Added support for ConditionalAttribute

ICSharpCode.Decompiler/CSharp/CSharpDecompiler.cs

@@ -44,6 +44,7 @@ namespace ICSharpCode.Decompiler.CSharp
 	{
 		readonly DecompilerTypeSystem typeSystem;
 		readonly DecompilerSettings settings;
+		private SyntaxTree syntaxTree;
 
 		List<IILTransform> ilTransforms = GetILTransforms();
 
@@ -229,7 +230,7 @@ namespace ICSharpCode.Decompiler.CSharp
 		public SyntaxTree DecompileModuleAndAssemblyAttributes()
 		{
 			var decompilationContext = new SimpleTypeResolveContext(typeSystem.MainAssembly);
-			SyntaxTree syntaxTree = new SyntaxTree();
+			syntaxTree = new SyntaxTree();
 			DoDecompileModuleAndAssemblyAttributes(decompilationContext, syntaxTree);
 			RunTransforms(syntaxTree, decompilationContext);
 			return syntaxTree;
@@ -275,7 +276,7 @@ namespace ICSharpCode.Decompiler.CSharp
 		public SyntaxTree DecompileWholeModuleAsSingleFile()
 		{
 			var decompilationContext = new SimpleTypeResolveContext(typeSystem.MainAssembly);
-			SyntaxTree syntaxTree = new SyntaxTree();
+			syntaxTree = new SyntaxTree();
 			DoDecompileModuleAndAssemblyAttributes(decompilationContext, syntaxTree);
 			DoDecompileTypes(typeSystem.ModuleDefinition.Types, decompilationContext, syntaxTree);
 			RunTransforms(syntaxTree, decompilationContext);
@@ -293,7 +294,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (types == null)
 				throw new ArgumentNullException(nameof(types));
 			var decompilationContext = new SimpleTypeResolveContext(typeSystem.MainAssembly);
-			SyntaxTree syntaxTree = new SyntaxTree();
+			syntaxTree = new SyntaxTree();
 			DoDecompileTypes(types, decompilationContext, syntaxTree);
 			RunTransforms(syntaxTree, decompilationContext);
 			return syntaxTree;
@@ -307,7 +308,7 @@ namespace ICSharpCode.Decompiler.CSharp
 			if (definitions == null)
 				throw new ArgumentNullException(nameof(definitions));
 			ITypeDefinition parentTypeDef = null;
-			var syntaxTree = new SyntaxTree();
+			syntaxTree = new SyntaxTree();
 			foreach (var def in definitions) {
 				if (def == null)
 					throw new ArgumentException("definitions contains null element");
@@ -594,11 +595,23 @@ namespace ICSharpCode.Decompiler.CSharp
 				transform.Run(function, context);
 				function.CheckInvariant(ILPhase.Normal);
 			}
-			
+
+			AddDefinesForConditionalAttributes(function);
 			var statementBuilder = new StatementBuilder(specializingTypeSystem, decompilationContext, method);
 			entityDecl.AddChild(statementBuilder.ConvertAsBlock(function.Body), Roles.Body);
 		}
 
+		void AddDefinesForConditionalAttributes(ILFunction function)
+		{
+			foreach (var call in function.Descendants.OfType<CallInstruction>()) {
+				var attr = call.Method.GetAttribute(new TopLevelTypeName("System.Diagnostics", nameof(ConditionalAttribute)));
+				var symbolName = attr?.PositionalArguments.FirstOrDefault()?.ConstantValue as string;
+				if (symbolName == null)
+					continue;
+				syntaxTree.InsertChildAfter(null, new PreProcessorDirective(PreProcessorDirectiveType.Define, symbolName), Roles.PreProcessorDirective);
+			}
+		}
+
 		EntityDeclaration DoDecompile(FieldDefinition fieldDefinition, IField field, ITypeResolveContext decompilationContext)
 		{
 			Debug.Assert(decompilationContext.CurrentMember == field);

ICSharpCode.Decompiler/CSharp/Transforms/IntroduceUsingDeclarations.cs

@@ -43,6 +43,8 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 			requiredImports.ImportedNamespaces.Add("System"); // always import System, even when not necessary
 			
 			var usingScope = new UsingScope();
+
+			var insertionPoint = compilationUnit.Children.LastOrDefault(n => n is PreProcessorDirective p && p.Type == PreProcessorDirectiveType.Define);
 			
 			// Now add using declarations for those namespaces:
 			foreach (string ns in requiredImports.ImportedNamespaces.OrderByDescending(n => n)) {
@@ -58,7 +60,7 @@ namespace ICSharpCode.Decompiler.CSharp.Transforms
 					if (reference != null)
 						usingScope.Usings.Add(reference);
 				}
-				compilationUnit.InsertChildAfter(null, new UsingDeclaration { Import = nsType }, SyntaxTree.MemberRole);
+				compilationUnit.InsertChildAfter(insertionPoint, new UsingDeclaration { Import = nsType }, SyntaxTree.MemberRole);
 			}
 			
 			if (!FullyQualifyAmbiguousTypeNames)

ICSharpCode.Decompiler/Tests/CorrectnessTestRunner.cs

@@ -145,6 +145,12 @@ namespace ICSharpCode.Decompiler.Tests
 			RunCS(options: options);
 		}
 
+		[Test]
+		public void ConditionalAttr([ValueSource("defaultOptions")] CompilerOptions options)
+		{
+			RunCS(options: options);
+		}
+
 		void RunCS([CallerMemberName] string testName = null, CompilerOptions options = CompilerOptions.UseDebug)
 		{
 			string testFileName = testName + ".cs";

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

@@ -128,6 +128,7 @@
     <Compile Include="PrettyTestRunner.cs" />
     <Compile Include="RoundtripAssembly.cs" />
     <Compile Include="TestCases\Correctness\CompoundAssignment.cs" />
+    <Compile Include="TestCases\Correctness\ConditionalAttr.cs" />
     <Compile Include="TestCases\Correctness\ControlFlow.cs" />
     <Compile Include="TestCases\Correctness\Conversions.cs" />
     <Compile Include="TestCases\Correctness\DecimalFields.cs" />

ICSharpCode.Decompiler/Tests/TestCases/Correctness/ConditionalAttr.cs

@@ -0,0 +1,26 @@
+#define PRINT
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.Correctness
+{
+
+	class ConditionalAttr
+	{
+		[Conditional("PRINT")]
+		static void Print()
+		{
+			Console.WriteLine("Text!");
+		}
+
+		static void Main()
+		{
+			Print();
+		}
+	}
+}