Add IDiagnosticContext.SetException()

Author: angularsen

src/Serilog.Extensions.Hosting/Extensions/Hosting/DiagnosticContext.cs

@@ -56,5 +56,12 @@ public void Set(string propertyName, object value, bool destructureObjects = fal
                 collector.AddOrUpdate(property);
             }
         }
+
+        /// <inheritdoc cref="IDiagnosticContext.SetException"/>
+        public void SetException(Exception exception)
+        {
+            var collector = AmbientDiagnosticContextCollector.Current;
+            collector?.SetException(exception);
+        }
     }
 }

src/Serilog.Extensions.Hosting/Extensions/Hosting/DiagnosticContextCollector.cs

@@ -11,6 +11,7 @@ public sealed class DiagnosticContextCollector : IDisposable
     {
         readonly IDisposable _chainedDisposable;
         readonly object _propertiesLock = new object();
+        Exception _exception;
         Dictionary<string, LogEventProperty> _properties = new Dictionary<string, LogEventProperty>();
 
         /// <summary>
@@ -38,6 +39,28 @@ public void AddOrUpdate(LogEventProperty property)
             }
         }
 
+        /// <summary>
+        /// Set an exception to include in the Serilog request log event.
+        /// </summary>
+        /// <example>
+        /// Passing an exception to the diagnostic context is useful when unhandled exceptions are handled before reaching Serilog's
+        /// RequestLoggingMiddleware. One example is using https://www.nuget.org/packages/Hellang.Middleware.ProblemDetails to transform
+        /// exceptions to ProblemDetails responses.
+        /// </example>
+        /// <remarks>
+        /// If an unhandled exception reaches Serilog's RequestLoggingMiddleware, then the unhandled exception takes precedence.<br/>
+        /// If <c>null</c> is given, it clears any previously assigned exception.
+        /// </remarks>
+        /// <param name="exception">The exception to log.</param>
+        public void SetException(Exception exception)
+        {
+            lock (_propertiesLock)
+            {
+                if (_properties == null) return;
+                _exception = exception;
+            }
+        }
+
         /// <summary>
         /// Complete the context and retrieve the properties added to it, if any. This will
         /// stop collection and remove the collector from the original execution context and
@@ -51,6 +74,36 @@ public bool TryComplete(out IEnumerable<LogEventProperty> properties)
             {
                 properties = _properties?.Values;
                 _properties = null;
+                _exception = null;
+                Dispose();
+                return properties != null;
+            }
+        }
+
+        /// <summary>
+        /// Complete the context and retrieve the properties added to it, if any. This will
+        /// stop collection and remove the collector from the original execution context and
+        /// any of its children.
+        /// </summary>
+        /// <param name="properties">The collected properties, or null if no collection is active.</param>
+        /// <param name="exception">The collected exception, or null if none has been collected or if no collection is active.</param>
+        /// <returns>True if properties could be collected.</returns>
+        /// <example>
+        /// This overload provides the exception collected by the diagnostic context, which is useful when unhandled exceptions are handled
+        /// before reaching Serilog's RequestLoggingMiddleware. One example is using https://www.nuget.org/packages/Hellang.Middleware.ProblemDetails to transform
+        /// exceptions to ProblemDetails responses.
+        /// </example>
+        /// <remarks>
+        /// If an unhandled exception reaches Serilog's RequestLoggingMiddleware, then the unhandled exception should take precedence.<br/>
+        /// </remarks>
+        public bool TryComplete(out IEnumerable<LogEventProperty> properties, out Exception exception)
+        {
+            lock (_propertiesLock)
+            {
+                properties = _properties?.Values;
+                exception = _exception;
+                _properties = null;
+                _exception = null;
                 Dispose();
                 return properties != null;
             }

src/Serilog.Extensions.Hosting/IDiagnosticContext.cs

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+using System;
+
 namespace Serilog
 {
     /// <summary>
@@ -27,6 +29,21 @@ public interface IDiagnosticContext
         /// <param name="value">The property value.</param>
         /// <param name="destructureObjects">If true, the value will be serialized as structured
         /// data if possible; if false, the object will be recorded as a scalar or simple array.</param>
-        void Set(string propertyName, object value, bool destructureObjects = false); 
+        void Set(string propertyName, object value, bool destructureObjects = false);
+
+        /// <summary>
+        /// Set an exception to include in the Serilog request log event.
+        /// </summary>
+        /// <example>
+        /// Passing an exception to the diagnostic context is useful when unhandled exceptions are handled before reaching Serilog's
+        /// RequestLoggingMiddleware. One example is using https://www.nuget.org/packages/Hellang.Middleware.ProblemDetails to transform
+        /// exceptions to ProblemDetails responses.
+        /// </example>
+        /// <remarks>
+        /// If an unhandled exception reaches Serilog's RequestLoggingMiddleware, then the unhandled exception takes precedence.<br/>
+        /// If <c>null</c> is given, it clears any previously assigned exception.
+        /// </remarks>
+        /// <param name="exception">The exception to log.</param>
+        void SetException(Exception exception);
     }
 }