ExceptionLayoutRenderer - Added FlattenException option (#4153)

snakefoot · web-flow · commit 670c298d72f3 · 2020-11-05T17:06:37.000+01:00
diff --git a/src/NLog/LayoutRenderers/ExceptionLayoutRenderer.cs b/src/NLog/LayoutRenderers/ExceptionLayoutRenderer.cs
@@ -179,8 +179,21 @@ public string InnerFormat
         /// <summary>
         /// Gets or sets whether to render innermost Exception from <see cref="Exception.GetBaseException()"/>
         /// </summary>
+        [DefaultValue(false)]
         public bool BaseException { get; set; }
 
+#if !NET3_5 && !SILVERLIGHT4
+        /// <summary>
+        /// Gets or sets whether to collapse exception tree using <see cref="AggregateException.Flatten()"/>
+        /// </summary>
+#else
+        /// <summary>
+        /// Gets or sets whether to collapse exception tree using AggregateException.Flatten()
+        /// </summary>
+#endif
+        [DefaultValue(true)]
+        public bool FlattenException { get; set; } = true;
+
         /// <summary>
         ///  Gets the formats of the output of inner exceptions to be rendered in target.
         /// </summary>
@@ -226,7 +239,7 @@ protected override void Append(StringBuilder builder, LogEventInfo logEvent)
 #if !NET3_5 && !SILVERLIGHT4
                 if (logEvent.Exception is AggregateException aggregateException)
                 {
-                    primaryException = GetPrimaryException(aggregateException);
+                    primaryException = FlattenException ? GetPrimaryException(aggregateException) : aggregateException;
                     AppendException(primaryException, Formats, builder, aggregateException);
                     if (currentLevel < MaxInnerExceptionLevel)
                     {
@@ -437,15 +450,17 @@ protected virtual void AppendHResult(StringBuilder sb, Exception ex)
             }
 #endif
         }
+
         private void AppendData(StringBuilder builder, Exception ex, Exception aggregateException)
         {
-            if (aggregateException?.Data?.Count > 0)
+            if (aggregateException?.Data?.Count > 0 && !ReferenceEquals(ex, aggregateException))
             {
                 AppendData(builder, aggregateException);
                 builder.Append(Separator);
             }
             AppendData(builder, ex);
         }
+
         /// <summary>
         /// Appends the contents of an Exception's Data property to the specified <see cref="StringBuilder" />.
         /// </summary>
diff --git a/tests/NLog.UnitTests/LayoutRenderers/ExceptionTests.cs b/tests/NLog.UnitTests/LayoutRenderers/ExceptionTests.cs
@@ -783,6 +783,7 @@ public void AggregateExceptionWithExceptionDataSingleTest()
             Assert.Contains(string.Format(ExceptionDataFormat, exceptionDataKey, exceptionDataValue), lastMessage);
             Assert.Contains(string.Format(ExceptionDataFormat, aggregateExceptionDataKey, aggregateExceptionDataValue), lastMessage);
         }
+
         [Fact]
         public void CustomExceptionProperties_Layout_Test()
         {
@@ -819,6 +820,40 @@ public void BaseExceptionTest()
             AssertDebugLastMessage("debug1", "Goodbye World");
         }
 
+#if NET3_5
+        [Fact(Skip = "NET3_5 not supporting AggregateException")]
+#else
+        [Fact]
+#endif
+        public void RecursiveAsyncExceptionWithoutFlattenException()
+        {
+            var recursionCount = 3;
+            Func<int> innerAction = () => throw new ApplicationException("Life is hard");
+            var t1 = System.Threading.Tasks.Task<int>.Factory.StartNew(() =>
+            {
+                return NestedFunc(recursionCount, innerAction);
+            });
+
+            try
+            {
+                t1.Wait();
+            }
+            catch (AggregateException ex)
+            {
+                var layoutRenderer = new ExceptionLayoutRenderer() { Format = "ToString", FlattenException = false };
+                var logEvent = LogEventInfo.Create(LogLevel.Error, null, null, (object)ex);
+                var result = layoutRenderer.Render(logEvent);
+                int needleCount = 0;
+                int foundIndex = result.IndexOf(nameof(NestedFunc), 0);
+                while (foundIndex >= 0)
+                {
+                    ++needleCount;
+                    foundIndex = result.IndexOf(nameof(NestedFunc), foundIndex + nameof(NestedFunc).Length);
+                }
+                Assert.True(needleCount >= recursionCount, $"{needleCount} too small");
+            }
+        }
+
         private class ExceptionWithBrokenMessagePropertyException : NLogConfigurationException
         {
             public override string Message => throw new Exception("Exception from Message property");
@@ -885,6 +920,21 @@ private Exception GetNestedExceptionWithStackTrace(string exceptionMessage)
             }
         }
 
+        private int NestedFunc(int recursion, Func<int> innerAction)
+        {
+            try
+            {
+                if (recursion-- == 0)
+                    return System.Threading.Tasks.Task<int>.Factory.StartNew(() => innerAction.Invoke())
+                        .Result;
+                return NestedFunc(recursion, innerAction);
+            }
+            catch
+            {
+                throw;  // Just to make the method complex, and avoid inline
+            }
+        }
+
         private Exception GetExceptionWithoutStackTrace(string exceptionMessage)
         {
             return new CustomArgumentException(exceptionMessage, "exceptionMessage");
