Feature: Add ILogger

samples/01_basic_ping_bot/Program.cs

@@ -31,8 +31,7 @@ public Program()
             // It is recommended to Dispose of a client when you are finished
             // using it, at the end of your app's lifetime.
             _client = new DiscordSocketClient();
-
-            _client.Log += LogAsync;
+
             _client.Ready += ReadyAsync;
             _client.MessageReceived += MessageReceivedAsync;
         }
@@ -47,12 +46,6 @@ public async Task MainAsync()
             await Task.Delay(Timeout.Infinite);
         }
 
-        private Task LogAsync(LogMessage log)
-        {
-            Console.WriteLine(log.ToString());
-            return Task.CompletedTask;
-        }
-
         // The Ready event indicates that the client has opened a
         // connection and it is now safe to access the cache.
         private Task ReadyAsync()

samples/02_commands_framework/Program.cs

@@ -35,9 +35,6 @@ public async Task MainAsync()
             {
                 var client = services.GetRequiredService<DiscordSocketClient>();
 
-                client.Log += LogAsync;
-                services.GetRequiredService<CommandService>().Log += LogAsync;
-
                 // Tokens should be considered secret data and never hard-coded.
                 // We can read from the environment variable to avoid hardcoding.
                 await client.LoginAsync(TokenType.Bot, Environment.GetEnvironmentVariable("token"));
@@ -50,13 +47,6 @@ public async Task MainAsync()
             }
         }
 
-        private Task LogAsync(LogMessage log)
-        {
-            Console.WriteLine(log.ToString());
-
-            return Task.CompletedTask;
-        }
-
         private ServiceProvider ConfigureServices()
         {
             return new ServiceCollection()

samples/03_sharded_client/Program.cs

@@ -38,7 +38,6 @@ public async Task MainAsync()
                 // The ShardReady event is used instead, allowing for individual
                 // control per shard.
                 client.ShardReady += ReadyAsync;
-                client.Log += LogAsync;
 
                 await services.GetRequiredService<CommandHandlingService>().InitializeAsync();
 
@@ -65,11 +64,5 @@ private Task ReadyAsync(DiscordSocketClient shard)
             Console.WriteLine($"Shard Number {shard.ShardId} is connected and ready!");
             return Task.CompletedTask;
         }
-
-        private Task LogAsync(LogMessage log)
-        {
-            Console.WriteLine(log.ToString());
-            return Task.CompletedTask;
-        }
     }
 }

samples/03_sharded_client/Services/CommandHandlingService.cs

@@ -21,7 +21,6 @@ public CommandHandlingService(IServiceProvider services)
             _services = services;
 
             _commands.CommandExecuted += CommandExecutedAsync;
-            _commands.Log += LogAsync;
             _discord.MessageReceived += MessageReceivedAsync;
         }
 
@@ -61,12 +60,5 @@ public async Task CommandExecutedAsync(Optional<CommandInfo> command, ICommandCo
             // the command failed, let's notify the user that something happened.
             await context.Channel.SendMessageAsync($"error: {result.ToString()}");
         }
-
-        private Task LogAsync(LogMessage log)
-        {
-            Console.WriteLine(log.ToString());
-
-            return Task.CompletedTask;
-        }
     }
 }

samples/idn/Program.cs

@@ -34,60 +34,15 @@ public class Program
         static async Task Main(string[] args)
         {
             var token = File.ReadAllText("token.ignore");
-            var client = new DiscordSocketClient(new DiscordSocketConfig { LogLevel = LogSeverity.Debug });
-            var logQueue = new ConcurrentQueue<LogMessage>();
+            var client = new DiscordSocketClient(new DiscordSocketConfig { });
             var logCancelToken = new CancellationTokenSource();
             int presenceUpdates = 0;
-
-            client.Log += msg =>
-            {
-                logQueue.Enqueue(msg);
-                return Task.CompletedTask;
-            };
+
             Console.CancelKeyPress += (_ev, _s) =>
             {
                 logCancelToken.Cancel();
             };
 
-            var logTask = Task.Run(async () =>
-            {
-                var fs = new FileStream("idn.log", FileMode.Append);
-                var logStringBuilder = new StringBuilder(200);
-                string logString = "";
-
-                byte[] helloBytes = Encoding.UTF8.GetBytes($"### new log session: {DateTime.Now} ###\n\n");
-                await fs.WriteAsync(helloBytes);
-
-                while (!logCancelToken.IsCancellationRequested)
-                {
-                    if (logQueue.TryDequeue(out var msg))
-                    {
-                        if (msg.Message?.IndexOf("PRESENCE_UPDATE)") > 0)
-                        {
-                            presenceUpdates++;
-                            continue;
-                        }
-
-                        _ = msg.ToString(builder: logStringBuilder);
-                        logStringBuilder.AppendLine();
-                        logString = logStringBuilder.ToString();
-
-                        Debug.Write(logString, "DNET");
-                        await fs.WriteAsync(Encoding.UTF8.GetBytes(logString));
-                    }
-                    await fs.FlushAsync();
-                    try
-                    {
-                        await Task.Delay(100, logCancelToken.Token);
-                    }
-                    finally { }
-                }
-
-                byte[] goodbyeBytes = Encoding.UTF8.GetBytes($"#!! end log session: {DateTime.Now} !!#\n\n\n");
-                await fs.WriteAsync(goodbyeBytes);
-                await fs.DisposeAsync();
-            });
-
             await client.LoginAsync(TokenType.Bot, token);
             await client.StartAsync();
 
@@ -127,9 +82,9 @@ static async Task Main(string[] args)
             await client.StopAsync();
             client.Dispose();
             logCancelToken.Cancel();
-            try
-            { await logTask; }
-            finally { Console.WriteLine("goodbye!"); }
+
+            await Task.Delay(-1, logCancelToken.Token);
+            Console.WriteLine("goodbye!");
         }
 
         static IEnumerable<Assembly> GetAssemblies()

src/Discord.Net.Commands/Builders/ModuleClassBuilder.cs

@@ -5,6 +5,7 @@
 using System.Threading.Tasks;
 
 using Discord.Commands.Builders;
+using Microsoft.Extensions.Logging;
 
 namespace Discord.Commands
 {
@@ -34,7 +35,7 @@ bool IsLoadableModule(TypeInfo info)
                 }
                 else if (IsLoadableModule(typeInfo))
                 {
-                    await service._cmdLogger.WarningAsync($"Class {typeInfo.FullName} is not public and cannot be loaded. To suppress this message, mark the class with {nameof(DontAutoLoadAttribute)}.").ConfigureAwait(false);
+                    service._cmdLogger.LogWarning($"Class {typeInfo.FullName} is not public and cannot be loaded. To suppress this message, mark the class with {nameof(DontAutoLoadAttribute)}.");
                 }
             }
 
@@ -69,7 +70,7 @@ public static async Task<Dictionary<Type, ModuleInfo>> BuildAsync(IEnumerable<Ty
                 result[typeInfo.AsType()] = module.Build(service, services);
             }
 
-            await service._cmdLogger.DebugAsync($"Successfully built {builtTypes.Count} modules.").ConfigureAwait(false);
+            service._cmdLogger.LogDebug($"Successfully built {builtTypes.Count} modules.");
 
             return result;
         }

src/Discord.Net.Commands/CommandService.cs

@@ -8,6 +8,7 @@
 using System.Threading.Tasks;
 using Discord.Commands.Builders;
 using Discord.Logging;
+using Microsoft.Extensions.Logging;
 
 namespace Discord.Commands
 {
@@ -29,12 +30,6 @@ namespace Discord.Commands
     /// </remarks>
     public class CommandService : IDisposable
     {
-        /// <summary>
-        ///     Occurs when a command-related information is received.
-        /// </summary>
-        public event Func<LogMessage, Task> Log { add { _logEvent.Add(value); } remove { _logEvent.Remove(value); } }
-        internal readonly AsyncEvent<Func<LogMessage, Task>> _logEvent = new AsyncEvent<Func<LogMessage, Task>>();
-
         /// <summary>
         ///     Occurs when a command is executed.
         /// </summary>
@@ -56,8 +51,8 @@ public class CommandService : IDisposable
         internal readonly bool _caseSensitive, _throwOnError, _ignoreExtraArgs;
         internal readonly char _separatorChar;
         internal readonly RunMode _defaultRunMode;
-        internal readonly Logger _cmdLogger;
-        internal readonly LogManager _logManager;
+        internal readonly ILogger _cmdLogger;
+        internal readonly ILoggerFactory _logManager;
         internal readonly IReadOnlyDictionary<char, char> _quotationMarkAliasMap;
 
         internal bool _isDisposed;
@@ -100,8 +95,14 @@ public CommandService(CommandServiceConfig config)
             if (_defaultRunMode == RunMode.Default)
                 throw new InvalidOperationException("The default run mode cannot be set to Default.");
 
-            _logManager = new LogManager(config.LogLevel);
-            _logManager.Message += async msg => await _logEvent.InvokeAsync(msg).ConfigureAwait(false);
+            _logManager = config.LoggerFactory;
+
+            if (_logManager == null)
+            {
+                _logManager = new DefaultLoggerFactory();
+                _logManager.AddProvider(new DefaultLoggerProvider());
+            }
+
             _cmdLogger = _logManager.CreateLogger("Command");
 
             _moduleLock = new SemaphoreSlim(1, 1);
@@ -349,7 +350,8 @@ public void AddTypeReader<T>(TypeReader reader)
         public void AddTypeReader(Type type, TypeReader reader)
         {
             if (_defaultTypeReaders.ContainsKey(type))
-                _ = _cmdLogger.WarningAsync($"The default TypeReader for {type.FullName} was replaced by {reader.GetType().FullName}." +
+                _cmdLogger.LogWarning(
+                    $"The default TypeReader for {type.FullName} was replaced by {reader.GetType().FullName}." +
                     "To suppress this message, use AddTypeReader<T>(reader, true).");
             AddTypeReader(type, reader, true);
         }

src/Discord.Net.Commands/CommandServiceConfig.cs

@@ -1,3 +1,4 @@
+using Microsoft.Extensions.Logging;
 using System.Collections.Generic;
 
 namespace Discord.Commands
@@ -23,10 +24,7 @@ public class CommandServiceConfig
         /// </summary>
         public bool CaseSensitiveCommands { get; set; } = false;
 
-        /// <summary>
-        ///     Gets or sets the minimum log level severity that will be sent to the <see cref="CommandService.Log"/> event.
-        /// </summary>
-        public LogSeverity LogLevel { get; set; } = LogSeverity.Info;
+        public ILoggerFactory LoggerFactory { get; set; }
 
         /// <summary>
         ///     Gets or sets whether <see cref="RunMode.Sync"/> commands should push exceptions up to the caller.

src/Discord.Net.Commands/Info/CommandInfo.cs

@@ -1,4 +1,5 @@
 using Discord.Commands.Builders;
+using Microsoft.Extensions.Logging;
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -240,7 +241,7 @@ public async Task<IResult> ExecuteAsync(ICommandContext context, IEnumerable<obj
 
         private async Task<IResult> ExecuteInternalAsync(ICommandContext context, object[] args, IServiceProvider services)
         {
-            await Module.Service._cmdLogger.DebugAsync($"Executing {GetLogText(context)}").ConfigureAwait(false);
+            Module.Service._cmdLogger.LogDebug($"Executing {GetLogText(context)}");
             try
             {
                 var task = _action(context, args, services, this);
@@ -274,7 +275,7 @@ private async Task<IResult> ExecuteInternalAsync(ICommandContext context, object
                     ex = ex.InnerException;
 
                 var wrappedEx = new CommandException(this, context, ex);
-                await Module.Service._cmdLogger.ErrorAsync(wrappedEx).ConfigureAwait(false);
+                Module.Service._cmdLogger.LogError(wrappedEx, wrappedEx.Message);
 
                 var result = ExecuteResult.FromError(ex);
                 await Module.Service._commandExecutedEvent.InvokeAsync(this, context, result).ConfigureAwait(false);
@@ -291,7 +292,7 @@ private async Task<IResult> ExecuteInternalAsync(ICommandContext context, object
             }
             finally
             {
-                await Module.Service._cmdLogger.VerboseAsync($"Executed {GetLogText(context)}").ConfigureAwait(false);
+                Module.Service._cmdLogger.LogTrace($"Executed {GetLogText(context)}");
             }
         }
 

src/Discord.Net.Core/Discord.Net.Core.csproj

@@ -9,6 +9,7 @@
     <TargetFrameworks Condition=" '$(OS)' != 'Windows_NT' ">netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="5.0.0" />
     <PackageReference Include="Newtonsoft.Json" Version="12.0.2" />
     <PackageReference Include="System.Collections.Immutable" Version="1.3.1" />
     <PackageReference Include="System.Interactive.Async" Version="4.0.0" />

src/Discord.Net.Core/DiscordConfig.cs

@@ -1,3 +1,4 @@
+using Microsoft.Extensions.Logging;
 using System.Reflection;
 
 namespace Discord
@@ -123,14 +124,8 @@ public class DiscordConfig
         ///     The currently set <see cref="RetryMode"/>.
         /// </returns>
         public RetryMode DefaultRetryMode { get; set; } = RetryMode.AlwaysRetry;
-
-        /// <summary>
-        ///     Gets or sets the minimum log level severity that will be sent to the Log event.
-        /// </summary>
-        /// <returns>
-        ///     The currently set <see cref="LogSeverity"/> for logging level.
-        /// </returns>
-        public LogSeverity LogLevel { get; set; } = LogSeverity.Info;
+
+        public ILoggerFactory LoggerFactory { get; set; }
 
         /// <summary>
         ///     Gets or sets whether the initial log entry should be printed.

src/Discord.Net.Core/Logging/DefaultLogger.cs

@@ -0,0 +1,52 @@
+using Microsoft.Extensions.Logging;
+using System;
+
+namespace Discord.Logging
+{
+    internal class DefaultLogger : ILogger
+    {
+        private static readonly object _lock = new object();
+
+        private LogLevel MinimumLevel { get; }
+
+        internal DefaultLogger(LogLevel minLevel = LogLevel.Information)
+        {
+            this.MinimumLevel = minLevel;
+        }
+
+        public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception exception, Func<TState, Exception, string> formatter)
+        {
+            if (!this.IsEnabled(logLevel))
+                return;
+
+            lock (_lock)
+            {
+                Console.Write($"{DateTime.Now} ");
+
+                Console.Write(logLevel switch 
+                {
+                    LogLevel.Trace =>       "[Trace] ",
+                    LogLevel.Debug =>       "[Debug] ",
+                    LogLevel.Information => "[Info ] ",
+                    LogLevel.Warning =>     "[Warn ] ",
+                    LogLevel.Error =>       "[Error] ",
+                    LogLevel.Critical =>    "[Crit ] ",
+                    LogLevel.None =>        "[None ] ",
+                    _ =>                    "[?????] "
+                });
+
+                var message = formatter(state, exception);
+                Console.WriteLine(message);
+                if (exception != null)
+                    Console.WriteLine(exception);
+            }
+        }
+
+        public bool IsEnabled(LogLevel logLevel) => logLevel >= this.MinimumLevel;
+
+        public IDisposable BeginScope<TState>(TState state)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}