Enable null-state analysis

Annotate nullable reference types to resolve warnings.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>

Author: kevinoid

Directory.Build.props

@@ -32,7 +32,7 @@
       https://github.com/dotnet/roslyn/issues/37995#issuecomment-531549082),
       and/or using the Nullable NuGet package.
     -->
-    <Nullable>disable</Nullable>
+    <Nullable>enable</Nullable>
 
     <!--
       Include full paths in compiler output for Omnisharp.

KevinLocke.DataSetChecker.UnitTests/XPathFinderTests.cs

@@ -15,7 +15,7 @@ public static class XPathFinderTests
         public static void FindXPath_ThrowsOnNull()
         {
             XPathFinder finder = new();
-            Assert.Throws<ArgumentNullException>(() => finder.FindXPath(null));
+            Assert.Throws<ArgumentNullException>(() => finder.FindXPath(null!));
         }
 
         [Fact]

KevinLocke.DataSetChecker/DataSetChecker.cs

@@ -52,7 +52,7 @@ public class DataSetChecker : IDisposable
             new(@"^[\p{L}\p{Nd}@#$_]+$", RegexOptions.Compiled | RegexOptions.CultureInvariant);
 
         private readonly SqlConnection sqlConnectionFmtOnly;
-        private readonly SqlConnection sqlConnectionSpDescribe;
+        private readonly SqlConnection? sqlConnectionSpDescribe;
         private bool disposedValue;
 
         /// <summary>
@@ -99,7 +99,7 @@ public DataSetChecker(string connectionString)
             }
         }
 
-        public event EventHandler<DataSetCheckerEventArgs> DataSetCheckerEventHandler;
+        public event EventHandler<DataSetCheckerEventArgs>? DataSetCheckerEventHandler;
 
         /// <summary>
         /// Entry-point to check a named XSD against a given collection.
@@ -136,7 +136,7 @@ public static int Main(string[] args)
             }
 
             int exitCode = 0;
-            using (DataSetChecker checker = new(options.ConnectionString))
+            using (DataSetChecker checker = new(options.ConnectionString!))
             {
                 checker.DataSetCheckerEventHandler += (object sender, DataSetCheckerEventArgs eventArgs) =>
                 {
@@ -247,8 +247,8 @@ protected void CheckDbCommand(XmlNode dbCommand)
                 throw new ArgumentNullException(nameof(dbCommand));
             }
 
-            string commandText = null;
-            List<SqlParameter> sqlParameters = null;
+            string? commandText = null;
+            List<SqlParameter>? sqlParameters = null;
             foreach (XmlNode childNode in dbCommand.ChildNodes)
             {
                 if (childNode.NamespaceURI != DataSetConstants.MsDsNamespace)
@@ -391,7 +391,7 @@ protected void CheckDbCommand(XmlNode dbCommand)
         protected void CheckCommand(
             string commandText,
             CommandType commandType,
-            ICollection<SqlParameter> sqlParameters)
+            ICollection<SqlParameter>? sqlParameters)
         {
             if (this.sqlConnectionSpDescribe != null)
             {
@@ -400,7 +400,7 @@ protected void CheckCommand(
 
             if (this.sqlConnectionFmtOnly != null)
             {
-                SqlParameter[] sqlParametersArray = null;
+                SqlParameter[]? sqlParametersArray = null;
                 if (sqlParameters != null)
                 {
                     sqlParametersArray = new SqlParameter[sqlParameters.Count];
@@ -418,7 +418,7 @@ protected void CheckCommand(
         protected void CheckCommandFormatOnly(
             string commandText,
             CommandType commandType,
-            SqlParameter[] sqlParameters)
+            SqlParameter[]? sqlParameters)
         {
             using SqlCommand sqlCommand = new(commandText, this.sqlConnectionFmtOnly);
             sqlCommand.CommandType = commandType;
@@ -432,7 +432,7 @@ protected void CheckCommandFormatOnly(
 
         protected void CheckCommandSPDescribe(
             string commandText,
-            IEnumerable<SqlParameter> sqlParameters)
+            IEnumerable<SqlParameter>? sqlParameters)
         {
             string paramsDecl = this.GetSqlDeclaration(sqlParameters);
             using SqlCommand sqlCommand = new("sp_describe_first_result_set", this.sqlConnectionSpDescribe);
@@ -572,7 +572,7 @@ private static XmlNamespaceManager CreateNamespaceManager()
         }
 
         // FIXME: Is this really not implemented somewhere in ADO.NET?
-        private string GetSqlDeclaration(IEnumerable<SqlParameter> parameters)
+        private string GetSqlDeclaration(IEnumerable<SqlParameter>? parameters)
         {
             if (parameters == null)
             {
@@ -612,7 +612,7 @@ private string GetSqlDeclaration(IEnumerable<SqlParameter> parameters)
             return declaration.ToString(0, declaration.Length - 2);
         }
 
-        private void LogError(string message, XmlNode node, Exception exception = null)
+        private void LogError(string message, XmlNode? node, Exception? exception = null)
         {
             // FIXME: Throw if no EventHandler?
             DataSetCheckerEventArgs eventArgs = new(
@@ -623,7 +623,7 @@ private void LogError(string message, XmlNode node, Exception exception = null)
             this.OnDataSetCheckerEventHandler(eventArgs);
         }
 
-        private void LogWarning(string message, XmlNode node, Exception exception = null)
+        private void LogWarning(string message, XmlNode? node, Exception? exception = null)
         {
             // FIXME: Throw if no EventHandler?
             DataSetCheckerEventArgs eventArgs = new(

KevinLocke.DataSetChecker/DataSetCheckerEventArgs.cs

@@ -15,19 +15,19 @@ public class DataSetCheckerEventArgs : EventArgs
     {
         private static readonly DataSetXPathFinder XPathFinder = new();
 
-        internal DataSetCheckerEventArgs(XmlSeverityType severity, string message, XmlNode node, Exception exception)
+        internal DataSetCheckerEventArgs(XmlSeverityType severity, string message, XmlNode? node, Exception? exception)
         {
             this.Message = message ?? throw new ArgumentNullException(nameof(message));
             this.Severity = severity;
             this.Node = node;
             this.Exception = exception;
         }
 
-        public Exception Exception { get; }
+        public Exception? Exception { get; }
 
         public string Message { get; }
 
-        public XmlNode Node { get; }
+        public XmlNode? Node { get; }
 
         public XmlSeverityType Severity { get; }
 

KevinLocke.DataSetChecker/DataSetCheckerSettings.cs

@@ -19,7 +19,7 @@ namespace KevinLocke.DataSetChecker
     /// </remarks>
     public class DataSetCheckerSettings
     {
-        public string ConnectionString { get; set; }
+        public string? ConnectionString { get; set; }
 
         public bool NoWarnings { get; set; }
     }

KevinLocke.DataSetChecker/XPathFinder.cs

@@ -36,18 +36,14 @@ public string FindXPath(XmlNode node)
         /// Finds an XPath expression to a given <see cref="XmlNode"/> from a
         /// given context.
         /// </summary>
-        /// <param name="node">Node which the returned XPath will select.</param>
+        /// <param name="target">Node which the returned XPath will select.</param>
         /// <param name="context">Node from which the XPath will be run.
         /// If <c>null</c>, an absolute XPath is returned.</param>
-        /// <returns>An XPath expression which selects <paramref name="node"/>
+        /// <returns>An XPath expression which selects <paramref name="target"/>
         /// when run from <paramref name="context"/>.</returns>
-        public virtual string FindXPath(XmlNode node, XmlNode context)
+        public virtual string FindXPath(XmlNode target, XmlNode? context)
         {
-            if (node == null)
-            {
-                throw new ArgumentNullException(nameof(node));
-            }
-
+            XmlNode? node = target ?? throw new ArgumentNullException(nameof(target));
             List<string> steps = [];
             while (node != null && node != context)
             {