Log error messages when the manifest URL is not valid

Emby.Server.Implementations/Updates/InstallationManager.cs

@@ -3,8 +3,10 @@ using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Net;
 using System.Net.Http;
 using System.Runtime.CompilerServices;
+using System.Runtime.Serialization;
 using System.Security.Cryptography;
 using System.Threading;
 using System.Threading.Tasks;
@@ -120,11 +122,15 @@ namespace Emby.Server.Implementations.Updates
 
         /// <inheritdoc />
         public async Task<IReadOnlyList<PackageInfo>> GetAvailablePackages(CancellationToken cancellationToken = default)
+        {
+            var manifestUrl = _appConfig.GetValue<string>(PluginManifestUrlKey);
+
+            try
             {
                 using (var response = await _httpClient.SendAsync(
                     new HttpRequestOptions
                     {
-                    Url = _appConfig.GetValue<string>(PluginManifestUrlKey),
+                        Url = manifestUrl,
                         CancellationToken = cancellationToken,
                         CacheMode = CacheMode.Unconditional,
                         CacheLength = TimeSpan.FromMinutes(3)
@@ -132,8 +138,28 @@ namespace Emby.Server.Implementations.Updates
                     HttpMethod.Get).ConfigureAwait(false))
                 using (Stream stream = response.Content)
                 {
-                return await _jsonSerializer.DeserializeFromStreamAsync<IReadOnlyList<PackageInfo>>(
-                    stream).ConfigureAwait(false);
+                    try
+                    {
+                        return await _jsonSerializer.DeserializeFromStreamAsync<IReadOnlyList<PackageInfo>>(stream).ConfigureAwait(false);
+                    }
+                    catch (SerializationException ex)
+                    {
+                        const string LogTemplate =
+                            "Failed to deserialize the plugin manifest retrieved from {PluginManifestUrl}. If you " +
+                            "have specified a custom plugin repository manifest URL with --plugin-manifest-url or " +
+                            PluginManifestUrlKey + ", please ensure that it is correct.";
+                        _logger.LogError(ex, LogTemplate, manifestUrl);
+                        throw;
+                    }
+                }
+            }
+            catch (UriFormatException ex)
+            {
+                const string LogTemplate =
+                    "The URL configured for the plugin repository manifest URL is not valid: {PluginManifestUrl}. " +
+                    "Please check the URL configured by --plugin-manifest-url or " + PluginManifestUrlKey;
+                _logger.LogError(ex, LogTemplate, manifestUrl);
+                throw;
             }
         }