replace log error with raise exception when format output is invalid

Author: amirkaws

libraries/src/AWS.Lambda.Powertools.Logging/Internal/PowertoolsLogger.cs

@@ -345,25 +345,14 @@ private object GetFormattedLogEntry(LogLevel logLevel, DateTime timestamp, objec
         try
         {
             var logObject = logFormatter.FormatLogEntry(logEntry);
-            if (logObject is not null)
-                return logObject;
-
-            return new
-            {
-                logEntry.Timestamp,
-                Level = LogLevel.Error.ToString(),
-                Message = $"{logFormatter.GetType().FullName} returned null value"
-            };
+            if (logObject is null)
+                throw new LogFormatException($"{logFormatter.GetType().FullName} returned Null value.");
+            return logObject;
         }
         catch (Exception e)
         {
-            return new
-            {
-                logEntry.Timestamp,
-                Level = LogLevel.Error.ToString(),
-                Message = $"{logFormatter.GetType().FullName} raised error: {e.Message}.",
-                Exception = e
-            };
+            throw new LogFormatException(
+                $"{logFormatter.GetType().FullName} raised an exception: {e.Message}.", e);
         }
     }
 

libraries/src/AWS.Lambda.Powertools.Logging/LogFormatException.cs

@@ -0,0 +1,41 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ * 
+ *  http://aws.amazon.com/apache2.0
+ * 
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+using System;
+
+namespace AWS.Lambda.Powertools.Logging;
+
+/// <summary>
+/// Exception thrown when LogFormatter returns invalid object or error:
+/// </summary>
+public class LogFormatException : Exception
+{
+    /// <summary>
+    /// Creates a new IdempotencyConfigurationException
+    /// </summary>
+    public LogFormatException()
+    {
+    }
+
+    /// <inheritdoc />
+    public LogFormatException(string message) : base(message)
+    {
+    }
+
+    /// <inheritdoc />
+    public LogFormatException(string message, Exception innerException) : base(message, innerException)
+    {
+    }
+}

libraries/tests/AWS.Lambda.Powertools.Logging.Tests/LogFormatterTest.cs

@@ -169,7 +169,7 @@ public void Log_WhenCustomFormatter_LogsCustomFormat()
     public class LogFormatterNullTest
     {
         [Fact]
-        public void Log_WhenCustomFormatterReturnNull_LogsError()
+        public void Log_WhenCustomFormatterReturnNull_ThrowsLogFormatException()
         {
             // Arrange
             var loggerName = Guid.NewGuid().ToString();
@@ -193,12 +193,13 @@ public void Log_WhenCustomFormatterReturnNull_LogsError()
                 });
 
             // Act
-            logger.LogInformation(message);
+            void Act() => logger.LogInformation(message);
 
             // Assert
+            Assert.Throws<LogFormatException>(Act);
             logFormatter.Received(1).FormatLogEntry(Arg.Any<LogEntry>());
-            systemWrapper.Received(1).LogLine(Arg.Is<string>(x => x.Contains("Error") && x.Contains("null")));
-            
+            systemWrapper.DidNotReceiveWithAnyArgs().LogLine(Arg.Any<string>());
+
             //Clean up
             Logger.UseDefaultFormatter();
         }
@@ -208,7 +209,7 @@ public void Log_WhenCustomFormatterReturnNull_LogsError()
     public class LogFormatterExceptionTest
     {
         [Fact]
-        public void Log_WhenCustomFormatterRaisesException_LogsError()
+        public void Log_WhenCustomFormatterRaisesException_ThrowsLogFormatException()
         {
             // Arrange
             var loggerName = Guid.NewGuid().ToString();
@@ -233,12 +234,13 @@ public void Log_WhenCustomFormatterRaisesException_LogsError()
                 });
 
             // Act
-            logger.LogInformation(message);
+            void Act() => logger.LogInformation(message);
 
             // Assert
+            Assert.Throws<LogFormatException>(Act);
             logFormatter.Received(1).FormatLogEntry(Arg.Any<LogEntry>());
-            systemWrapper.Received(1).LogLine(Arg.Is<string>(x => x.Contains("Error") && x.Contains(errorMessage)));
-            
+            systemWrapper.DidNotReceiveWithAnyArgs().LogLine(Arg.Any<string>());
+
             //Clean up
             Logger.UseDefaultFormatter();
         }