Add NativeAOT test

NuGet.config

@@ -9,6 +9,8 @@
     <add key="dotnet-eng" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-eng/nuget/v3/index.json" />
     <add key="dotnet-tools" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-tools/nuget/v3/index.json" />
     <add key="dotnet-libraries" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-libraries/nuget/v3/index.json" />
+    <!-- required by NativeAOT -->
+    <add key="dotnet7" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet7/nuget/v3/index.json" />
   </packageSources>
   <disabledPackageSources />
 </configuration>

src/System.CommandLine.Tests/TrimmingTests.cs → src/System.CommandLine.Tests/CompilationTests.cs

@@ -8,17 +8,18 @@
 using System.IO;
 using System.Text;
 using FluentAssertions;
+using Microsoft.DotNet.PlatformAbstractions;
 using Xunit;
 using Xunit.Abstractions;
 
 namespace System.CommandLine.Tests;
 
-public class TrimmingTests
+public class CompilationTests
 {
     private readonly ITestOutputHelper _output;
     private readonly string _systemCommandLineDllPath;
 
-    public TrimmingTests(ITestOutputHelper output)
+    public CompilationTests(ITestOutputHelper output)
     {
         _output = output;
 
@@ -29,25 +30,35 @@ public TrimmingTests(ITestOutputHelper output)
     [InlineData("")]
     [InlineData("-p:PublishSingleFile=true")]
     public void App_referencing_system_commandline_can_be_trimmed(string additionalArgs)
+        => PublishAndValidate("Trimming", "warning IL", additionalArgs);
+
+    [ReleaseBuildOnlyFact]
+    public void App_referencing_system_commandline_can_be_compiled_ahead_of_time()
+        => PublishAndValidate("NativeAOT", "AOT analysis warning");
+
+    private void PublishAndValidate(string appName, string warningText, string additionalArgs = null)
     {
         var stdOut = new StringBuilder();
         var stdErr = new StringBuilder();
 
-        var workingDirectory = Path.Combine(Directory.GetCurrentDirectory(), "TrimmingTestApp");
-
+        var workingDirectory = Path.Combine(Directory.GetCurrentDirectory(), "TestApps", appName);
+
+        string rId = GetPortableRuntimeIdentifier();
+
         Process.RunToCompletion(
             DotnetMuxer.Path.FullName,
-            "clean -c Release -r win-x64",
+            $"clean -c Release -r {rId}",
             workingDirectory: workingDirectory);
 
-        var commandLine = string.Format(
-            "publish -c Release -r win-x64 --self-contained -p:SystemCommandLineDllPath=\"{0}\" -p:TreatWarningsAsErrors=true -p:PublishTrimmed=true {1}",
+        string publishCommand = string.Format(
+            "publish -c Release -r {0} --self-contained -p:SystemCommandLineDllPath=\"{1}\" -p:TreatWarningsAsErrors=true {2}",
+            rId,
             _systemCommandLineDllPath,
             additionalArgs);
 
         var exitCode = Process.RunToCompletion(
             DotnetMuxer.Path.FullName,
-            commandLine,
+            publishCommand,
             s =>
             {
                 _output.WriteLine(s);
@@ -60,10 +71,16 @@ public void App_referencing_system_commandline_can_be_trimmed(string additionalA
             },
             workingDirectory);
 
-        stdOut.ToString().Should().NotContain("warning IL");
+        stdOut.ToString().Should().NotContain(warningText);
         stdErr.ToString().Should().BeEmpty();
         exitCode.Should().Be(0);
     }
+
+    private static string GetPortableRuntimeIdentifier()
+    {
+        string osPart = OperatingSystem.IsWindows() ? "win" : (OperatingSystem.IsMacOS() ? "osx" : "linux");
+        return $"{osPart}-{RuntimeEnvironment.RuntimeArchitecture}";
+    }
 }
 
 #endif

src/System.CommandLine.Tests/System.CommandLine.Tests.csproj

@@ -14,16 +14,15 @@
     <EmbeddedResource Remove="TestResults\**" />
     <None Remove="TestResults\**" />
 
-    <Compile Remove="TrimmingTestApp/**" />
-    <Content Remove="TrimmingTestApp/**" />
-    <EmbeddedResource Remove="TrimmingTestApp/**" />
-    <None Remove="TrimmingTestApp/**" />
+    <Compile Remove="TestApps/**" />
+    <Content Remove="TestApps/**" />
+    <EmbeddedResource Remove="TestApps/**" />
+    <None Remove="TestApps/**" />
 
-
-    <Content Include="TrimmingTestApp/TrimmingTestApp.csproj">
+    <Content Include="TestApps/**/*.csproj">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
-    <Content Include="TrimmingTestApp/Program.cs">
+    <Content Include="TestApps/**/*.cs">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
 

src/System.CommandLine.Tests/TestApps/NativeAOT/NativeAOT.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+	<PropertyGroup>
+		<OutputType>Exe</OutputType>
+		<TargetFramework>net6.0</TargetFramework>
+		<!-- producing more detailed log output -->
+		<TrimmerSingleWarn>false</TrimmerSingleWarn>
+	</PropertyGroup>
+
+	<PropertyGroup>
+		<SystemCommandLineDllPath Condition="'$(SystemCommandLineDllPath)'==''">..\..\..\System.CommandLine\bin\Release\net6.0\System.CommandLine.dll</SystemCommandLineDllPath>
+	</PropertyGroup>
+
+	<ItemGroup>
+		<Reference Include="SystemCommandLineDll">
+			<HintPath>$(SystemCommandLineDllPath)</HintPath>
+		</Reference>
+		<PackageReference Include="Microsoft.DotNet.ILCompiler" Version="7.0.0-preview.3.22123.2" />
+	</ItemGroup>
+
+</Project>

src/System.CommandLine.Tests/TestApps/NativeAOT/Program.cs

@@ -0,0 +1,29 @@
+using System;
+using System.CommandLine;
+using System.CommandLine.Builder;
+using System.CommandLine.Parsing;
+
+public class Program
+{
+    static void Run(bool boolean, string text)
+    {
+        Console.WriteLine($"Bool option: {text}");
+        Console.WriteLine($"String option: {boolean}");
+    }
+
+    private static int Main(string[] args)
+    {
+        Option<bool> boolOption = new Option<bool>(new[] { "--bool", "-b" }, "Bool option");
+        Option<string> stringOption = new Option<string>(new[] { "--string", "-s" }, "String option");
+
+        RootCommand command = new RootCommand
+        {
+            boolOption,
+            stringOption
+        };
+
+        command.SetHandler<bool, string>(Run, boolOption, stringOption);
+
+        return new CommandLineBuilder(command).Build().Invoke(args);
+    }
+}

src/System.CommandLine.Tests/TrimmingTestApp/TrimmingTestApp.csproj → src/System.CommandLine.Tests/TestApps/Trimming/Trimming.csproj

@@ -10,7 +10,7 @@
 	</PropertyGroup>
 
 	<PropertyGroup>
-		<SystemCommandLineDllPath Condition="'$(SystemCommandLineDllPath)'==''">..\..\System.CommandLine\bin\Release\net6.0\System.CommandLine.dll</SystemCommandLineDllPath>
+		<SystemCommandLineDllPath Condition="'$(SystemCommandLineDllPath)'==''">..\..\..\System.CommandLine\bin\Release\net6.0\System.CommandLine.dll</SystemCommandLineDllPath>
 	</PropertyGroup>
 
 	<ItemGroup>

src/System.CommandLine/Binding/ArgumentConverter.DefaultValues.cs

@@ -15,7 +15,8 @@ internal static partial class ArgumentConverter
     private static ConstructorInfo? _listCtor;
 #endif
 
-    private static Array CreateEmptyArray(Type itemType, int capacity = 0)
+    [UnconditionalSuppressMessage("ReflectionAnalysis", "IL3050", Justification = "https://github.com/dotnet/command-line-api/issues/1638")]
+    private static Array CreateArray(Type itemType, int capacity)
         => Array.CreateInstance(itemType, capacity);
 
     private static IList CreateEmptyList(Type listType)
@@ -40,18 +41,18 @@ private static IList CreateEnumerable(Type type, Type itemType, int capacity = 0
     {
         if (type.IsArray)
         {
-            return CreateEmptyArray(itemType, capacity);
+            return CreateArray(itemType, capacity);
         }
 
         if (type.IsGenericType)
         {
             var x = type.GetGenericTypeDefinition() switch
             {
                 { } enumerable when typeof(IEnumerable<>).IsAssignableFrom(enumerable) =>
-                    CreateEmptyArray(itemType, capacity),
+                    CreateArray(itemType, capacity),
                 { } array when typeof(IList<>).IsAssignableFrom(array) ||
                                typeof(ICollection<>).IsAssignableFrom(array) =>
-                    CreateEmptyArray(itemType, capacity),
+                    CreateArray(itemType, capacity),
                 { } list when list == typeof(List<>) =>
                     CreateEmptyList(type),
                 _ => null

src/System.CommandLine/Binding/ArgumentConverter.cs

@@ -276,7 +276,7 @@ public static bool TryConvertArgument(ArgumentResult argumentResult, out object?
                     when nonGeneric == typeof(IList) ||
                          nonGeneric == typeof(ICollection) ||
                          nonGeneric == typeof(IEnumerable)
-                    => CreateEmptyArray(typeof(object)),
+                    => Array.Empty<object>(),
                 _ when type.IsValueType => CreateDefaultValueType(type),
                 _ => null
             };