From 9fe2ba3039ccc74f92317fe952f59221d75564e1 Mon Sep 17 00:00:00 2001
From: James Turner <Turnerj@users.noreply.github.com>
Date: Thu, 21 Sep 2023 22:47:50 +0930
Subject: [PATCH] Fix file manifest null reference exception (#265)

The cache manifest can deserialize as `null` under certain circumstances. In those cases, we need to initialise the cache manifest as if this is a fresh file.
---
 src/CacheTower/Providers/FileSystem/FileCacheLayer.cs        | 3 ++-
 src/CacheTower/Providers/FileSystem/FileCacheLayerOptions.cs | 4 ++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/CacheTower/Providers/FileSystem/FileCacheLayer.cs b/src/CacheTower/Providers/FileSystem/FileCacheLayer.cs
index 65ef50c7..f98ae9af 100644
--- a/src/CacheTower/Providers/FileSystem/FileCacheLayer.cs
+++ b/src/CacheTower/Providers/FileSystem/FileCacheLayer.cs
@@ -89,6 +89,7 @@ private async Task TryLoadManifestAsync()
 						if (File.Exists(ManifestPath))
 						{
 							CacheManifest = await DeserializeFileAsync<ConcurrentDictionary<string?, ManifestEntry>>(ManifestPath);
+							CacheManifest ??= new();
 						}
 						else
 						{
@@ -97,7 +98,7 @@ private async Task TryLoadManifestAsync()
 								Directory.CreateDirectory(Options.DirectoryPath);
 							}
 
-							CacheManifest = new ConcurrentDictionary<string?, ManifestEntry>();
+							CacheManifest = new();
 							await SerializeFileAsync(ManifestPath, CacheManifest);
 						}
 					}
diff --git a/src/CacheTower/Providers/FileSystem/FileCacheLayerOptions.cs b/src/CacheTower/Providers/FileSystem/FileCacheLayerOptions.cs
index fcde2bdc..e0f25f24 100644
--- a/src/CacheTower/Providers/FileSystem/FileCacheLayerOptions.cs
+++ b/src/CacheTower/Providers/FileSystem/FileCacheLayerOptions.cs
@@ -13,9 +13,9 @@ ICacheSerializer Serializer
 )
 {
 	/// <summary>
-	/// The default manifest save interval of 5 minutes.
+	/// The default manifest save interval of 30 seconds.
 	/// </summary>
-	public static readonly TimeSpan DefaultManifestSaveInterval = TimeSpan.FromMinutes(5);
+	public static readonly TimeSpan DefaultManifestSaveInterval = TimeSpan.FromSeconds(30);
 
 	/// <summary>
 	/// The time interval controlling how often the cache manifest is saved to disk.