FIX: modified GetLevel to accept both HttpContext and Exception. This is useful when an exception is thrown but HttpStatusCode is not yet set to 500 InternalServerError

FIX: DefaultGetLevel now returns Error if there is an exception OR if StatusCode > 499

Author: Sebastien Roche

src/Serilog.AspNetCore/AspNetCore/RequestLoggingMiddleware.cs

@@ -29,7 +29,7 @@ class RequestLoggingMiddleware
         readonly RequestDelegate _next;
         readonly DiagnosticContext _diagnosticContext;
         readonly MessageTemplate _messageTemplate;
-        readonly Func<HttpContext, LogEventLevel> _getLevel;
+        readonly Func<HttpContext, Exception, LogEventLevel> _getLevel;
         static readonly LogEventProperty[] NoProperties = new LogEventProperty[0];
 
         public RequestLoggingMiddleware(RequestDelegate next, DiagnosticContext diagnosticContext, RequestLoggingOptions options)
@@ -72,7 +72,7 @@ public async Task Invoke(HttpContext httpContext)
         bool LogCompletion(HttpContext httpContext, DiagnosticContextCollector collector, int statusCode, double elapsedMs, Exception ex)
         {
             var logger = Log.ForContext<RequestLoggingMiddleware>();
-            var level = _getLevel(httpContext);
+            var level = _getLevel(httpContext, ex);
 
             if (!logger.IsEnabled(level)) return false;
 
@@ -98,7 +98,7 @@ static double GetElapsedMilliseconds(long start, long stop)
         {
             return (stop - start) * 1000 / (double)Stopwatch.Frequency;
         }
-        
+
         static string GetPath(HttpContext httpContext)
         {
             return httpContext.Features.Get<IHttpRequestFeature>()?.RawTarget ?? httpContext.Request.Path.ToString();

src/Serilog.AspNetCore/AspNetCore/RequestLoggingOptions.cs

@@ -35,13 +35,13 @@ public class RequestLoggingOptions
         public string MessageTemplate { get; set; }
 
         /// <summary>
-        /// Gets or sets the function returning the <see cref="LogEventLevel"/> based on the current <see cref="HttpContext"/>.
-        /// The default behavior returns LogEventLevel.Error when HttpStatusCode is greater than 499
+        /// Gets or sets the function returning the <see cref="LogEventLevel"/> based on the <see cref="HttpContext"/> and on the <see cref="Exception" /> if something wrong happend 
+        /// The default behavior returns LogEventLevel.Error when HttpStatusCode is greater than 499 or if Exception is not null.
         /// </summary>
         /// <value>
         /// The function returning the <see cref="LogEventLevel"/>.
         /// </value>
-        public Func<HttpContext, LogEventLevel> GetLevel { get; set; }
+        public Func<HttpContext, Exception, LogEventLevel> GetLevel { get; set; }
 
         internal RequestLoggingOptions() { }
     }

src/Serilog.AspNetCore/SerilogApplicationBuilderExtensions.cs

@@ -28,8 +28,12 @@ public static class SerilogApplicationBuilderExtensions
         const string DefaultRequestCompletionMessageTemplate =
             "HTTP {RequestMethod} {RequestPath} responded {StatusCode} in {Elapsed:0.0000} ms";
 
-        static Func<HttpContext, LogEventLevel> DefaultGetLevel = 
-            ctx => ctx.Response.StatusCode > 499 ? LogEventLevel.Error : LogEventLevel.Information;
+        static Func<HttpContext, Exception, LogEventLevel> DefaultGetLevel =
+            (ctx, ex) => ex != null
+                ? LogEventLevel.Error 
+                : ctx.Response.StatusCode > 499 
+                    ? LogEventLevel.Error 
+                    : LogEventLevel.Information;
 
         /// <summary>
         /// Adds middleware for streamlined request logging. Instead of writing HTTP request information