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;
@@ -121,19 +123,43 @@ namespace Emby.Server.Implementations.Updates
         /// <inheritdoc />
         public async Task<IReadOnlyList<PackageInfo>> GetAvailablePackages(CancellationToken cancellationToken = default)
         {
-            using (var response = await _httpClient.SendAsync(
-                new HttpRequestOptions
+            var manifestUrl = _appConfig.GetValue<string>(PluginManifestUrlKey);
+
+            try
+            {
+                using (var response = await _httpClient.SendAsync(
+                    new HttpRequestOptions
+                    {
+                        Url = manifestUrl,
+                        CancellationToken = cancellationToken,
+                        CacheMode = CacheMode.Unconditional,
+                        CacheLength = TimeSpan.FromMinutes(3)
+                    },
+                    HttpMethod.Get).ConfigureAwait(false))
+                using (Stream stream = response.Content)
                 {
-                    Url = _appConfig.GetValue<string>(PluginManifestUrlKey),
-                    CancellationToken = cancellationToken,
-                    CacheMode = CacheMode.Unconditional,
-                    CacheLength = TimeSpan.FromMinutes(3)
-                },
-                HttpMethod.Get).ConfigureAwait(false))
-            using (Stream stream = response.Content)
+                    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)
             {
-                return await _jsonSerializer.DeserializeFromStreamAsync<IReadOnlyList<PackageInfo>>(
-                    stream).ConfigureAwait(false);
+                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;
             }
         }