[Build] Enable nullable feature

Author: Kryptos-FR

src/Markdig.Wpf.SampleApp/Markdig.Wpf.SampleApp.csproj

@@ -9,6 +9,7 @@
     <AnalysisLevel>latest</AnalysisLevel>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <LangVersion>9</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
   <ItemGroup>
     <EmbeddedResource Update="Properties\Resources.resx" Generator="ResXFileCodeGenerator" LastGenOutput="Resources.Designer.cs" />

src/Markdig.Wpf.SampleAppCustomized/Customized/LinkInlineRenderer.cs

@@ -1,4 +1,6 @@
-using Markdig.Syntax.Inlines;
+using System;
+
+using Markdig.Syntax.Inlines;
 
 namespace Markdig.Wpf.SampleAppCustomized.Customized
 {
@@ -13,7 +15,7 @@ public LinkInlineRenderer(string linkpath)
 
         protected override void Write(Renderers.WpfRenderer renderer, LinkInline link)
         {
-            if (link.IsImage)
+            if (link?.IsImage ?? throw new ArgumentNullException(nameof(link)))
                 link.Url = _linkpath + link.Url;
 
             base.Write(renderer, link);

src/Markdig.Wpf.SampleAppCustomized/Markdig.Wpf.SampleAppCustomized.csproj

@@ -9,6 +9,7 @@
     <AnalysisLevel>latest</AnalysisLevel>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <LangVersion>9</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
   <ItemGroup>
     <EmbeddedResource Update="Properties\Resources.resx" Generator="ResXFileCodeGenerator" LastGenOutput="Resources.Designer.cs" />

src/Markdig.Wpf/Annotations/CanBeNullAttribute.cs

@@ -28,6 +28,7 @@
     <AnalysisLevel>latest</AnalysisLevel>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <LangVersion>9</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(SignAssembly)' == 'true' ">
     <AssemblyOriginatorKeyFile>key.snk</AssemblyOriginatorKeyFile>

src/Markdig.Wpf/Annotations/NotNullAttribute.cs

@@ -5,7 +5,6 @@
 using System;
 using System.IO;
 using System.Windows.Documents;
-using Markdig.Annotations;
 using Markdig.Renderers;
 using Markdig.Syntax;
 
@@ -23,8 +22,7 @@ public static partial class Markdown
         /// <param name="pipeline">The pipeline used for the conversion.</param>
         /// <returns>The result of the conversion</returns>
         /// <exception cref="System.ArgumentNullException">if markdown variable is null</exception>
-        [NotNull]
-        public static FlowDocument ToFlowDocument([NotNull] string markdown, MarkdownPipeline pipeline = null, WpfRenderer renderer = null)
+        public static FlowDocument ToFlowDocument(string markdown, MarkdownPipeline? pipeline = null, WpfRenderer? renderer = null)
         {
             if (markdown == null) throw new ArgumentNullException(nameof(markdown));
             pipeline = pipeline ?? new MarkdownPipelineBuilder().Build();
@@ -52,8 +50,7 @@ public static FlowDocument ToFlowDocument([NotNull] string markdown, MarkdownPip
         /// <param name="pipeline">The pipeline used for the conversion.</param>
         /// <returns>The result of the conversion</returns>
         /// <exception cref="ArgumentNullException">if markdown variable is null</exception>
-        [NotNull]
-        public static string ToXaml([NotNull] string markdown, [CanBeNull] MarkdownPipeline pipeline = null)
+        public static string ToXaml(string markdown, MarkdownPipeline? pipeline = null)
         {
             if (markdown == null) throw new ArgumentNullException(nameof(markdown));
             using (var writer = new StringWriter())
@@ -71,8 +68,7 @@ public static string ToXaml([NotNull] string markdown, [CanBeNull] MarkdownPipel
         /// <param name="pipeline">The pipeline used for the conversion.</param>
         /// <returns>The Markdown document that has been parsed</returns>
         /// <exception cref="ArgumentNullException">if reader or writer variable are null</exception>
-        public static MarkdownDocument ToXaml([NotNull] string markdown, [NotNull] TextWriter writer,
-            [CanBeNull] MarkdownPipeline pipeline = null)
+        public static MarkdownDocument ToXaml(string markdown, TextWriter writer, MarkdownPipeline? pipeline = null)
         {
             if (markdown == null) throw new ArgumentNullException(nameof(markdown));
             if (writer == null) throw new ArgumentNullException(nameof(writer));

src/Markdig.Wpf/Markdig.Wpf.csproj

@@ -3,7 +3,6 @@
 // See the LICENSE.md file in the project root for more information.
 
 using System;
-using Markdig.Annotations;
 
 // ReSharper disable once CheckNamespace
 namespace Markdig.Wpf
@@ -18,7 +17,7 @@ public static class MarkdownExtensions
         /// </summary>
         /// <param name="pipeline">The pipeline.</param>
         /// <returns>The modified pipeline</returns>
-        public static MarkdownPipelineBuilder UseSupportedExtensions([NotNull] this MarkdownPipelineBuilder pipeline)
+        public static MarkdownPipelineBuilder UseSupportedExtensions(this MarkdownPipelineBuilder pipeline)
         {
             if (pipeline == null) throw new ArgumentNullException(nameof(pipeline));
             return pipeline

src/Markdig.Wpf/Markdown.cs

@@ -43,7 +43,7 @@ static MarkdownViewer()
         /// <summary>
         /// Gets the flow document to display.
         /// </summary>
-        public FlowDocument Document
+        public FlowDocument? Document
         {
             get { return (FlowDocument)GetValue(DocumentProperty); }
             protected set { SetValue(DocumentPropertyKey, value); }
@@ -52,7 +52,7 @@ public FlowDocument Document
         /// <summary>
         /// Gets or sets the markdown to display.
         /// </summary>
-        public string Markdown
+        public string? Markdown
         {
             get { return (string)GetValue(MarkdownProperty); }
             set { SetValue(MarkdownProperty, value); }

src/Markdig.Wpf/MarkdownExtensions.cs

@@ -2,20 +2,21 @@
 // This file is licensed under the MIT license. 
 // See the LICENSE.md file in the project root for more information.
 
+using System;
 using System.Windows;
 using System.Windows.Documents;
-using Markdig.Annotations;
 using Markdig.Syntax;
 using Markdig.Wpf;
 
 namespace Markdig.Renderers.Wpf
 {
     public class CodeBlockRenderer : WpfObjectRenderer<CodeBlock>
     {
-        protected override void Write([NotNull] WpfRenderer renderer, [NotNull] CodeBlock obj)
+        protected override void Write(WpfRenderer renderer, CodeBlock obj)
         {
-            var paragraph = new Paragraph();
+            if (renderer == null) throw new ArgumentNullException(nameof(renderer));
 
+            var paragraph = new Paragraph();
             paragraph.SetResourceReference(FrameworkContentElement.StyleProperty, Styles.CodeBlockStyleKey);
             renderer.Push(paragraph);
             renderer.WriteLeafRawLines(obj);