From f3f9d085d10b745d6f15775f145be81db34eb900 Mon Sep 17 00:00:00 2001
From: Robert Dailey <rcdailey@gmail.com>
Date: Sat, 15 May 2021 14:39:23 -0500
Subject: [PATCH] fix: handle invalid cache data

If cache data is invalid, catch the exception and log an error. But the
app should continue and not stop there. Just proceed without cache.
---
 CHANGELOG.md                              |  5 +++++
 src/Trash.Tests/Cache/ServiceCacheTest.cs | 16 +++++++++++++++-
 src/Trash/Cache/ServiceCache.cs           | 19 +++++++++++++++++--
 3 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2548ca53..a56ed23e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Invalid cache data files no longer cause the program to exit. An error is printed and the
+  application continues as if there was no cache at all.
+
 ### Changed
 
 - The log message listing custom formats without scores in the guide now prints information one per
diff --git a/src/Trash.Tests/Cache/ServiceCacheTest.cs b/src/Trash.Tests/Cache/ServiceCacheTest.cs
index b992102e..ec105e91 100644
--- a/src/Trash.Tests/Cache/ServiceCacheTest.cs
+++ b/src/Trash.Tests/Cache/ServiceCacheTest.cs
@@ -5,6 +5,7 @@ using FluentAssertions;
 using Newtonsoft.Json;
 using NSubstitute;
 using NUnit.Framework;
+using Serilog;
 using Trash.Cache;
 using Trash.Config;
 
@@ -21,7 +22,7 @@ namespace Trash.Tests.Cache
                 Filesystem = fs ?? Substitute.For<IFileSystem>();
                 StoragePath = Substitute.For<ICacheStoragePath>();
                 ServiceConfig = Substitute.For<IServiceConfiguration>();
-                Cache = new ServiceCache(Filesystem, StoragePath, ServiceConfig);
+                Cache = new ServiceCache(Filesystem, StoragePath, ServiceConfig, Substitute.For<ILogger>());
             }
 
             public ServiceCache Cache { get; }
@@ -141,5 +142,18 @@ namespace Trash.Tests.Cache
                 .Throw<ArgumentException>()
                 .WithMessage("CacheObjectNameAttribute is missing*");
         }
+
+        [Test]
+        public void When_cache_file_is_empty_do_not_throw()
+        {
+            var ctx = new Context();
+            ctx.Filesystem.File.Exists(Arg.Any<string>()).Returns(true);
+            ctx.Filesystem.File.ReadAllText(Arg.Any<string>())
+                .Returns(_ => "");
+
+            Action act = () => ctx.Cache.Load<ObjectWithAttribute>();
+
+            act.Should().NotThrow();
+        }
     }
 }
diff --git a/src/Trash/Cache/ServiceCache.cs b/src/Trash/Cache/ServiceCache.cs
index bcdaa010..4cd79202 100644
--- a/src/Trash/Cache/ServiceCache.cs
+++ b/src/Trash/Cache/ServiceCache.cs
@@ -7,6 +7,7 @@ using System.Text;
 using System.Text.RegularExpressions;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
+using Serilog;
 using Trash.Config;
 
 namespace Trash.Cache
@@ -19,14 +20,18 @@ namespace Trash.Cache
         private readonly IFNV1a _hash;
         private readonly ICacheStoragePath _storagePath;
 
-        public ServiceCache(IFileSystem fileSystem, ICacheStoragePath storagePath, IServiceConfiguration config)
+        public ServiceCache(IFileSystem fileSystem, ICacheStoragePath storagePath, IServiceConfiguration config,
+            ILogger log)
         {
             _fileSystem = fileSystem;
             _storagePath = storagePath;
             _config = config;
+            Log = log;
             _hash = FNV1aFactory.Instance.Create(FNVConfig.GetPredefinedConfig(32));
         }
 
+        private ILogger Log { get; }
+
         public T? Load<T>() where T : class
         {
             var path = PathFromAttribute<T>();
@@ -36,7 +41,17 @@ namespace Trash.Cache
             }
 
             var json = _fileSystem.File.ReadAllText(path);
-            return JObject.Parse(json).ToObject<T>();
+
+            try
+            {
+                return JObject.Parse(json).ToObject<T>();
+            }
+            catch (JsonException e)
+            {
+                Log.Error("Failed to read cache data, will proceed without cache. Reason: {Msg}", e.Message);
+            }
+
+            return null;
         }
 
         public void Save<T>(T obj) where T : class