Nullable and modernization part 6 (#132)

* Expand nullability to 'object message' for logger, loggerextensions. More 'is' conversions.

* Seal some classes, reduce doc redundancy, reduce some nullables

* inerpolate string

src/Directory.Build.props

@@ -3,5 +3,6 @@
         <UseSharedCompilation>true</UseSharedCompilation>
         <LangVersion>latest</LangVersion>
         <Nullable>Enable</Nullable>
+        <WarningsAsErrors>nullable</WarningsAsErrors>
     </PropertyGroup>
 </Project>

src/log4net.Tests/Appender/DebugAppenderTest.cs

@@ -138,7 +138,7 @@ public void MethodNameCategoryTest()
       Debug.Listeners.Remove(categoryTraceListener);
     }
 
-    private class TestErrorHandler : IErrorHandler
+    private sealed class TestErrorHandler : IErrorHandler
     {
       public bool ErrorOccured { get; private set; }
 

src/log4net.Tests/Appender/RollingFileAppenderTest.cs

@@ -1441,7 +1441,7 @@ public void TestInitializeCountUpInfinite3()
       appender.Encoding = Encoding.ASCII;
       appender.ErrorHandler = handler;
       appender.MaxSizeRollBackups = maxSizeRollBackups;
-      if (lockModel != null)
+      if (lockModel is not null)
       {
         appender.LockingModel = lockModel;
       }

src/log4net.Tests/Appender/SmtpPickupDirAppenderTest.cs

@@ -37,7 +37,7 @@ public class SmtpPickupDirAppenderTest
   {
     private readonly string _testPickupDir;
 
-    private class SilentErrorHandler : IErrorHandler
+    private sealed class SilentErrorHandler : IErrorHandler
     {
       private readonly StringBuilder m_buffer = new();
 

src/log4net.Tests/Core/DefaultRepositorySelectorTest.cs

@@ -182,5 +182,5 @@ public IAppender[] GetAppenders()
     }
   }
 
-  internal class MockLoggerRepository2 : MockLoggerRepository;
+  internal sealed class MockLoggerRepository2 : MockLoggerRepository;
 }

src/log4net.Tests/Core/FixingTest.cs

@@ -37,7 +37,7 @@ public void CreateRepository()
     {
       bool exists = false;
       Repository.ILoggerRepository[] repositories = LogManager.GetAllRepositories();
-      if (repositories != null)
+      if (repositories is not null)
       {
         foreach (Repository.ILoggerRepository r in repositories)
         {
@@ -54,7 +54,7 @@ public void CreateRepository()
       }
 
       // write-once
-      if (Thread.CurrentThread.Name == null)
+      if (Thread.CurrentThread.Name is null)
       {
         Thread.CurrentThread.Name = "Log4Net Test thread";
       }

src/log4net.Tests/Core/StringFormatTest.cs

@@ -108,7 +108,15 @@ public void TestFormatString()
       Assert.AreEqual(STRING_FORMAT_ERROR, stringAppender.GetString(), "Test formatting error");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Debug(null);
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Debug(null, new Exception("Exception message"));
+      Assert.AreEqual("System.Exception: Exception message" + Environment.NewLine, stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.InfoFormat("One{0} null", null);
       Assert.AreEqual("One null", stringAppender.GetString());
       stringAppender.Reset();
@@ -197,7 +205,15 @@ public void TestLogFormatApi_Debug()
       Assert.AreEqual("DEBUG:Before Middle After End", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Debug(null);
+      Assert.AreEqual("DEBUG:", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Debug(null, new Exception("Exception message"));
+      Assert.AreEqual("DEBUG:System.Exception: Exception message" + Environment.NewLine, stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.DebugFormat("One{0} null", null);
       Assert.AreEqual("DEBUG:One null", stringAppender.GetString());
       stringAppender.Reset();
@@ -285,7 +301,15 @@ public void TestLogFormatApi_NoDebug()
       Assert.AreEqual("", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Debug(null);
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Debug(null, new Exception("Exception message"));
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.DebugFormat("One{0} null", null);
       Assert.AreEqual("", stringAppender.GetString());
       stringAppender.Reset();
@@ -372,7 +396,15 @@ public void TestLogFormatApi_Info()
       Assert.AreEqual("INFO:Before Middle After End", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Info(null);
+      Assert.AreEqual("INFO:", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Info(null, new Exception("Exception message"));
+      Assert.AreEqual("INFO:System.Exception: Exception message" + Environment.NewLine, stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.InfoFormat("One{0} null", null);
       Assert.AreEqual("INFO:One null", stringAppender.GetString());
       stringAppender.Reset();
@@ -460,7 +492,15 @@ public void TestLogFormatApi_NoInfo()
       Assert.AreEqual("", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Info(null);
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Info(null, new Exception("Exception message"));
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.InfoFormat("One{0} null", null);
       Assert.AreEqual("", stringAppender.GetString());
       stringAppender.Reset();
@@ -547,7 +587,15 @@ public void TestLogFormatApi_Warn()
       Assert.AreEqual("WARN:Before Middle After End", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Warn(null);
+      Assert.AreEqual("WARN:", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Warn(null, new Exception("Exception message"));
+      Assert.AreEqual("WARN:System.Exception: Exception message" + Environment.NewLine, stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.WarnFormat("One{0} null", null);
       Assert.AreEqual("WARN:One null", stringAppender.GetString());
       stringAppender.Reset();
@@ -635,7 +683,15 @@ public void TestLogFormatApi_NoWarn()
       Assert.AreEqual("", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Warn(null);
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Warn(null, new Exception("Exception message"));
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.WarnFormat("One{0} null", null);
       Assert.AreEqual("", stringAppender.GetString());
       stringAppender.Reset();
@@ -722,7 +778,15 @@ public void TestLogFormatApi_Error()
       Assert.AreEqual("ERROR:Before Middle After End", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Error(null);
+      Assert.AreEqual("ERROR:", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Error(null, new Exception("Exception message"));
+      Assert.AreEqual("ERROR:System.Exception: Exception message" + Environment.NewLine, stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.ErrorFormat("One{0} null", null);
       Assert.AreEqual("ERROR:One null", stringAppender.GetString());
       stringAppender.Reset();
@@ -810,7 +874,15 @@ public void TestLogFormatApi_NoError()
       Assert.AreEqual("", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Error(null);
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Error(null, new Exception("Exception message"));
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.ErrorFormat("One{0} null", null);
       Assert.AreEqual("", stringAppender.GetString());
       stringAppender.Reset();
@@ -897,7 +969,15 @@ public void TestLogFormatApi_Fatal()
       Assert.AreEqual("FATAL:Before Middle After End", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Fatal(null);
+      Assert.AreEqual("FATAL:", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Fatal(null, new Exception("Exception message"));
+      Assert.AreEqual("FATAL:System.Exception: Exception message" + Environment.NewLine, stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.FatalFormat("One{0} null", null);
       Assert.AreEqual("FATAL:One null", stringAppender.GetString());
       stringAppender.Reset();
@@ -985,7 +1065,15 @@ public void TestLogFormatApi_NoFatal()
       Assert.AreEqual("", stringAppender.GetString(), "Test formatting with 'en' provider");
       stringAppender.Reset();
 
-      // ***
+      // *** Nulls
+      log1.Fatal(null);
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
+      log1.Fatal(null, new Exception("Exception message"));
+      Assert.AreEqual("", stringAppender.GetString());
+      stringAppender.Reset();
+
       log1.FatalFormat("One{0} null", null);
       Assert.AreEqual("", stringAppender.GetString());
       stringAppender.Reset();

src/log4net.Tests/DateFormatter/AbsoluteTimeDateFormatterTest.cs

@@ -114,7 +114,7 @@ override protected void FormatDateWithoutMillis(DateTime dateToFormat, StringBui
     }
   }
 
-  internal class FormatterTwo : FormatterOne
+  internal sealed class FormatterTwo : FormatterOne
   {
   }
 }

src/log4net.Tests/Hierarchy/XmlHierarchyConfiguratorTest.cs

@@ -57,7 +57,7 @@ private void SetTestPropWithPath()
     }
 
     // workaround for SetParameter being protected
-    private class TestConfigurator : XmlHierarchyConfigurator
+    private sealed class TestConfigurator : XmlHierarchyConfigurator
     {
       public TestConfigurator() : base(null!)
       {

src/log4net.Tests/Layout/PatternLayoutTest.cs

@@ -310,7 +310,7 @@ public void NamedPatternConverterWithPrecision2ShouldStripLessLeadingStuffIfPres
     /// <summary>
     /// Converter to include event message
     /// </summary>
-    private class TestMessagePatternConverter : PatternLayoutConverter
+    private sealed class TestMessagePatternConverter : PatternLayoutConverter
     {
       /// <summary>
       /// Convert the pattern to the rendered message
@@ -344,7 +344,7 @@ public void TestExceptionPattern()
       stringAppender.Reset();
     }
 
-    private class MessageAsNamePatternConverter : NamedPatternConverter
+    private sealed class MessageAsNamePatternConverter : NamedPatternConverter
     {
       protected override string GetFullyQualifiedName(LoggingEvent loggingEvent)
       {

src/log4net.Tests/Util/PatternStringTest.cs

@@ -75,11 +75,11 @@ public void TestAppSettingPathConverter()
       }
       finally
       {
-        if (appDomain != null)
+        if (appDomain is not null)
         {
           AppDomain.Unload(appDomain);
         }
-        if (configurationFileName != null)
+        if (configurationFileName is not null)
         {
           File.Delete(configurationFileName);
         }

src/log4net/Appender/AdoNetAppender.cs

@@ -376,15 +376,15 @@ protected override void OnClose()
     /// </remarks>
     protected override void SendBuffer(LoggingEvent[] events)
     {
-      if (ReconnectOnError && (Connection == null || Connection.State != ConnectionState.Open))
+      if (ReconnectOnError && (Connection is null || Connection.State != ConnectionState.Open))
       {
-        LogLog.Debug(declaringType, $"Attempting to reconnect to database. Current Connection State: {((Connection == null) ? SystemInfo.NullText : Connection.State.ToString())}");
+        LogLog.Debug(declaringType, $"Attempting to reconnect to database. Current Connection State: {((Connection is null) ? SystemInfo.NullText : Connection.State.ToString())}");
 
         InitializeDatabaseConnection();
       }
 
       // Check that the connection exists and is open
-      if (Connection != null && Connection.State == ConnectionState.Open)
+      if (Connection is not null && Connection.State == ConnectionState.Open)
       {
         if (UseTransactions)
         {
@@ -462,7 +462,7 @@ protected virtual void SendBuffer(IDbTransaction? dbTran, LoggingEvent[] events)
           // Set the command type
           dbCmd.CommandType = CommandType;
           // Send buffer using the prepared command object
-          if (dbTran != null)
+          if (dbTran is not null)
           {
             dbCmd.Transaction = dbTran;
           }
@@ -474,7 +474,7 @@ protected virtual void SendBuffer(IDbTransaction? dbTran, LoggingEvent[] events)
           }
           catch (Exception)
           {
-            if (dbTran != null)
+            if (dbTran is not null)
             {
               // rethrow exception in transaction mode, cuz now transaction is in failed state
               throw;
@@ -503,7 +503,7 @@ protected virtual void SendBuffer(IDbTransaction? dbTran, LoggingEvent[] events)
         // create a new command
         using (IDbCommand dbCmd = Connection!.CreateCommand())
         {
-          if (dbTran != null)
+          if (dbTran is not null)
           {
             dbCmd.Transaction = dbTran;
           }
@@ -550,7 +550,7 @@ protected virtual void Prepare(IDbCommand dbCmd)
     /// </returns>
     protected virtual string GetLogStatement(LoggingEvent logEvent)
     {
-      if (Layout == null)
+      if (Layout is null)
       {
         ErrorHandler.Error("AdoNetAppender: No Layout specified.");
         return "";
@@ -587,7 +587,7 @@ protected virtual IDbConnection CreateConnection(Type connectionType, string con
     /// <returns>A connection string used to connect to the database.</returns>
     protected virtual string ResolveConnectionString(out string connectionStringContext)
     {
-      if (ConnectionString != null && ConnectionString.Length > 0)
+      if (ConnectionString is not null && ConnectionString.Length > 0)
       {
         connectionStringContext = "ConnectionString";
         return ConnectionString;
@@ -596,7 +596,7 @@ protected virtual string ResolveConnectionString(out string connectionStringCont
       if (!String.IsNullOrEmpty(ConnectionStringName))
       {
         ConnectionStringSettings settings = ConfigurationManager.ConnectionStrings[ConnectionStringName!];
-        if (settings != null)
+        if (settings is not null)
         {
           connectionStringContext = "ConnectionStringName";
           return settings.ConnectionString;
@@ -607,7 +607,7 @@ protected virtual string ResolveConnectionString(out string connectionStringCont
         }
       }
 
-      if (AppSettingsKey != null && AppSettingsKey.Length > 0)
+      if (AppSettingsKey is not null && AppSettingsKey.Length > 0)
       {
         connectionStringContext = "AppSettingsKey";
         string? appSettingsConnectionString = SystemInfo.GetAppSetting(AppSettingsKey);
@@ -694,7 +694,7 @@ private void InitializeDatabaseConnection()
     /// </remarks>
     private void DisposeConnection()
     {
-      if (Connection != null)
+      if (Connection is not null)
       {
         try
         {

src/log4net/Appender/AppenderSkeleton.cs

@@ -72,7 +72,7 @@ protected AppenderSkeleton()
       // There is no point in closing twice.
       if (!m_closed)
       {
-        LogLog.Debug(declaringType, "Finalizing appender named [" + Name + "].");
+        LogLog.Debug(declaringType, $"Finalizing appender named [{Name}].");
         Close();
       }
     }