLoader.java
index 217c81a868..3d8b9ca642 100644
--- a/caffeine/src/main/java/com/github/benmanes/caffeine/cache/CacheLoader.java
+++ b/caffeine/src/main/java/com/github/benmanes/caffeine/cache/CacheLoader.java
@@ -101,7 +101,7 @@ public interface CacheLoader<K, V> extends AsyncCacheLoader<K, V> {
    * @return the future value associated with {@code key}
    */
   @Override
-  default CompletableFuture<? extends V> asyncLoad(K key, Executor executor) throws Exception {
+  default CompletableFuture<? extends @Nullable V> asyncLoad(K key, Executor executor) throws Exception {
     requireNonNull(key);
     requireNonNull(executor);
     return CompletableFuture.supplyAsync(() -> {
@@ -193,7 +193,7 @@ default CompletableFuture<? extends V> asyncLoad(K key, Executor executor) throw
    *         {@code null} if the mapping is to be removed
    */
   @Override
-  default CompletableFuture<? extends V> asyncReload(
+  default CompletableFuture<? extends @Nullable V> asyncReload(
       K key, V oldValue, Executor executor) throws Exception {
     requireNonNull(key);
     requireNonNull(executor);