[Xamarin.Android.Build.Tasks] use copilot to opt into NRT

.github/copilot-instructions.md

@@ -0,0 +1,107 @@
+# Instructions for AIs
+
+This repository is .NET for Android.
+
+This is the main branch targeting .NET 10.
+
+## Nullable Reference Types
+
+When opting C# code into nullable reference types:
+
+* Add `#nullable enable` at the top of the file.
+
+* Don't *ever* use `!` to handle `null`!
+
+* Declare variables non-nullable, and check for `null` at entry points.
+
+* Use `throw new ArgumentNullException (nameof (parameter))` in `netstandard2.0` projects.
+
+* Use `ArgumentNullException.ThrowIfNull (parameter)` in Android projects that will be .NET 10+.
+
+* `[Required]` properties in MSBuild task classes should always be non-nullable with a default value.
+
+* Non-`[Required]` properties should be nullable and have null-checks in C# code using them.
+
+* For MSBuild task properties like:
+
+```csharp
+public string NonRequiredProperty { get; set; }
+public ITaskItem [] NonRequiredItemGroup { get; set; }
+
+[Output]
+public string OutputProperty { get; set; }
+[Output]
+public ITaskItem [] OutputItemGroup { get; set; }
+
+[Required]
+public string RequiredProperty { get; set; }
+[Required]
+public ITaskItem [] RequiredItemGroup { get; set; }
+```
+
+Fix them such as:
+
+```csharp
+public string? NonRequiredProperty { get; set; }
+public ITaskItem []? NonRequiredItemGroup { get; set; }
+
+[Output]
+public string? OutputProperty { get; set; }
+[Output]
+public ITaskItem []? OutputItemGroup { get; set; }
+
+[Required]
+public string RequiredProperty { get; set; } = "";
+[Required]
+public ITaskItem [] RequiredItemGroup { get; set; } = [];
+```
+
+If you see a `string.IsNullOrEmpty()` check:
+
+```csharp
+if (!string.IsNullOrEmpty (NonRequiredProperty)) {
+    // Code here
+}
+```
+
+Convert this to:
+
+```csharp
+if (NonRequiredProperty is { Length: > 0 }) {
+    // Code here
+}
+```
+
+## Formatting
+
+C# code uses tabs (not spaces) and the Mono code-formatting style defined in `.editorconfig`
+
+* Your mission is to make diffs as absolutely as small as possible, preserving existing code formatting.
+
+* If you encounter additional spaces or formatting within existing code blocks, LEAVE THEM AS-IS.
+
+* If you encounter code comments, LEAVE THEM AS-IS.
+
+* Place a space prior to any parentheses `(` or `[`
+
+* Use `""` for empty string and *not* `string.Empty`
+
+* Use `[]` for empty arrays and *not* `Array.Empty<T>()`
+
+Examples of properly formatted code:
+
+```csharp
+Foo ();
+Bar (1, 2, "test");
+myarray [0] = 1;
+
+if (someValue) {
+    // Code here
+}
+
+try {
+    // Code here
+} catch (Exception e) {
+    // Code here
+}
+```

src/Xamarin.Android.Build.Tasks/Tasks/D8.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 using System.Collections.Generic;
@@ -15,32 +17,32 @@ public class D8 : JavaToolTask
 		public override string TaskPrefix => "DX8";
 
 		[Required]
-		public string JarPath { get; set; }
+		public string JarPath { get; set; } = "";
 
 		/// <summary>
 		/// Output for *.dex files. R8 can be invoked for just --main-dex-list-output, so this is not [Required]
 		/// </summary>
-		public string OutputDirectory { get; set; }
+		public string? OutputDirectory { get; set; }
 
 		/// <summary>
 		/// It is loaded to calculate --min-api, which is used by desugaring part to determine which levels of desugaring it performs.
 		/// </summary>
-		public string AndroidManifestFile { get; set; }
+		public string? AndroidManifestFile { get; set; }
 
 		// general d8 feature options.
 		public bool Debug { get; set; }
 		public bool EnableDesugar { get; set; } = true;
 
 		// Java libraries to embed or reference
-		public string ClassesZip { get; set; }
+		public string? ClassesZip { get; set; }
 		[Required]
-		public string JavaPlatformJarPath { get; set; }
-		public ITaskItem [] JavaLibrariesToEmbed { get; set; }
-		public ITaskItem [] AlternativeJarLibrariesToEmbed { get; set; }
-		public ITaskItem [] JavaLibrariesToReference { get; set; }
-		public ITaskItem [] MapDiagnostics { get; set; }
+		public string JavaPlatformJarPath { get; set; } = "";
+		public ITaskItem []? JavaLibrariesToEmbed { get; set; }
+		public ITaskItem []? AlternativeJarLibrariesToEmbed { get; set; }
+		public ITaskItem []? JavaLibrariesToReference { get; set; }
+		public ITaskItem []? MapDiagnostics { get; set; }
 
-		public string ExtraArguments { get; set; }
+		public string? ExtraArguments { get; set; }
 
 		protected override string GenerateCommandLineCommands ()
 		{
@@ -55,22 +57,22 @@ protected virtual CommandLineBuilder GetCommandLineBuilder ()
 		{
 			var cmd = new CommandLineBuilder ();
 
-			if (!string.IsNullOrEmpty (JavaOptions)) {
+			if (JavaOptions is { Length: > 0 }) {
 				cmd.AppendSwitch (JavaOptions);
 			}
 			cmd.AppendSwitchIfNotNull ("-Xmx", JavaMaximumHeapSize);
 			cmd.AppendSwitchIfNotNull ("-classpath ", JarPath);
 			cmd.AppendSwitch (MainClass);
 
-			if (!string.IsNullOrEmpty (ExtraArguments))
+			if (ExtraArguments is { Length: > 0 })
 				cmd.AppendSwitch (ExtraArguments); // it should contain "--dex".
 			if (Debug)
 				cmd.AppendSwitch ("--debug");
 			else
 				cmd.AppendSwitch ("--release");
 
 			//NOTE: if this is blank, we can omit --min-api in this call
-			if (!string.IsNullOrEmpty (AndroidManifestFile)) {
+			if (AndroidManifestFile is { Length: > 0 }) {
 				var doc = AndroidAppManifest.Load (AndroidManifestFile, MonoAndroidHelper.SupportedVersions);
 				if (doc.MinSdkVersion.HasValue) {
 					MinSdkVersion = doc.MinSdkVersion.Value;
@@ -90,7 +92,7 @@ protected virtual CommandLineBuilder GetCommandLineBuilder ()
 				}
 			} else if (JavaLibrariesToEmbed != null) {
 				Log.LogDebugMessage ("  processing ClassesZip, JavaLibrariesToEmbed...");
-				if (!string.IsNullOrEmpty (ClassesZip) && File.Exists (ClassesZip)) {
+				if (ClassesZip is { Length: > 0 } && File.Exists (ClassesZip)) {
 					injars.Add (ClassesZip);
 				}
 				foreach (var jar in JavaLibrariesToEmbed) {
@@ -114,7 +116,7 @@ protected virtual CommandLineBuilder GetCommandLineBuilder ()
 				foreach (var diagnostic in MapDiagnostics) {
 					var from = diagnostic.ItemSpec;
 					var to = diagnostic.GetMetadata ("To");
-					if (string.IsNullOrEmpty (from) || string.IsNullOrEmpty (to))
+					if (from is not { Length: > 0 } || to is not { Length: > 0 })
 						continue;
 					cmd.AppendSwitch ("--map-diagnostics");
 					cmd.AppendSwitch (from);

src/Xamarin.Android.Build.Tasks/Tasks/R8.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 using System;
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
@@ -17,22 +19,22 @@ public class R8 : D8
 		public override string TaskPrefix => "R8S";
 
 		[Required]
-		public string AndroidSdkBuildToolsPath { get; set; }
+		public string AndroidSdkBuildToolsPath { get; set; } = "";
 
 		// multidex
 		public bool EnableMultiDex { get; set; }
-		public ITaskItem [] CustomMainDexListFiles { get; set; }
-		public string MultiDexMainDexListFile { get; set; }
+		public ITaskItem []? CustomMainDexListFiles { get; set; }
+		public string? MultiDexMainDexListFile { get; set; }
 
 		// proguard-like configuration settings
 		public bool EnableShrinking { get; set; } = true;
 		public bool IgnoreWarnings { get; set; }
-		public string AcwMapFile { get; set; }
-		public string ProguardGeneratedReferenceConfiguration { get; set; }
-		public string ProguardGeneratedApplicationConfiguration { get; set; }
-		public string ProguardCommonXamarinConfiguration { get; set; }
-		public string ProguardMappingFileOutput { get; set; }
-		public string [] ProguardConfigurationFiles { get; set; }
+		public string? AcwMapFile { get; set; }
+		public string? ProguardGeneratedReferenceConfiguration { get; set; }
+		public string? ProguardGeneratedApplicationConfiguration { get; set; }
+		public string? ProguardCommonXamarinConfiguration { get; set; }
+		public string? ProguardMappingFileOutput { get; set; }
+		public string []? ProguardConfigurationFiles { get; set; }
 
 		protected override string MainClass => "com.android.tools.r8.R8";
 

src/Xamarin.Android.Build.Tasks/Tasks/ResolveAndroidTooling.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 using Microsoft.Build.Framework;
 using Microsoft.Build.Utilities;
 using System;
@@ -20,54 +22,54 @@ public class ResolveAndroidTooling : AndroidTask
 	{
 		public override string TaskPrefix => "RAT";
 
-		public string TargetPlatformVersion { get; set; }
+		public string? TargetPlatformVersion { get; set; }
 
-		public string AndroidSdkPath { get; set; }
+		public string? AndroidSdkPath { get; set; }
 
-		public string AndroidSdkBuildToolsVersion { get; set; }
+		public string? AndroidSdkBuildToolsVersion { get; set; }
 
-		public string CommandLineToolsVersion { get; set; }
+		public string? CommandLineToolsVersion { get; set; }
 
-		public string ProjectFilePath { get; set; }
+		public string? ProjectFilePath { get; set; }
 
-		public string SequencePointsMode { get; set; }
+		public string? SequencePointsMode { get; set; }
 
 		public bool AotAssemblies { get; set; }
 
 		public bool AndroidApplication { get; set; } = true;
 
 		[Output]
-		public string AndroidApiLevel { get; set; }
+		public string? AndroidApiLevel { get; set; }
 
 		[Output]
-		public string AndroidApiLevelName { get; set; }
+		public string? AndroidApiLevelName { get; set; }
 
 		[Output]
-		public string AndroidSdkBuildToolsPath { get; set; }
+		public string? AndroidSdkBuildToolsPath { get; set; }
 
 		[Output]
-		public string AndroidSdkBuildToolsBinPath { get; set; }
+		public string? AndroidSdkBuildToolsBinPath { get; set; }
 
 		[Output]
-		public string ZipAlignPath { get; set; }
+		public string? ZipAlignPath { get; set; }
 
 		[Output]
-		public string AndroidSequencePointsMode { get; set; }
+		public string? AndroidSequencePointsMode { get; set; }
 
 		[Output]
-		public string LintToolPath { get; set; }
+		public string? LintToolPath { get; set; }
 
 		[Output]
-		public string ApkSignerJar { get; set; }
+		public string? ApkSignerJar { get; set; }
 
 		[Output]
 		public bool AndroidUseApkSigner { get; set; }
 
 		[Output]
-		public string Aapt2Version { get; set; }
+		public string? Aapt2Version { get; set; }
 
 		[Output]
-		public string Aapt2ToolPath { get; set; }
+		public string? Aapt2ToolPath { get; set; }
 
 		protected static readonly bool IsWindows = Path.DirectorySeparatorChar == '\\';
 		protected static readonly string ZipAlign = IsWindows ? "zipalign.exe" : "zipalign";
@@ -88,7 +90,7 @@ public override bool RunTask ()
 			string toolsZipAlignPath = Path.Combine (AndroidSdkPath, "tools", ZipAlign);
 			bool findZipAlign = (string.IsNullOrEmpty (ZipAlignPath) || !Directory.Exists (ZipAlignPath)) && !File.Exists (toolsZipAlignPath);
 
-			var lintPaths = MonoAndroidHelper.AndroidSdk.GetCommandLineToolsPaths (CommandLineToolsVersion)
+			var lintPaths = MonoAndroidHelper.AndroidSdk.GetCommandLineToolsPaths (CommandLineToolsVersion ?? "")
 				.SelectMany (p => new[]{
 					p,
 					Path.Combine (p, "bin"),
@@ -102,7 +104,7 @@ public override bool RunTask ()
 				}
 			}
 
-			foreach (var dir in MonoAndroidHelper.AndroidSdk.GetBuildToolsPaths (AndroidSdkBuildToolsVersion)) {
+			foreach (var dir in MonoAndroidHelper.AndroidSdk.GetBuildToolsPaths (AndroidSdkBuildToolsVersion ?? "")) {
 				Log.LogDebugMessage ("Trying build-tools path: {0}", dir);
 				if (dir == null || !Directory.Exists (dir))
 					continue;
@@ -222,7 +224,7 @@ bool GetAapt2Version (string aapt2Exe)
 			// because the path to aapt2 is in the key and the value is a string.
 			var key = ($"{nameof (ResolveAndroidTooling)}.{nameof (Aapt2Version)}", aapt2Tool);
 			var cached = BuildEngine4.GetRegisteredTaskObject (key, RegisteredTaskObjectLifetime.AppDomain) as string;
-			if (!string.IsNullOrEmpty (cached)) {
+			if (cached is { Length: > 0 }) {
 				Log.LogDebugMessage ($"Using cached value for {nameof (Aapt2Version)}: {cached}");
 				Aapt2Version = cached;
 				return true;
@@ -254,7 +256,10 @@ bool GetAapt2Version (string aapt2Exe)
 
 		protected int GetMaxStableApiLevel ()
 		{
-			return MonoAndroidHelper.SupportedVersions.MaxStableVersion.ApiLevel;
+			var stableVersion = MonoAndroidHelper.SupportedVersions.MaxStableVersion;
+			if (stableVersion is null)
+				throw new ArgumentNullException ("MaxStableVersion");
+			return stableVersion.ApiLevel;
 		}
 	}
 }