Generate file-scoped namespace declarations, if possible.

ICSharpCode.Decompiler.Tests/Helpers/Tester.cs

@@ -549,9 +549,12 @@ namespace ICSharpCode.Decompiler.Tests.Helpers
 					CompilerOptions.UseRoslyn1_3_2 => CSharp.LanguageVersion.CSharp6,
 					CompilerOptions.UseRoslyn2_10_0 => CSharp.LanguageVersion.CSharp7_3,
 					CompilerOptions.UseRoslyn3_11_0 => CSharp.LanguageVersion.CSharp9_0,
-					_ => cscOptions.HasFlag(CompilerOptions.Preview) ? CSharp.LanguageVersion.Latest : CSharp.LanguageVersion.CSharp9_0,
+					_ => cscOptions.HasFlag(CompilerOptions.Preview) ? CSharp.LanguageVersion.Latest : CSharp.LanguageVersion.CSharp10_0,
+				};
+				return new DecompilerSettings(langVersion) {
+					// Never use file-scoped namespaces
+					FileScopedNamespaces = false
 				};
-				return new DecompilerSettings(langVersion);
 			}
 			else
 			{

ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj

@@ -108,6 +108,7 @@
     <Compile Include="TestCases\Correctness\DeconstructionTests.cs" />
     <Compile Include="TestCases\Correctness\DynamicTests.cs" />
     <Compile Include="TestCases\Correctness\StringConcat.cs" />
+    <None Include="TestCases\Pretty\FileScopedNamespaces.cs" />
     <Compile Include="TestCases\Pretty\PatternMatching.cs" />
     <None Include="TestCases\Ugly\NoPropertiesAndEvents.Expected.cs" />
     <Compile Include="TestCases\Ugly\NoPropertiesAndEvents.cs" />

ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs

@@ -113,13 +113,13 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void FSharpUsing_Debug()
 		{
-			Run(settings: new DecompilerSettings { RemoveDeadStores = true, UseEnhancedUsing = false });
+			Run(settings: new DecompilerSettings { RemoveDeadStores = true, UseEnhancedUsing = false, FileScopedNamespaces = false });
 		}
 
 		[Test]
 		public void FSharpUsing_Release()
 		{
-			Run(settings: new DecompilerSettings { RemoveDeadStores = true, UseEnhancedUsing = false });
+			Run(settings: new DecompilerSettings { RemoveDeadStores = true, UseEnhancedUsing = false, FileScopedNamespaces = false });
 		}
 
 		[Test]
@@ -137,13 +137,13 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void CS1xSwitch_Debug()
 		{
-			Run(settings: new DecompilerSettings { SwitchExpressions = false });
+			Run(settings: new DecompilerSettings { SwitchExpressions = false, FileScopedNamespaces = false });
 		}
 
 		[Test]
 		public void CS1xSwitch_Release()
 		{
-			Run(settings: new DecompilerSettings { SwitchExpressions = false });
+			Run(settings: new DecompilerSettings { SwitchExpressions = false, FileScopedNamespaces = false });
 		}
 
 		[Test]
@@ -240,14 +240,14 @@ namespace ICSharpCode.Decompiler.Tests
 		public void FSharpLoops_Debug()
 		{
 			CopyFSharpCoreDll();
-			Run(settings: new DecompilerSettings { RemoveDeadStores = true });
+			Run(settings: new DecompilerSettings { RemoveDeadStores = true, FileScopedNamespaces = false });
 		}
 
 		[Test]
 		public void FSharpLoops_Release()
 		{
 			CopyFSharpCoreDll();
-			Run(settings: new DecompilerSettings { RemoveDeadStores = true });
+			Run(settings: new DecompilerSettings { RemoveDeadStores = true, FileScopedNamespaces = false });
 		}
 
 		[Test]
@@ -259,6 +259,11 @@ namespace ICSharpCode.Decompiler.Tests
 		void Run([CallerMemberName] string testName = null, DecompilerSettings settings = null,
 			AssemblerOptions assemblerOptions = AssemblerOptions.Library)
 		{
+			if (settings == null)
+			{
+				// never use file-scoped namespaces, unless explicitly specified
+				settings = new DecompilerSettings { FileScopedNamespaces = false };
+			}
 			var ilFile = Path.Combine(TestCasePath, testName + ".il");
 			var csFile = Path.Combine(TestCasePath, testName + ".cs");
 

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -180,7 +180,8 @@ namespace ICSharpCode.Decompiler.Tests
 			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
 				NullPropagation = false,
 				// legacy csc generates a dead store in debug builds
-				RemoveDeadStores = (cscOptions == CompilerOptions.None)
+				RemoveDeadStores = (cscOptions == CompilerOptions.None),
+				FileScopedNamespaces = false,
 			});
 		}
 
@@ -191,6 +192,7 @@ namespace ICSharpCode.Decompiler.Tests
 				// legacy csc generates a dead store in debug builds
 				RemoveDeadStores = (cscOptions == CompilerOptions.None),
 				SwitchExpressions = false,
+				FileScopedNamespaces = false,
 			});
 		}
 
@@ -235,7 +237,10 @@ namespace ICSharpCode.Decompiler.Tests
 		{
 			RunForLibrary(
 				cscOptions: cscOptions,
-				decompilerSettings: new DecompilerSettings { UseEnhancedUsing = false }
+				decompilerSettings: new DecompilerSettings {
+					UseEnhancedUsing = false,
+					FileScopedNamespaces = false,
+				}
 			);
 		}
 
@@ -263,7 +268,8 @@ namespace ICSharpCode.Decompiler.Tests
 			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
 				// legacy csc generates a dead store in debug builds
 				RemoveDeadStores = (cscOptions == CompilerOptions.None),
-				UseExpressionBodyForCalculatedGetterOnlyProperties = false
+				UseExpressionBodyForCalculatedGetterOnlyProperties = false,
+				FileScopedNamespaces = false,
 			});
 		}
 
@@ -407,7 +413,7 @@ namespace ICSharpCode.Decompiler.Tests
 		{
 			RunForLibrary(
 				cscOptions: cscOptions,
-				decompilerSettings: new DecompilerSettings { UseEnhancedUsing = false }
+				decompilerSettings: new DecompilerSettings { UseEnhancedUsing = false, FileScopedNamespaces = false }
 			);
 		}
 
@@ -429,6 +435,12 @@ namespace ICSharpCode.Decompiler.Tests
 			RunForLibrary(cscOptions: cscOptions | CompilerOptions.Preview);
 		}
 
+		[Test]
+		public void FileScopedNamespaces([ValueSource(nameof(roslynLatestOnlyOptions))] CompilerOptions cscOptions)
+		{
+			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings());
+		}
+
 		[Test]
 		public void FunctionPointers([ValueSource(nameof(roslynLatestOnlyOptions))] CompilerOptions cscOptions)
 		{

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/ForLoopTests.xml

@@ -3,26 +3,25 @@
   <files>
     <file id="1" name="ICSharpCode\Decompiler\Tests\TestCases\PdbGen\ForLoopTests.cs" language="C#" checksumAlgorithm="SHA256"><![CDATA[using System;
 
-namespace ICSharpCode.Decompiler.Tests.TestCases.PdbGen
+namespace ICSharpCode.Decompiler.Tests.TestCases.PdbGen;
+
+public class ForLoopTests
 {
-	public class ForLoopTests
+	public static void SimplePrintLoop(string[] args)
 	{
-		public static void SimplePrintLoop(string[] args)
+		for (int i = 0; i < args.Length; i++)
 		{
-			for (int i = 0; i < args.Length; i++)
-			{
-				Console.WriteLine(args[i]);
-			}
+			Console.WriteLine(args[i]);
 		}
+	}
 
-		public static void SimplePrintLoopWithCondition(string[] args)
+	public static void SimplePrintLoopWithCondition(string[] args)
+	{
+		for (int i = 0; i < args.Length; i++)
 		{
-			for (int i = 0; i < args.Length; i++)
+			if (i % 2 != 0)
 			{
-				if (i % 2 != 0)
-				{
-					Console.WriteLine(args[i]);
-				}
+				Console.WriteLine(args[i]);
 			}
 		}
 	}

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/HelloWorld.xml

@@ -3,16 +3,15 @@
   <files>
     <file id="1" name="ICSharpCode\Decompiler\Tests\TestCases\PdbGen\HelloWorld.cs" language="C#" checksumAlgorithm="SHA256"><![CDATA[using System;
 
-namespace ICSharpCode.Decompiler.Tests.TestCases.PdbGen
+namespace ICSharpCode.Decompiler.Tests.TestCases.PdbGen;
+
+public class HelloWorld
 {
-	public class HelloWorld
+	public static void Main(string[] args)
 	{
-		public static void Main(string[] args)
-		{
-			Console.ReadKey();
-			Console.WriteLine("Hello World!");
-			Console.ReadKey();
-		}
+		Console.ReadKey();
+		Console.WriteLine("Hello World!");
+		Console.ReadKey();
 	}
 }
 ]]></file>

ICSharpCode.Decompiler.Tests/TestCases/PdbGen/LambdaCapturing.xml

@@ -3,21 +3,20 @@
   <files>
     <file id="1" name="ICSharpCode\Decompiler\Tests\TestCases\PdbGen\LambdaCapturing.cs" language="C#" checksumAlgorithm="SHA256"><![CDATA[using System;
 
-namespace ICSharpCode.Decompiler.Tests.TestCases.PdbGen
+namespace ICSharpCode.Decompiler.Tests.TestCases.PdbGen;
+
+public class LambdaCapturing
 {
-	public class LambdaCapturing
+	public static void Main(string[] args)
 	{
-		public static void Main(string[] args)
-		{
-			int num = 4;
-			int captured = Environment.TickCount + num;
-			Test((int a, int b) => a + b + captured);
-		}
+		int num = 4;
+		int captured = Environment.TickCount + num;
+		Test((int a, int b) => a + b + captured);
+	}
 
-		private static void Test(Func<int, int, int> p)
-		{
-			p(1, 2);
-		}
+	private static void Test(Func<int, int, int> p)
+	{
+		p(1, 2);
 	}
 }
 ]]></file>

ICSharpCode.Decompiler.Tests/TestCases/Pretty/FileScopedNamespaces.cs

@@ -0,0 +1,9 @@
+namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty;
+
+internal delegate void DelegateInFileScopedNamespace();
+
+internal class FileScopedNamespaces
+{
+
+}
+

ICSharpCode.Decompiler.Tests/UglyTestRunner.cs

@@ -74,7 +74,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void NoArrayInitializers([ValueSource(nameof(roslynOnlyOptions))] CompilerOptions cscOptions)
 		{
-			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
+			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings(CSharp.LanguageVersion.CSharp1) {
 				ArrayInitializers = false
 			});
 		}
@@ -82,7 +82,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void NoDecimalConstants([ValueSource(nameof(roslynOnlyOptions))] CompilerOptions cscOptions)
 		{
-			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
+			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings(CSharp.LanguageVersion.CSharp1) {
 				DecimalConstants = false
 			});
 		}
@@ -90,7 +90,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void NoExtensionMethods([ValueSource(nameof(roslynOnlyOptions))] CompilerOptions cscOptions)
 		{
-			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
+			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings(CSharp.LanguageVersion.CSharp9_0) {
 				ExtensionMethods = false
 			});
 		}
@@ -98,7 +98,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void NoForEachStatement([ValueSource(nameof(defaultOptions))] CompilerOptions cscOptions)
 		{
-			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
+			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings(CSharp.LanguageVersion.CSharp1) {
 				ForEachStatement = false,
 				UseEnhancedUsing = false,
 			});
@@ -113,7 +113,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void NoPropertiesAndEvents([ValueSource(nameof(defaultOptions))] CompilerOptions cscOptions)
 		{
-			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
+			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings(CSharp.LanguageVersion.CSharp1) {
 				AutomaticEvents = false,
 				AutomaticProperties = false,
 			});
@@ -122,7 +122,7 @@ namespace ICSharpCode.Decompiler.Tests
 		[Test]
 		public void AggressiveScalarReplacementOfAggregates([ValueSource(nameof(roslynOnlyOptions))] CompilerOptions cscOptions)
 		{
-			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings {
+			RunForLibrary(cscOptions: cscOptions, decompilerSettings: new DecompilerSettings(CSharp.LanguageVersion.CSharp3) {
 				AggressiveScalarReplacementOfAggregates = true
 			});
 		}

ICSharpCode.Decompiler/CSharp/OutputVisitor/CSharpOutputVisitor.cs

@@ -1524,15 +1524,26 @@ namespace ICSharpCode.Decompiler.CSharp.OutputVisitor
 			StartNode(namespaceDeclaration);
 			WriteKeyword(Roles.NamespaceKeyword);
 			namespaceDeclaration.NamespaceName.AcceptVisitor(this);
-			OpenBrace(policy.NamespaceBraceStyle);
+			if (namespaceDeclaration.IsFileScoped)
+			{
+				Semicolon();
+				NewLine();
+			}
+			else
+			{
+				OpenBrace(policy.NamespaceBraceStyle);
+			}
 			foreach (var member in namespaceDeclaration.Members)
 			{
 				member.AcceptVisitor(this);
 				MaybeNewLinesAfterUsings(member);
 			}
-			CloseBrace(policy.NamespaceBraceStyle);
-			OptionalSemicolon(namespaceDeclaration.LastChild);
-			NewLine();
+			if (!namespaceDeclaration.IsFileScoped)
+			{
+				CloseBrace(policy.NamespaceBraceStyle);
+				OptionalSemicolon(namespaceDeclaration.LastChild);
+				NewLine();
+			}
 			EndNode(namespaceDeclaration);
 		}
 

ICSharpCode.Decompiler/CSharp/Syntax/GeneralScope/NamespaceDeclaration.cs

@@ -42,6 +42,8 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 			}
 		}
 
+		public bool IsFileScoped { get; set; }
+
 		public CSharpTokenNode NamespaceToken {
 			get { return GetChildByRole(Roles.NamespaceKeyword); }
 		}

ICSharpCode.Decompiler/CSharp/Transforms/NormalizeBlockStatements.cs

@@ -11,6 +11,31 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 	class NormalizeBlockStatements : DepthFirstAstVisitor, IAstTransform
 	{
 		TransformContext context;
+		bool hasNamespace;
+		NamespaceDeclaration singleNamespaceDeclaration;
+
+		public override void VisitSyntaxTree(SyntaxTree syntaxTree)
+		{
+			singleNamespaceDeclaration = null;
+			hasNamespace = false;
+			base.VisitSyntaxTree(syntaxTree);
+			if (context.Settings.FileScopedNamespaces && singleNamespaceDeclaration != null)
+			{
+				singleNamespaceDeclaration.IsFileScoped = true;
+			}
+		}
+
+		public override void VisitNamespaceDeclaration(NamespaceDeclaration namespaceDeclaration)
+		{
+			singleNamespaceDeclaration = null;
+			if (!hasNamespace)
+			{
+				hasNamespace = true;
+				singleNamespaceDeclaration = namespaceDeclaration;
+			}
+			base.VisitNamespaceDeclaration(namespaceDeclaration);
+
+		}
 
 		public override void VisitIfElseStatement(IfElseStatement ifElseStatement)
 		{

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -142,10 +142,16 @@ namespace ICSharpCode.Decompiler
 				usePrimaryConstructorSyntax = false;
 				covariantReturns = false;
 			}
+			if (languageVersion < CSharp.LanguageVersion.CSharp10_0)
+			{
+				fileScopedNamespaces = false;
+			}
 		}
 
 		public CSharp.LanguageVersion GetMinimumRequiredVersion()
 		{
+			if (fileScopedNamespaces)
+				return CSharp.LanguageVersion.CSharp10_0;
 			if (nativeIntegers || initAccessors || functionPointers || forEachWithGetEnumeratorExtension
 				|| recordClasses || withExpressions || usePrimaryConstructorSyntax || covariantReturns)
 				return CSharp.LanguageVersion.CSharp9_0;
@@ -323,6 +329,24 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool fileScopedNamespaces = true;
+
+		/// <summary>
+		/// Use C# 10 file-scoped namespaces.
+		/// </summary>
+		[Category("C# 10.0 / VS 2022")]
+		[Description("DecompilerSettings.FileScopedNamespaces")]
+		public bool FileScopedNamespaces {
+			get { return fileScopedNamespaces; }
+			set {
+				if (fileScopedNamespaces != value)
+				{
+					fileScopedNamespaces = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool anonymousMethods = true;
 
 		/// <summary>

ILSpy/Options/DecompilerSettingsPanel.xaml.cs

@@ -26,6 +26,7 @@ using System.Windows.Data;
 using System.Xml.Linq;
 
 using ICSharpCode.ILSpy.Properties;
+using ICSharpCode.ILSpy.TreeNodes;
 
 namespace ICSharpCode.ILSpy.Options
 {
@@ -157,7 +158,7 @@ namespace ICSharpCode.ILSpy.Options
 			Settings = typeof(Decompiler.DecompilerSettings).GetProperties()
 				.Where(p => p.GetCustomAttribute<BrowsableAttribute>()?.Browsable != false)
 				.Select(p => new CSharpDecompilerSetting(p) { IsEnabled = (bool)p.GetValue(settings) })
-				.OrderBy(item => item.Category)
+				.OrderBy(item => item.Category, NaturalStringComparer.Instance)
 				.ThenBy(item => item.Description)
 				.ToArray();
 		}

ILSpy/Properties/Resources.Designer.cs

@@ -954,6 +954,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to Use file-scoped namespace declarations.
+        /// </summary>
+        public static string DecompilerSettings_FileScopedNamespaces {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.FileScopedNamespaces", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Transform to for, if possible.
         /// </summary>

ILSpy/Properties/Resources.resx

@@ -345,6 +345,9 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.FSpecificOptions" xml:space="preserve">
     <value>F#-specific options</value>
   </data>
+  <data name="DecompilerSettings.FileScopedNamespaces" xml:space="preserve">
+    <value>Use file-scoped namespace declarations</value>
+  </data>
   <data name="DecompilerSettings.ForStatement" xml:space="preserve">
     <value>Transform to for, if possible</value>
   </data>