Prepare System.Xaml for nullable reference type annotations (#8520)

* start process of annotating System.Xaml for NRT

* showcase: annotate EventConverter

Author: halgab

src/Microsoft.DotNet.Wpf/src/Common/src/System/SR.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System;
 using System.Resources;
 using System.Runtime.CompilerServices;

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/CriticalExceptions.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System;
 
 #if PBTCOMPILER

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/FriendAccessAllowedAttribute.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 // Description: Implementation of a FriendAccessAllowedAttribute attribute that is used to mark internal metadata
 //              that is allowed to be accessed from friend assemblies.
 
@@ -10,7 +12,7 @@
 #if WINDOWS_BASE
 namespace MS.Internal.WindowsBase
 #elif PRESENTATION_CORE
-namespace MS.Internal.PresentationCore 
+namespace MS.Internal.PresentationCore
 #elif PRESENTATIONFRAMEWORK
 namespace MS.Internal.PresentationFramework
 #elif PRESENTATION_CFF_RASTERIZER

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/SafeSecurityHelper.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 // Purpose:  Helper functions that require elevation but are safe to use.
 
 using System;

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/SecurityCriticalDataForSet.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 // Description:
 //              This is a helper class to facilate the storage of data that's Critical for set.
 //              The data itself is not information disclosure but the value controls a critical
@@ -10,7 +12,7 @@
 //              For example a filepath variable might control what part of the file system the
 //              code gets access to.
 
-using System ; 
+using System ;
 using System.Security ;
 
 #if WINDOWS_BASE
@@ -43,11 +45,11 @@ namespace MS.Internal
     internal struct SecurityCriticalDataForSet<T>
     {
         internal SecurityCriticalDataForSet(T value)
-        { 
-            _value = value; 
+        {
+            _value = value;
         }
 
-        internal T Value 
+        internal T Value
         {
         #if DEBUG
             [System.Diagnostics.DebuggerStepThrough]

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/Xaml/Context/XamlContextStack.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Text;
@@ -111,7 +113,7 @@ public void PushScope()
             Debug.Assert(CurrentFrame.Depth == Depth);
         }
 
-        //Consumers of this stack call PopScope, and we'll move the currentFrame from the main 
+        //Consumers of this stack call PopScope, and we'll move the currentFrame from the main
         // linked list to the recylced linked list and call .Reset
         public void PopScope()
         {

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/Xaml/Context/XamlFrame.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Text;
@@ -28,8 +30,8 @@ protected XamlFrame(XamlFrame source)
         public virtual XamlFrame Clone()
         {
             // Clone should only be overridden for the classes that really need it
-            // ObjectWriterFrame overrides this so we can reuse the context for 
-            // Templates.  
+            // ObjectWriterFrame overrides this so we can reuse the context for
+            // Templates.
             throw new NotImplementedException();
         }
 

src/Microsoft.DotNet.Wpf/src/Shared/MS/Internal/Xaml/Parser/SpecialBracketCharacters.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 //  Description: Data model for the Bracket characters specified on a Markup Extension property.
 
 using System;
@@ -13,7 +15,7 @@
 namespace MS.Internal.Xaml.Parser
 {
     /// <summary>
-    /// Class that provides helper functions for the parser/Xaml Reader 
+    /// Class that provides helper functions for the parser/Xaml Reader
     /// to process Bracket Characters specified on a Markup Extension Property
     /// </summary>
     internal class SpecialBracketCharacters : ISupportInitialize
@@ -24,7 +26,7 @@ internal class SpecialBracketCharacters : ISupportInitialize
         private bool _initializing;
         private StringBuilder _startCharactersStringBuilder;
         private StringBuilder _endCharactersStringBuilder;
-        
+
         internal SpecialBracketCharacters()
         {
             BeginInit();
@@ -59,7 +61,7 @@ private void Tokenize(IReadOnlyDictionary<char,char> attributeList)
                 foreach (char openingBracket in attributeList.Keys)
                 {
                     char closingBracket = attributeList[openingBracket];
-                    string errorMessage = string.Empty; 
+                    string errorMessage = string.Empty;
                     if (IsValidBracketCharacter(openingBracket, closingBracket))
                     {
                         _startCharactersStringBuilder.Append(openingBracket);

src/Microsoft.DotNet.Wpf/src/Shared/MS/Utility/FrugalList.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System;
 using System.Diagnostics;
 using System.Collections;

src/Microsoft.DotNet.Wpf/src/Shared/System/Windows/Markup/ReflectionHelper.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 //
 //
 //
@@ -50,16 +52,16 @@ internal static class ReflectionHelper
         // System.Reflection.MetadataLoadContext instance
         private static MetadataLoadContext _metadataLoadContext = null;
 
-        // MetadataLoadContext Assembly cache 
-        private static Dictionary<string, Assembly> _cachedMetadataLoadContextAssemblies = null; 
-        private static Dictionary<string, Assembly> _cachedMetadataLoadContextAssembliesByNameNoExtension = null; 
+        // MetadataLoadContext Assembly cache
+        private static Dictionary<string, Assembly> _cachedMetadataLoadContextAssemblies = null;
+        private static Dictionary<string, Assembly> _cachedMetadataLoadContextAssembliesByNameNoExtension = null;
 
         // The local assembly that contains the baml.
         private static string _localAssemblyName = string.Empty;
 
         internal static void Initialize(IEnumerable<string> assemblyPaths)
-        { 
-            // System.Reflection.MetadataLoadContext Assembly cache 
+        {
+            // System.Reflection.MetadataLoadContext Assembly cache
             _cachedMetadataLoadContextAssemblies = new Dictionary<string, Assembly>(StringComparer.OrdinalIgnoreCase);
             _cachedMetadataLoadContextAssembliesByNameNoExtension = new Dictionary<string, Assembly>(StringComparer.OrdinalIgnoreCase);
             _metadataLoadContext = new MetadataLoadContext(new PathAssemblyResolver(assemblyPaths), MscorlibReflectionAssemblyName);
@@ -168,7 +170,7 @@ internal static Type GetFrameworkType(string assemblyName, Type type)
         {
 #if PBTCOMPILER
             Assembly reflectionAssembly = LoadAssembly(assemblyName, null);
-    
+
             if (reflectionAssembly != null)
             {
                 type = reflectionAssembly.GetType(type.FullName);
@@ -209,7 +211,7 @@ internal static Type GetReflectionType(object item)
                 return ictp.GetCustomType();
         }
 #endif
-        
+
 #endregion Type
 
         #region Attributes
@@ -534,13 +536,13 @@ internal static Assembly GetAlreadyReflectionOnlyLoadedAssembly(string assemblyN
         // For a given assembly name and its full path, Reflection-Only load the assembly directly
         // from the file in disk or load the file to memory and then create assembly instance from
         // memory buffer data.
-        // 
+        //
         private static Assembly ReflectionOnlyLoadAssembly(string assemblyName, string fullPathToAssembly)
         {
-            Assembly assembly = null; 
+            Assembly assembly = null;
 
-            // If the assembly path is empty, try to load assembly by name. LoadFromAssemblyName 
-            // will result in a MetadataLoadContext.Resolve event that will contain more information about the 
+            // If the assembly path is empty, try to load assembly by name. LoadFromAssemblyName
+            // will result in a MetadataLoadContext.Resolve event that will contain more information about the
             // requested assembly.
             if (String.IsNullOrEmpty(fullPathToAssembly))
             {

src/Microsoft.DotNet.Wpf/src/Shared/System/Windows/Markup/Replacements/TypeUriConverter.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System.ComponentModel;
 using System.ComponentModel.Design.Serialization;
 using System.Globalization;
@@ -23,7 +25,7 @@ public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceT
 
         public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
         {
-            return 
+            return
                 destinationType == typeof(InstanceDescriptor) ||
                 destinationType == typeof(string) ||
                 destinationType == typeof(Uri);

src/Microsoft.DotNet.Wpf/src/Shared/System/Windows/Markup/RuntimeIdentifierPropertyAttribute.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 // Description:
 //   This attribute is placed on a class to identify the property that will
 //   function as an Name for the given class

src/Microsoft.DotNet.Wpf/src/Shared/System/Windows/Markup/TypeConverterHelper.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 //  Description: Specifies that the whitespace surrounding an element should be trimmed.
 
 using System;

src/Microsoft.DotNet.Wpf/src/Shared/System/Windows/Markup/XmlCompatibilityReader.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System;
 using System.Xml;
 using System.Collections;
@@ -170,7 +172,7 @@ public override bool Read()
 
             bool more = Reader.Read(); //passed as ref arg to ReadStartElement and ReadEndElement
             bool result = false;
-          
+
             while (more)
             {
                 switch (Reader.NodeType)
@@ -279,7 +281,7 @@ private bool ReadStartElement(ref bool more)
                 }
             }
 
-            // if the element is empty (e.g. "<a ... />" and we pushed a scope then we need to set a flag 
+            // if the element is empty (e.g. "<a ... />" and we pushed a scope then we need to set a flag
             // to get rid of the scope when we hit the next element.
             // We also need to store the current elementDepth.
             if (isEmpty)

src/Microsoft.DotNet.Wpf/src/Shared/System/Windows/Markup/XmlWrappingReader.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System;
 using System.Xml;
 using System.Xml.Schema;
@@ -13,7 +15,7 @@ namespace MS.Internal.Markup
 #elif SYSTEM_XAML
 namespace System.Xaml
 #else
-namespace System.Windows.Markup 
+namespace System.Windows.Markup
 #endif
 {
     internal class XmlWrappingReader : XmlReader, IXmlLineInfo, IXmlNamespaceResolver {
@@ -23,8 +25,8 @@ internal class XmlWrappingReader : XmlReader, IXmlLineInfo, IXmlNamespaceResolve
         protected XmlReader               _reader;
         protected IXmlLineInfo            _readerAsIXmlLineInfo;
         protected IXmlNamespaceResolver   _readerAsResolver;
-    
-// 
+
+//
 // Constructor
 //
         internal XmlWrappingReader( XmlReader baseReader ) {
@@ -105,7 +107,7 @@ public override bool Read() {
         public override void Close() {
             _reader.Close();
         }
-        
+
         public override void Skip() {
             _reader.Skip();
         }
@@ -160,7 +162,7 @@ public virtual int LineNumber {
             }
         }
 
-        public virtual int LinePosition { 
+        public virtual int LinePosition {
             get {
                 return ( _readerAsIXmlLineInfo == null ) ? 0 : _readerAsIXmlLineInfo.LinePosition;
             }
@@ -181,5 +183,5 @@ protected XmlReader Reader {
         }
     }
 }
-    
+
 

src/Microsoft.DotNet.Wpf/src/System.Xaml/GlobalSuppressions.cs

@@ -2,9 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-// This file is used by Code Analysis to maintain SuppressMessage 
+#nullable disable
+
+#nullable disable// This file is used by Code Analysis to maintain SuppressMessage
 // attributes that are applied to this project.
-// Project-level suppressions either have no target or are given 
+// Project-level suppressions either have no target or are given
 // a specific target and scoped to a namespace, type, member, etc.
 
 using System.Diagnostics.CodeAnalysis;

src/Microsoft.DotNet.Wpf/src/System.Xaml/OtherAssemblyAttrs.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 //
 // This file specifies various assembly level attributes.
 //

src/Microsoft.DotNet.Wpf/src/System.Xaml/System.Xaml.csproj

@@ -2,11 +2,12 @@
   <PropertyGroup>
     <ProjectGuid>{9AC36357-34B7-40A1-95CA-FE9F46D089A7}</ProjectGuid>
     <AssemblyName>System.Xaml</AssemblyName>
-    
+
     <Platforms>AnyCPU;x64;arm64</Platforms>
     <NoWarn>$(NoWarn);0618;NU5125;0618</NoWarn>
     <DefineConstants>$(DefineConstants);OLDRESOURCES;SYSTEM_XAML</DefineConstants>
     <EnableAnalyzers>true</EnableAnalyzers>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Windows/Markup/AcceptedMarkupExtensionExpressionTypeAttribute.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 namespace System.Windows.Markup
 {
     [Obsolete("This is not used by the XAML parser. Please look at XamlSetMarkupExtensionAttribute.")]

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Windows/Markup/AmbientAttribute.cs

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable disable
+
 using System.Runtime.CompilerServices;
 
 namespace System.Windows.Markup