From 5015ee920553f306ff2b8fd8d17545ffa7c03055 Mon Sep 17 00:00:00 2001
From: Mathew Charles <mathewc@microsoft.com>
Date: Thu, 11 Feb 2021 15:23:56 -0800
Subject: [PATCH] Fixing null ref in AI logger

---
 .../ApplicationInsightsLogger.cs              | 10 ++++++-
 .../Loggers/ApplicationInsightsLoggerTests.cs | 29 +++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/src/Microsoft.Azure.WebJobs.Logging.ApplicationInsights/ApplicationInsightsLogger.cs b/src/Microsoft.Azure.WebJobs.Logging.ApplicationInsights/ApplicationInsightsLogger.cs
index 6aaf0596c..497309743 100644
--- a/src/Microsoft.Azure.WebJobs.Logging.ApplicationInsights/ApplicationInsightsLogger.cs
+++ b/src/Microsoft.Azure.WebJobs.Logging.ApplicationInsights/ApplicationInsightsLogger.cs
@@ -203,7 +203,15 @@ private void LogTrace(LogLevel logLevel, IEnumerable<KeyValuePair<string, object
             ApplyScopeAndStateProperties(properties, values);
 
             var severityLevel = GetSeverityLevel(logLevel);
-            _telemetryClient.TrackTrace(formattedMessage, severityLevel.Value, properties);
+            if (severityLevel.HasValue)
+            {
+                _telemetryClient.TrackTrace(formattedMessage, severityLevel.Value, properties);
+            }
+            else
+            {
+                // LogLevel.None maps to null, so we have to handle that specially
+                _telemetryClient.TrackTrace(formattedMessage, properties);
+            }
         }
 
         private static SeverityLevel? GetSeverityLevel(LogLevel logLevel)
diff --git a/test/Microsoft.Azure.WebJobs.Host.UnitTests/Loggers/ApplicationInsightsLoggerTests.cs b/test/Microsoft.Azure.WebJobs.Host.UnitTests/Loggers/ApplicationInsightsLoggerTests.cs
index cf32aed13..bea9e04c7 100644
--- a/test/Microsoft.Azure.WebJobs.Host.UnitTests/Loggers/ApplicationInsightsLoggerTests.cs
+++ b/test/Microsoft.Azure.WebJobs.Host.UnitTests/Loggers/ApplicationInsightsLoggerTests.cs
@@ -582,6 +582,35 @@ public void Log_Exception_LogMessage()
             Assert.Equal("Log message", exceptionTelemetry.Properties[LogConstants.FormattedMessageKey]);
         }
 
+        [Fact]
+        public void Log_LogLevelNone_Succeeds()
+        {
+            Guid scopeGuid = Guid.NewGuid();
+
+            ILogger logger = CreateLogger(_functionCategoryName);
+
+            using (logger.BeginFunctionScope(CreateFunctionInstance(scopeGuid), _hostInstanceId))
+            {
+                logger.Log(LogLevel.None, "None");
+            }
+
+            Assert.Single(_channel.Telemetries);
+            Assert.Single(_channel.Telemetries.OfType<TraceTelemetry>());
+            foreach (var telemetry in _channel.Telemetries.Cast<TraceTelemetry>())
+            {
+                Enum.TryParse(telemetry.Message, out LogLevel expectedLogLevel);
+                Assert.Equal(expectedLogLevel.ToString(), telemetry.Properties[LogConstants.LogLevelKey]);
+                Assert.Null(telemetry.SeverityLevel);
+
+                Assert.Equal(5, telemetry.Properties.Count);
+                Assert.Equal(Process.GetCurrentProcess().Id.ToString(), telemetry.Properties[LogConstants.ProcessIdKey]);
+                Assert.Equal(_functionCategoryName, telemetry.Properties[LogConstants.CategoryNameKey]);
+                Assert.Equal(telemetry.Message, telemetry.Properties[LogConstants.CustomPropertyPrefix + LogConstants.OriginalFormatKey]);
+                Assert.Equal(scopeGuid.ToString(), telemetry.Properties[LogConstants.InvocationIdKey]);
+                Assert.Equal(telemetry.Message, telemetry.Properties[LogConstants.LogLevelKey]);
+            }
+        }
+
         [Fact]
         public void DuplicateProperties_LastStateWins()
         {