Add nullability to HtmlAbstractions (#22275)

Addresses #5680

src/Html/Abstractions/ref/Microsoft.AspNetCore.Html.Abstractions.csproj

@@ -2,6 +2,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>$(DefaultNetCoreTargetFramework)</TargetFrameworks>
+    <Nullable>annotations</Nullable>
   </PropertyGroup>
   <ItemGroup Condition="'$(TargetFramework)' == '$(DefaultNetCoreTargetFramework)'">
     <Compile Include="Microsoft.AspNetCore.Html.Abstractions.netcoreapp.cs" />

src/Html/Abstractions/ref/Microsoft.AspNetCore.Html.Abstractions.netcoreapp.cs

@@ -3,15 +3,16 @@
 
 namespace Microsoft.AspNetCore.Html
 {
+    [System.Diagnostics.DebuggerDisplayAttribute("{DebuggerToString()}")]
     public partial class HtmlContentBuilder : Microsoft.AspNetCore.Html.IHtmlContent, Microsoft.AspNetCore.Html.IHtmlContentBuilder, Microsoft.AspNetCore.Html.IHtmlContentContainer
     {
         public HtmlContentBuilder() { }
         public HtmlContentBuilder(System.Collections.Generic.IList<object> entries) { }
         public HtmlContentBuilder(int capacity) { }
         public int Count { get { throw null; } }
-        public Microsoft.AspNetCore.Html.IHtmlContentBuilder Append(string unencoded) { throw null; }
+        public Microsoft.AspNetCore.Html.IHtmlContentBuilder Append(string? unencoded) { throw null; }
-        public Microsoft.AspNetCore.Html.IHtmlContentBuilder AppendHtml(Microsoft.AspNetCore.Html.IHtmlContent htmlContent) { throw null; }
+        public Microsoft.AspNetCore.Html.IHtmlContentBuilder AppendHtml(Microsoft.AspNetCore.Html.IHtmlContent? htmlContent) { throw null; }
-        public Microsoft.AspNetCore.Html.IHtmlContentBuilder AppendHtml(string encoded) { throw null; }
+        public Microsoft.AspNetCore.Html.IHtmlContentBuilder AppendHtml(string? encoded) { throw null; }
         public Microsoft.AspNetCore.Html.IHtmlContentBuilder Clear() { throw null; }
         public void CopyTo(Microsoft.AspNetCore.Html.IHtmlContentBuilder destination) { }
         public void MoveTo(Microsoft.AspNetCore.Html.IHtmlContentBuilder destination) { }
@@ -32,7 +33,7 @@ namespace Microsoft.AspNetCore.Html
     [System.Diagnostics.DebuggerDisplayAttribute("{DebuggerToString()}")]
     public partial class HtmlFormattableString : Microsoft.AspNetCore.Html.IHtmlContent
     {
-        public HtmlFormattableString(System.IFormatProvider formatProvider, string format, params object[] args) { }
+        public HtmlFormattableString(System.IFormatProvider? formatProvider, string format, params object[] args) { }
         public HtmlFormattableString(string format, params object[] args) { }
         public void WriteTo(System.IO.TextWriter writer, System.Text.Encodings.Web.HtmlEncoder encoder) { }
     }
@@ -40,8 +41,8 @@ namespace Microsoft.AspNetCore.Html
     {
         public static readonly Microsoft.AspNetCore.Html.HtmlString Empty;
         public static readonly Microsoft.AspNetCore.Html.HtmlString NewLine;
-        public HtmlString(string value) { }
+        public HtmlString(string? value) { }
-        public string Value { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
+        public string? Value { [System.Runtime.CompilerServices.CompilerGeneratedAttribute] get { throw null; } }
         public override string ToString() { throw null; }
         public void WriteTo(System.IO.TextWriter writer, System.Text.Encodings.Web.HtmlEncoder encoder) { }
     }

src/Html/Abstractions/src/HtmlContentBuilder.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Text.Encodings.Web;
 
@@ -11,6 +12,7 @@ namespace Microsoft.AspNetCore.Html
     /// <summary>
     /// An <see cref="IHtmlContentBuilder"/> implementation using an in memory list.
     /// </summary>
+    [DebuggerDisplay("{DebuggerToString()}")]
     public class HtmlContentBuilder : IHtmlContentBuilder
     {
         /// <summary>
@@ -61,7 +63,7 @@ namespace Microsoft.AspNetCore.Html
         internal IList<object> Entries { get; }
 
         /// <inheritdoc />
-        public IHtmlContentBuilder Append(string unencoded)
+        public IHtmlContentBuilder Append(string? unencoded)
         {
             if (!string.IsNullOrEmpty(unencoded))
             {
@@ -72,7 +74,7 @@ namespace Microsoft.AspNetCore.Html
         }
 
         /// <inheritdoc />
-        public IHtmlContentBuilder AppendHtml(IHtmlContent htmlContent)
+        public IHtmlContentBuilder AppendHtml(IHtmlContent? htmlContent)
         {
             if (htmlContent == null)
             {
@@ -84,7 +86,7 @@ namespace Microsoft.AspNetCore.Html
         }
 
         /// <inheritdoc />
-        public IHtmlContentBuilder AppendHtml(string encoded)
+        public IHtmlContentBuilder AppendHtml(string? encoded)
         {
             if (!string.IsNullOrEmpty(encoded))
             {
@@ -113,13 +115,11 @@ namespace Microsoft.AspNetCore.Html
             {
                 var entry = Entries[i];
 
-                string entryAsString;
+                if (entry is string entryAsString)
-                IHtmlContentContainer entryAsContainer;
-                if ((entryAsString = entry as string)  != null)
                 {
                     destination.Append(entryAsString);
                 }
-                else if ((entryAsContainer = entry as IHtmlContentContainer) != null)
+                else if (entry is IHtmlContentContainer entryAsContainer)
                 {
                     // Since we're copying, do a deep flatten.
                     entryAsContainer.CopyTo(destination);
@@ -144,13 +144,11 @@ namespace Microsoft.AspNetCore.Html
             {
                 var entry = Entries[i];
 
-                string entryAsString;
+                if (entry is string entryAsString)
-                IHtmlContentContainer entryAsContainer;
-                if ((entryAsString = entry as string) != null)
                 {
                     destination.Append(entryAsString);
                 }
-                else if ((entryAsContainer = entry as IHtmlContentContainer) != null)
+                else if (entry is IHtmlContentContainer entryAsContainer)
                 {
                     // Since we're moving, do a deep flatten.
                     entryAsContainer.MoveTo(destination);
@@ -197,11 +195,9 @@ namespace Microsoft.AspNetCore.Html
 
         private string DebuggerToString()
         {
-            using (var writer = new StringWriter())
+            using var writer = new StringWriter();
-            {
+            WriteTo(writer, HtmlEncoder.Default);
-                WriteTo(writer, HtmlEncoder.Default);
+            return writer.ToString();
-                return writer.ToString();
-            }
         }
     }
 }

src/Html/Abstractions/src/HtmlFormattableString.cs

@@ -1,4 +1,4 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
@@ -39,7 +39,7 @@ namespace Microsoft.AspNetCore.Html
         /// <param name="formatProvider">An object that provides culture-specific formatting information.</param>
         /// <param name="format">A composite format string.</param>
         /// <param name="args">An array that contains objects to format.</param>
-        public HtmlFormattableString(IFormatProvider formatProvider, string format, params object[] args)
+        public HtmlFormattableString(IFormatProvider? formatProvider, string format, params object[] args)
         {
             if (format == null)
             {
@@ -94,7 +94,7 @@ namespace Microsoft.AspNetCore.Html
             private readonly HtmlEncoder _encoder;
             private readonly IFormatProvider _formatProvider;
 
-            private StringWriter _writer;
+            private StringWriter? _writer;
 
             public EncodingFormatProvider(IFormatProvider formatProvider, HtmlEncoder encoder)
             {
@@ -105,7 +105,7 @@ namespace Microsoft.AspNetCore.Html
                 _encoder = encoder;
             }
 
-            public string Format(string format, object arg, IFormatProvider formatProvider)
+            public string Format(string? format, object? arg, IFormatProvider? formatProvider)
             {
                 // These are the cases we need to special case. We trust the HtmlString or IHtmlContent instance
                 // to do the right thing with encoding.
@@ -118,7 +118,7 @@ namespace Microsoft.AspNetCore.Html
                 var htmlContent = arg as IHtmlContent;
                 if (htmlContent != null)
                 {
-                    _writer = _writer ?? new StringWriter();
+                    _writer ??= new StringWriter();
 
                     htmlContent.WriteTo(_writer, _encoder);
 
@@ -133,7 +133,7 @@ namespace Microsoft.AspNetCore.Html
                 //
                 // First check for an ICustomFormatter - if the IFormatProvider is a CultureInfo, then it's likely
                 // that ICustomFormatter will be null.
-                var customFormatter = (ICustomFormatter)_formatProvider.GetFormat(typeof(ICustomFormatter));
+                var customFormatter = (ICustomFormatter?)_formatProvider.GetFormat(typeof(ICustomFormatter));
                 if (customFormatter != null)
                 {
                     var result = customFormatter.Format(format, arg, _formatProvider);
@@ -170,7 +170,7 @@ namespace Microsoft.AspNetCore.Html
                 return string.Empty;
             }
 
-            public object GetFormat(Type formatType)
+            public object? GetFormat(Type? formatType)
             {
                 if (formatType == typeof(ICustomFormatter))
                 {

src/Html/Abstractions/src/HtmlString.cs

@@ -26,7 +26,7 @@ namespace Microsoft.AspNetCore.Html
         /// Creates a new <see cref="HtmlString"/>.
         /// </summary>
         /// <param name="value">The HTML encoded value.</param>
-        public HtmlString(string value)
+        public HtmlString(string? value)
         {
             Value = value;
         }
@@ -34,7 +34,7 @@ namespace Microsoft.AspNetCore.Html
         /// <summary>
         /// Gets the HTML encoded value.
         /// </summary>
-        public string Value { get; }
+        public string? Value { get; }
 
         /// <inheritdoc />
         public void WriteTo(TextWriter writer, HtmlEncoder encoder)

src/Html/Abstractions/src/Microsoft.AspNetCore.Html.Abstractions.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <Description>ASP.NET Core HTML abstractions used for building HTML content.
@@ -11,6 +11,7 @@ Microsoft.AspNetCore.Html.IHtmlContent</Description>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <PackageTags>aspnetcore</PackageTags>
     <IsPackable>false</IsPackable>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
 </Project>

src/Html/Abstractions/test/HtmlContentBuilderTest.cs

@@ -256,7 +256,7 @@ namespace Microsoft.Extensions.Internal
                 return _content.GetHashCode();
             }
 
-            public override bool Equals(object obj)
+            public override bool Equals(object? obj)
             {
                 var other = obj as TestHtmlContent;
                 if (other != null)
@@ -267,9 +267,9 @@ namespace Microsoft.Extensions.Internal
                 return base.Equals(obj);
             }
 
-            public bool Equals(TestHtmlContent other)
+            public bool Equals(TestHtmlContent? other)
             {
-                return string.Equals(_content, other._content);
+                return other != null && string.Equals(_content, other._content);
             }
         }
     }

src/Html/Abstractions/test/Microsoft.AspNetCore.Html.Abstractions.Tests.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>$(DefaultNetCoreTargetFramework)</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>