adding exception details to FileLogger

Author: brettsam

src/WebJobs.Script/Diagnostics/FileLogger.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.Text;
+using Microsoft.Azure.WebJobs.Host;
 using Microsoft.Extensions.Logging;
 
 namespace Microsoft.Azure.WebJobs.Script.Diagnostics
@@ -62,6 +63,28 @@ public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Except
                 return;
             }
 
+            if (exception != null)
+            {
+                if (exception is FunctionInvocationException ||
+                    exception is AggregateException)
+                {
+                    // we want to minimize the stack traces for function invocation
+                    // failures, so we drill into the very inner exception, which will
+                    // be the script error
+                    Exception actualException = exception;
+                    while (actualException.InnerException != null)
+                    {
+                        actualException = actualException.InnerException;
+                    }
+
+                    formattedMessage += $"{Environment.NewLine}{actualException.Message}";
+                }
+                else
+                {
+                    formattedMessage += $"{Environment.NewLine}{exception.ToFormattedString()}";
+                }
+            }
+
             formattedMessage = FormatLine(stateValues, logLevel, formattedMessage);
             _fileWriter.AppendLine(formattedMessage);
 

test/WebJobs.Script.Tests/Diagnostics/FileLoggerTests.cs

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using Microsoft.Azure.WebJobs.Host;
 using Microsoft.Azure.WebJobs.Logging;
 using Microsoft.Azure.WebJobs.Script.Diagnostics;
 using Microsoft.Extensions.Logging;
@@ -157,6 +158,62 @@ public void FileLogger_LogsExpectedLines()
                 t => Assert.EndsWith("[Information,TestFunction] Test Message With Function", t));
         }
 
+        [Fact]
+        public void FileLogger_LogsFunctionInvocationException()
+        {
+            var logger = new FileLogger(_category, _fileWriter, () => true, isPrimary: () => true, logType: LogType.Host);
+
+            // throw an exception so we have a stack
+            try
+            {
+                var innerEx = new InvalidOperationException("boom!");
+                var ex = new FunctionInvocationException("Error executing function.", innerEx);
+                throw ex;
+            }
+            catch (Exception ex)
+            {
+                logger.LogError(ex, "Test Message");
+            }
+
+            _fileWriter.Flush();
+
+            string logFile = Directory.EnumerateFiles(_logFilePath).Single();
+            string[] lines = File.ReadAllLines(logFile);
+
+            // A FunctionInvocationException only logs the message.
+            Assert.Collection(lines,
+                t => Assert.EndsWith("[Error] Test Message", t),
+                t => Assert.Equal("boom!", t));
+        }
+
+        [Fact]
+        public void FileLogger_LogsException()
+        {
+            var logger = new FileLogger(_category, _fileWriter, () => true, isPrimary: () => true, logType: LogType.Host);
+
+            // throw an exception so we have a stack
+            try
+            {
+                var ex = new InvalidOperationException("boom!");
+                throw ex;
+            }
+            catch (Exception ex)
+            {
+                logger.LogError(ex, "Test Message");
+            }
+
+            _fileWriter.Flush();
+
+            string logFile = Directory.EnumerateFiles(_logFilePath).Single();
+            string[] lines = File.ReadAllLines(logFile);
+
+            // This isn't a FunctionInvocationException, which means we'll see the stack.
+            Assert.Collection(lines,
+                t => Assert.EndsWith("[Error] Test Message", t),
+                t => Assert.Equal("System.InvalidOperationException : boom!", t),
+                t => Assert.Contains("at Microsoft.Azure.WebJobs.Script.Tests.Diagnostics.FileLoggerTests.FileLogger_LogsException()", t));
+        }
+
         [Fact]
         public void GetLogPrefix_ReturnsExpectedValue()
         {