feat: support C# 8 and nullable reference types (#245)

.editorconfig

@@ -18,32 +18,32 @@ indent_size = 2
 indent_size                                                            = 4
 
 # Style I care about
-csharp_style_expression_bodied_constructors                            = false : error
-csharp_prefer_braces                                                   = true : error
-dotnet_sort_system_directives_first                                    = true : error
+csharp_style_expression_bodied_constructors                            = false
+csharp_prefer_braces                                                   = true
+dotnet_sort_system_directives_first                                    = true
 
 # Stuff that is usually best
-csharp_style_inlined_variable_declaration                              = true : warning
-csharp_style_var_elsewhere                                             = true : warning
-csharp_space_after_cast                                                = true : warning
-csharp_style_pattern_matching_over_as_with_null_check                  = true : warning
-csharp_style_pattern_matching_over_is_with_cast_check                  = true : warning
-csharp_style_var_for_built_in_types                                    = true : warning
-csharp_style_var_when_type_is_apparent                                 = true : warning
-csharp_new_line_before_catch                                           = true : warning
-csharp_new_line_before_else                                            = true : warning
-csharp_new_line_before_finally                                         = true : warning
-csharp_indent_case_contents                                            = true : warning
+csharp_style_inlined_variable_declaration                              = true
+csharp_style_var_elsewhere                                             = true
+csharp_space_after_cast                                                = true
+csharp_style_pattern_matching_over_as_with_null_check                  = true
+csharp_style_pattern_matching_over_is_with_cast_check                  = true
+csharp_style_var_for_built_in_types                                    = true
+csharp_style_var_when_type_is_apparent                                 = true
+csharp_new_line_before_catch                                           = true
+csharp_new_line_before_else                                            = true
+csharp_new_line_before_finally                                         = true
+csharp_indent_case_contents                                            = true
 csharp_new_line_before_open_brace                                      = all
-csharp_indent_switch_labels                                            = true : warning
+csharp_indent_switch_labels                                            = true
 csharp_indent_labels                                                   = one_less_than_current
-csharp_prefer_simple_default_expression                                = true : warning
+csharp_prefer_simple_default_expression                                = true
 
 # Good defaults, but not always
-dotnet_style_object_initializer                                        = true : suggestion
-csharp_style_expression_bodied_indexers                                = true : suggestion
-csharp_style_expression_bodied_accessors                               = true : suggestion
-csharp_style_throw_expression                                          = true : suggestion
+dotnet_style_object_initializer                                        = true
+csharp_style_expression_bodied_indexers                                = true
+csharp_style_expression_bodied_accessors                               = true
+csharp_style_throw_expression                                          = true
 
 # Naming styles
 

CommandLineUtils.sln

@@ -1,8 +1,8 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 15
-VisualStudioVersion = 15.0.27130.2026
-MinimumVisualStudioVersion = 15.0.26124.0
+# Visual Studio 16
+VisualStudioVersion = 16.0.0.0
+MinimumVisualStudioVersion = 16.0.0.0
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{95D4B35E-0A21-4D64-8BAF-27DD6C019FC5}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "McMaster.Extensions.CommandLineUtils", "src\CommandLineUtils\McMaster.Extensions.CommandLineUtils.csproj", "{CBCFAFF3-A3B1-4C41-B2D1-092BF7307A4E}"

Directory.Build.props

@@ -22,7 +22,10 @@
     <EmbedUntrackedSources>true</EmbedUntrackedSources>
     <PackageIconUrl>https://natemcmaster.github.io/CommandLineUtils/logo.png</PackageIconUrl>
     <NoPackageAnalysis>true</NoPackageAnalysis>
-    <LangVersion>7.2</LangVersion>
+    <LangVersion>8.0</LangVersion>
+    <Nullable>enable</Nullable>
+    <!-- Some previews of .NET Core 3 don't have the rename yet -->
+    <NullableContextOptions>enable</NullableContextOptions>
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)src\StrongName.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
     <AzureKeyVaultUrl>https://nmcmaster.vault.azure.net</AzureKeyVaultUrl>
@@ -31,7 +34,7 @@
     <CodeSignCertName>DigiCertCodeSign</CodeSignCertName>
 
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-    <GenerateFullPaths Condition="'$(VSCODE_CWD)' != ''">true</GenerateFullPaths>
+    <GenerateFullPaths Condition="'$(TERM_PROGRAM)' == 'vscode'">true</GenerateFullPaths>
     <BaseIntermediateOutputPath>$(MSBuildThisFileDirectory).build\obj\$(MSBuildProjectName)\</BaseIntermediateOutputPath>
     <BaseOutputPath>$(MSBuildThisFileDirectory).build\bin\$(MSBuildProjectName)\</BaseOutputPath>
   </PropertyGroup>

azure-pipelines.yml

@@ -16,12 +16,19 @@ variables:
 jobs:
 - job: Windows
   pool:
-    vmImage: vs2017-win2016
+    vmImage: windows-2019
   steps:
-  - task: DotNetCoreInstaller@0
-    displayName: Install .NET Core 2.2
+  - task: UseDotNet@2
+    displayName: Install .NET Core 3 SDK
     inputs:
-      version: '2.2.102'
+      version: '3.x'
+      packageType: sdk
+      includePreviewVersions: true
+  - task: UseDotNet@2
+    displayName: Install .NET Core 2.2 runtime
+    inputs:
+      version: '2.2.x'
+      packageType: runtime
   - powershell: ./build.ps1 -ci
     displayName: Invoke build.ps1
     condition: eq(variables['kv-access-token'], '')
@@ -47,10 +54,17 @@ jobs:
   pool:
     vmImage: 'Ubuntu-16.04'
   steps:
-  - task: DotNetCoreInstaller@0
-    displayName: Install .NET Core 2.2
+  - task: UseDotNet@2
+    displayName: Install .NET Core 3 SDK
+    inputs:
+      version: '3.x'
+      packageType: sdk
+      includePreviewVersions: true
+  - task: UseDotNet@2
+    displayName: Install .NET Core 2.2 runtime
     inputs:
-      version: '2.2.102'
+      version: '2.2.x'
+      packageType: runtime
   - script: ./build.ps1 -ci
     displayName: Invoke build.ps1
   - task: PublishTestResults@2

docs/generate.ps1

@@ -24,7 +24,7 @@ try {
         exec git worktree add $targetDir gh-pages 2>&1 | out-null
     }
 
-    $docfxVersion = '2.40.5'
+    $docfxVersion = '2.43.1'
     $docfxRoot = "$buildRoot/packages/docfx.console/$docfxVersion"
     $docfx = "$docfxRoot/tools/docfx.exe"
     if (-not (Test-Path $docfx)) {

docs/samples/Directory.Build.props

@@ -0,0 +1,11 @@
+<Project>
+  <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory)..\, Directory.Build.props))\Directory.Build.props" />
+
+  <PropertyGroup>
+    <!-- Set samples to use the latest stable C# until C# 8 is released -->
+    <LangVersion>7.3</LangVersion>
+    <Nullable />
+    <NullableContextOptions />
+  </PropertyGroup>
+
+</Project>

src/CommandLineUtils/Abstractions/IValueParser.cs

@@ -24,6 +24,6 @@ public interface IValueParser
         /// <param name="culture">The culture that should be used to parse values.</param>
         /// <returns>The parsed value object.</returns>
         /// <throws name="System.FormatException">When the value cannot be parsed.</throws>
-        object Parse(string argName, string value, CultureInfo culture);
+        object? Parse(string? argName, string? value, CultureInfo culture);
     }
 }

src/CommandLineUtils/Abstractions/IValueParser{T}.cs

@@ -18,6 +18,6 @@ public interface IValueParser<T> : IValueParser
         /// <param name="culture">The culture that should be used to parse values.</param>
         /// <returns>The parsed value object.</returns>
         /// <throws name="System.FormatException">When the value cannot be parsed.</throws>
-        new T Parse(string argName, string value, CultureInfo culture);
+        new T Parse(string? argName, string? value, CultureInfo culture);
     }
 }

src/CommandLineUtils/Abstractions/ParseResult.cs

@@ -1,13 +1,37 @@
 // Copyright (c) Nate McMaster.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
+using System.ComponentModel;
+
 namespace McMaster.Extensions.CommandLineUtils.Abstractions
 {
     /// <summary>
     /// The result of parsing command line arguments.
     /// </summary>
     public class ParseResult
     {
+        /// <summary>
+        /// Initializes <see cref="ParseResult"/>.
+        /// </summary>
+        /// <param name="selectedCommand">The command selected for execution.</param>
+        public ParseResult(CommandLineApplication selectedCommand)
+        {
+            SelectedCommand = selectedCommand ?? throw new ArgumentNullException(nameof(selectedCommand));
+        }
+
+#pragma warning disable CS8618 // Non-nullable field is uninitialized.
+        /// <summary>
+        /// This constructor is obsolete and will be removed in a future version.
+        /// The recommended replacement is <see cref="ParseResult(CommandLineApplication)" />
+        /// </summary>
+        [Obsolete("This constructor is obsolete and will be removed in a future version. The recommended replacement is ctor(CommandLineApplication selectedCommand)")]
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public ParseResult()
+        {
+        }
+#pragma warning restore CS8618 // Non-nullable field is uninitialized.
+
         /// <summary>
         /// The application or subcommand that matches the command line arguments.
         /// </summary>

src/CommandLineUtils/Abstractions/ValueParserProvider.cs

@@ -71,7 +71,7 @@ public IValueParser GetParser(Type type)
         /// </remarks>
         /// <typeparam name="T"></typeparam>
         /// <returns></returns>
-        public IValueParser<T> GetParser<T>()
+        public IValueParser<T>? GetParser<T>()
         {
             var parser = GetParserImpl<T>();
             if (parser == null)
@@ -87,7 +87,7 @@ public IValueParser<T> GetParser<T>()
             return new GenericParserAdapter<T>(parser);
         }
 
-        internal IValueParser GetParserImpl<T>()
+        internal IValueParser? GetParserImpl<T>()
         {
             var type = typeof(T);
             if (_parsers.TryGetValue(type, out var parser))
@@ -102,7 +102,7 @@ internal IValueParser GetParserImpl<T>()
                 return EnumParser.Create(type);
             }
 
-            if (ReflectionHelper.IsNullableType(typeInfo, out var wrappedType))
+            if (ReflectionHelper.IsNullableType(typeInfo, out var wrappedType) && wrappedType != null)
             {
                 if (wrappedType.GetTypeInfo().IsEnum)
                 {
@@ -187,7 +187,7 @@ private void SafeAdd(IValueParser parser, bool andReplace = false)
                 throw new ArgumentNullException(nameof(parser));
             }
 
-            var targetType = parser.TargetType;
+            Type targetType = parser.TargetType;
 
             if (targetType == null)
             {
@@ -197,7 +197,7 @@ private void SafeAdd(IValueParser parser, bool andReplace = false)
             }
 
             // strip nullable wrappers since we have a dedicated nullable value parser
-            targetType = ReflectionHelper.IsNullableType(targetType.GetTypeInfo(), out var wrappedType)
+            targetType = ReflectionHelper.IsNullableType(targetType.GetTypeInfo(), out var wrappedType) && wrappedType != null
                 ? wrappedType
                 : targetType;
 
@@ -219,7 +219,7 @@ private void SafeAdd(IValueParser parser, bool andReplace = false)
 
         private sealed class GenericParserAdapter<T> : IValueParser<T>
         {
-            private IValueParser _inner;
+            private readonly IValueParser _inner;
 
             public GenericParserAdapter(IValueParser inner)
             {
@@ -228,9 +228,9 @@ public GenericParserAdapter(IValueParser inner)
 
             public Type TargetType => _inner.TargetType;
 
-            public T Parse(string argName, string value, CultureInfo culture) => (T)_inner.Parse(argName, value, culture);
+            public T Parse(string? argName, string? value, CultureInfo culture) => (T)_inner.Parse(argName, value, culture)!;
 
-            object IValueParser.Parse(string argName, string value, CultureInfo culture) => _inner.Parse(argName, value, culture);
+            object? IValueParser.Parse(string? argName, string? value, CultureInfo culture) => _inner.Parse(argName, value, culture);
         }
     }
 }

src/CommandLineUtils/Attributes/ArgumentAttribute.cs

@@ -27,7 +27,7 @@ public ArgumentAttribute(int order)
         /// </summary>
         /// <param name="order">The order</param>
         /// <param name="name">The name</param>
-        public ArgumentAttribute(int order, string name)
+        public ArgumentAttribute(int order, string? name)
             : this(order, name, null)
         { }
 
@@ -37,7 +37,7 @@ public ArgumentAttribute(int order, string name)
         /// <param name="order">The order</param>
         /// <param name="name">The name</param>
         /// <param name="description">The description</param>
-        public ArgumentAttribute(int order, string name, string description)
+        public ArgumentAttribute(int order, string? name, string? description)
         {
             Order = order;
             Name = name;
@@ -52,7 +52,7 @@ public ArgumentAttribute(int order, string name, string description)
         /// <summary>
         /// The name of the argument. <seealso cref="CommandArgument.Name"/>.
         /// </summary>
-        public string Name { get; set; }
+        public string? Name { get; set; }
 
         /// <summary>
         /// Determines if the argument appears in the generated help-text.  <seealso cref="CommandArgument.ShowInHelpText"/>.
@@ -62,7 +62,7 @@ public ArgumentAttribute(int order, string name, string description)
         /// <summary>
         /// A description of the argument.  <seealso cref="CommandArgument.Description"/>.
         /// </summary>
-        public string Description { get; set; }
+        public string? Description { get; set; }
 
         internal CommandArgument Configure(PropertyInfo prop)
         {

src/CommandLineUtils/Attributes/CommandAttribute.cs

@@ -44,10 +44,20 @@ public CommandAttribute(params string[] names)
         /// The name of the command line application. When this is a subcommand, it is the name of the word used to invoke the subcommand.
         /// <seealso cref="CommandLineApplication.Name" />
         /// </summary>
-        public string Name
+        public string? Name
         {
             get => _names.Length > 0 ? _names[0] : null;
-            set => _names = new[] { value };
+            set
+            {
+                if (value != null)
+                {
+                    _names = new[] { value };
+                }
+                else
+                {
+                    _names = Util.EmptyArray<string>();
+                }
+            }
         }
 
         /// <summary>
@@ -58,12 +68,12 @@ public string Name
         /// <summary>
         /// The full name of the command line application to show in help text. <seealso cref="CommandLineApplication.FullName" />
         /// </summary>
-        public string FullName { get; set; }
+        public string? FullName { get; set; }
 
         /// <summary>
         /// A description of the command. <seealso cref="CommandLineApplication.Description"/>
         /// </summary>
-        public string Description { get; set; }
+        public string? Description { get; set; }
 
         /// <summary>
         /// Determines if this command appears in generated help text. <seealso cref="CommandLineApplication.ShowInHelpText"/>
@@ -73,7 +83,7 @@ public string Name
         /// <summary>
         /// Additional text that appears at the bottom of generated help text. <seealso cref="CommandLineApplication.ExtendedHelpText"/>
         /// </summary>
-        public string ExtendedHelpText { get; set; }
+        public string? ExtendedHelpText { get; set; }
 
         /// <summary>
         /// Throw when unexpected arguments are encountered. <seealso cref="CommandLineApplication.ThrowOnUnexpectedArgument"/>

src/CommandLineUtils/Attributes/HelpOptionAttribute.cs

@@ -29,6 +29,11 @@ public HelpOptionAttribute(string template)
             Description = Strings.DefaultHelpOptionDescription;
         }
 
+        /// <summary>
+        /// The option template. This is parsed into the short and long name.
+        /// </summary>
+        public new string Template { get; set; }
+
         internal CommandOption Configure(CommandLineApplication app)
         {
             var opt = app.HelpOption(Template);

src/CommandLineUtils/Attributes/OptionAttribute.cs

@@ -53,7 +53,7 @@ public OptionAttribute(string template, CommandOptionType optionType)
         /// <param name="template">The template</param>
         /// <param name="description">The option description</param>
         /// <param name="optionType">The option type</param>
-        public OptionAttribute(string template, string description, CommandOptionType optionType)
+        public OptionAttribute(string? template, string? description, CommandOptionType optionType)
         {
             Template = template;
             Description = description;