CSHARP-4870: CreateCluster throws NullReferenceException when not setting LoggingSettings (#1236)

Author: BorisDog

src/MongoDB.Driver.Core/Core/Clusters/ClusterFactory.cs

@@ -110,6 +110,11 @@ private LoadBalancedCluster CreateLoadBalancedCluster(ClusterSettings setting)
 
         private void ProcessClusterEnvironment(ClusterSettings settings)
         {
+            if (_loggerFactory == null)
+            {
+                return;
+            }
+
             foreach (var (host, _) in  settings.EndPoints.Select(EndPointHelper.GetHostAndPort))
             {
                 if (LogIfCosmosDB(host) || LogIfDocumentDB(host))
@@ -129,7 +134,7 @@ bool LogIfExternalEnvironment(string host, string environment, string documentat
                 if (suffixes.Any(s => host.EndsWith(s, StringComparison.InvariantCultureIgnoreCase)))
                 {
                     var logger = _loggerFactory.CreateLogger<LogCategories.Client>();
-                    logger.LogInformation("You appear to be connected to a {environment} cluster. For more information regarding feature compatibility and support please visit {url}", environment, documentationUrl);
+                    logger?.LogInformation("You appear to be connected to a {environment} cluster. For more information regarding feature compatibility and support please visit {url}", environment, documentationUrl);
 
                     return true;
                 }

tests/MongoDB.Driver.Core.Tests/Core/Clusters/ClusterFactoryTests.cs

@@ -35,6 +35,16 @@ public ClusterFactoryTests(ITestOutputHelper output) : base(output)
         {
         }
 
+        [Fact]
+        public void ClusterFactory_should_create_cluster_when_loggerfactory_is_not_set()
+        {
+            const string connectionString = "mongodb://a.MONGO.COSMOS.AZURE.COM:19555";
+            var subject = CreateSubject(connectionString, null);
+            var cluster = subject.CreateCluster();
+
+            cluster.Should().NotBeNull();
+        }
+
         [Theory]
         [InlineData("mongodb://a.MONGO.COSMOS.AZURE.COM:19555", ExpectedCosmosDBMessage)]
         [InlineData("mongodb://a.MONGO.COSMOS.AZURE.COM:19555", ExpectedCosmosDBMessage)]
@@ -59,7 +69,7 @@ public ClusterFactoryTests(ITestOutputHelper output) : base(output)
         [InlineData("mongodb://a.mongo.cosmos.azure.com:19554,b.docdb-elastic.amazonaws.com:27017,c.mongo.cosmos.azure.com:19555/", ExpectedCosmosDBMessage)]
         public void ClusterFactory_should_log_if_external_environment_is_detected(string connectionString, string expectedMessage)
         {
-            var subject = CreateSubject(connectionString);
+            var subject = CreateSubject(connectionString, LoggerFactory);
             _ = subject.CreateCluster();
 
             var logs = GetLogs();
@@ -77,22 +87,22 @@ public void ClusterFactory_should_log_if_external_environment_is_detected(string
         [InlineData("mongodb+srv://a.docdb-elastic.amazonaws.com.tld/")]
         public void ClusterFactory_should_not_log_if_no_external_environment_is_detected(string connectionString)
         {
-            var subject = CreateSubject(connectionString);
+            var subject = CreateSubject(connectionString, LoggerFactory);
             _ = subject.CreateCluster();
 
             var logs = GetLogs();
             logs.Length.Should().Be(0);
         }
 
-        private ClusterFactory CreateSubject(string connectionString)
+        private ClusterFactory CreateSubject(string connectionString, ILoggerFactory loggerFactory)
         {
             var parsedConnectionString = new ConnectionString(connectionString);
 
             var eventSubscriberMock = Mock.Of<IEventSubscriber>();
             var serverFactoryMock = Mock.Of<IClusterableServerFactory>();
 
             var clusterSettings = new ClusterSettings(endPoints: Optional.Enumerable(parsedConnectionString.Hosts));
-            var clusterFactory = new ClusterFactory(clusterSettings, serverFactoryMock, eventSubscriberMock, LoggerFactory);
+            var clusterFactory = new ClusterFactory(clusterSettings, serverFactoryMock, eventSubscriberMock, loggerFactory);
 
             return clusterFactory;
         }