feat: enforce non-nullable payloads in logging interfaces

src/ILogMessage.cs

@@ -8,6 +8,7 @@ namespace WB.Logging;
 /// A log message.
 /// </summary>
 public interface ILogMessage<out TPayload>
+    where TPayload : notnull
 {
     // ┌─────────────────────────────────────────────────────────────────────────────┐
     // │ Public Properties                                                           │
@@ -31,5 +32,5 @@ public interface ILogMessage<out TPayload>
     /// <summary>
     /// Gets the payload of the log message.
     /// </summary>
-    public TPayload? Payload { get; }
+    public TPayload Payload { get; }
 }

src/ILogger.cs

@@ -51,7 +51,8 @@ public interface ILogger : IAsyncDisposable
     /// </summary>
     /// <param name="logLevel">The <see cref="LogLevel"/>.</param>
     /// <param name="payload">The payload to log.</param>
-    public void Log<TPayload>(LogLevel? logLevel, TPayload payload);
+    public void Log<TPayload>(LogLevel? logLevel, TPayload payload)
+        where TPayload : notnull;
 
     /// <summary>
     /// Flushes all pending log messages.

src/ILoggerExtensions.cs

@@ -30,6 +30,7 @@ public void Exception(Exception exception)
         /// <param name="payload">The payload to log.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Info<TPayload>(TPayload payload)
+            where TPayload : notnull
             => @this.Log(LogLevel.Info, payload);
 
         /// <summary>
@@ -38,6 +39,7 @@ public void Info<TPayload>(TPayload payload)
         /// <param name="payload">The payload to log.</param>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Warning<TPayload>(TPayload payload)
+            where TPayload : notnull
             => @this.Log(LogLevel.Warning, payload);
 
         /// <summary>
@@ -47,6 +49,7 @@ public void Warning<TPayload>(TPayload payload)
         [System.Diagnostics.CodeAnalysis.SuppressMessage("Naming", "CA1716:Identifiers should not match keywords", Justification = "Common logging term.")]
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Error<TPayload>(TPayload payload)
+            where TPayload : notnull
             => @this.Log(LogLevel.Error, payload);
     }
 }

src/LogSinks/IAsyncLogSink.cs

@@ -17,5 +17,6 @@ public interface IAsyncLogSink
     /// <param name="logMessage">The <see cref="ILogMessage{TPayload}"/> to submit.</param>
     /// <typeparam name="TPayload">The type of the payload of the log message.</typeparam>
     /// <returns>A <see cref="ValueTask"/> that represents the asynchronous operation of submitting the log message.</returns>
-    public ValueTask SubmitAsync<TPayload>(ILogMessage<TPayload> logMessage);
+    public ValueTask SubmitAsync<TPayload>(ILogMessage<TPayload> logMessage)
+        where TPayload : notnull;
 }

src/LogSinks/ILogSink.cs

@@ -14,5 +14,6 @@ public interface ILogSink
     /// </summary>
     /// <param name="logMessage">The <see cref="ILogMessage{TPayload}"/> to submit.</param>
     /// <typeparam name="TPayload">The type of the payload of the log message.</typeparam>
-    public void Submit<TPayload>(ILogMessage<TPayload> logMessage);
+    public void Submit<TPayload>(ILogMessage<TPayload> logMessage)
+        where TPayload : notnull;
 }

src/LogSinks/ILogSink{TPayload}.cs

@@ -6,6 +6,7 @@ namespace WB.Logging;
 /// </summary>
 /// <typeparam name="TPayload">The type of the payload of the log messages that this log sink can process.</typeparam>
 public interface ILogSink<TPayload>
+    where TPayload : notnull
 {
     // ┌─────────────────────────────────────────────────────────────────────────────┐
     // │ Public Methods                                                              │