From f297dc55ad069b54c363606a5cc7b4d3b20585c1 Mon Sep 17 00:00:00 2001
From: mbrzozowski <marcin.brzozowski@ihsmarkit.com>
Date: Thu, 17 Oct 2019 17:46:12 +0200
Subject: [PATCH] Fix log events not being written to Sink when exception has
 no stacktrace

A null reference exception was thrown when trying to format Exception with no stacktrace (either root or inner one). This caused log events to not be written to Sink.
---
 .../ElasticsearchJsonFormatter.cs             |  2 +-
 .../ElasticsearchJsonFormatterTests.cs        | 37 +++++++++++++++----
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/src/Serilog.Formatting.Elasticsearch/ElasticsearchJsonFormatter.cs b/src/Serilog.Formatting.Elasticsearch/ElasticsearchJsonFormatter.cs
index 13cf47c5..b0187050 100644
--- a/src/Serilog.Formatting.Elasticsearch/ElasticsearchJsonFormatter.cs
+++ b/src/Serilog.Formatting.Elasticsearch/ElasticsearchJsonFormatter.cs
@@ -247,7 +247,7 @@ protected void WriteSingleException(Exception exception, ref string delim, TextW
 
         private void WriteMultilineString(string name, string value, ref string delimeter, TextWriter output)
         {
-            string[] lines = value.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
+            var lines = value?.Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries) ?? new string[] { };
             WriteJsonArrayProperty(name, lines, ref delimeter, output);
         }
 
diff --git a/test/Serilog.Sinks.Elasticsearch.Tests/ElasticsearchJsonFormatterTests.cs b/test/Serilog.Sinks.Elasticsearch.Tests/ElasticsearchJsonFormatterTests.cs
index 6a2e1c2d..d62a611f 100644
--- a/test/Serilog.Sinks.Elasticsearch.Tests/ElasticsearchJsonFormatterTests.cs
+++ b/test/Serilog.Sinks.Elasticsearch.Tests/ElasticsearchJsonFormatterTests.cs
@@ -19,7 +19,7 @@ static LogEvent CreateLogEvent() =>
             DateTimeOffset.Now,
             LogEventLevel.Debug,
            //exception: CreateThrownException(),
-           exception: null,
+            exception: null,
             messageTemplate: new MessageTemplate(Enumerable.Empty<MessageTemplateToken>()),
             properties: Enumerable.Empty<LogEventProperty>()
         );
@@ -55,12 +55,26 @@ static void ThrowInnerException()
             throw new Exception("Test inner exception message");
         }
 
-        static LogEvent CreateLogEventWithException() =>
+        static Exception CreateThrownExceptionWithNotThrownInner()
+        {
+            Exception retEx = null;
+            try
+            {
+                throw new Exception("Test exception message", new Exception("Test inner exception message"));
+            }
+            catch (Exception ex)
+            {
+                retEx = ex;
+            }
+            return retEx;
+        }
+
+        static LogEvent CreateLogEventWithException(Exception ex) =>
         new LogEvent
         (
             DateTimeOffset.Now,
             LogEventLevel.Debug,
-            exception: CreateThrownException(),
+            exception: ex,
             messageTemplate: new MessageTemplate(Enumerable.Empty<MessageTemplateToken>()),
             properties: Enumerable.Empty<LogEventProperty>()
         );
@@ -181,7 +195,7 @@ public void When_provide_closing_delimiter_should_use_it()
         public void DefaultJsonFormater_Should_Render_Exceptions()
         {
             CheckProperties(
-                CreateLogEventWithException,
+                () => CreateLogEventWithException(CreateThrownException()),
                 new ElasticsearchJsonFormatter(),
                 result =>
                 {
@@ -205,11 +219,12 @@ public void DefaultJsonFormater_Should_Render_Exceptions()
                 });
         }
 
-        [Fact]
-        public void DefaultJsonFormater_Should_Render_Exceptions_With_StackTrace_As_Array()
+        [Theory]
+        [MemberData(nameof(TestExceptions))]
+        public void DefaultJsonFormater_Should_Render_Exceptions_With_StackTrace_As_Array(Exception exception)
         {
             CheckProperties(
-                CreateLogEventWithException,
+                () => CreateLogEventWithException(exception),
                 new ElasticsearchJsonFormatter(formatStackTraceAsArray: true),
                 result =>
                 {
@@ -232,5 +247,13 @@ public void DefaultJsonFormater_Should_Render_Exceptions_With_StackTrace_As_Arra
                     Assert.StartsWith("[", stackTraceValue);
                 });
         }
+
+        public static IEnumerable<object[]> TestExceptions =>
+            new List<object[]>
+            {
+                new object[] { CreateThrownException() },
+                new object[] { CreateThrownExceptionWithNotThrownInner() },
+                new object[] { new Exception("Not thrown exception message") }
+            };
     }
 }