feat: add class level mutation control (for method only)

src/Stryker.Core/Stryker.Core.UnitTest/Instrumentation/RedirectMethodEngineShould.cs

@@ -0,0 +1,76 @@
+using System.Linq;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Shouldly;
+using Stryker.Core.Instrumentation;
+
+namespace Stryker.Core.UnitTest.Instrumentation;
+
+[TestClass]
+public class RedirectMethodEngineShould
+{
+    [TestMethod]
+    public void InjectSimpleMutatedMethod()
+    {
+        const string OriginalClass = """
+                                     class Test
+                                     {
+                                         public void Basic(int x)
+                                         {
+                                             x++;
+                                         }
+                                     }
+                                     """;
+        const string MutatedMethod = @"public void Basic(int x) {x--;}";
+        var parsedClass = SyntaxFactory.ParseSyntaxTree(OriginalClass).GetRoot().DescendantNodes().OfType<ClassDeclarationSyntax>().Single();
+        var parsedMethod = (MethodDeclarationSyntax) SyntaxFactory.ParseMemberDeclaration(MutatedMethod);
+        var originalMethod =  parsedClass.Members.OfType<MethodDeclarationSyntax>().Single();
+
+        var engine = new RedirectMethodEngine();
+
+        var injected = engine.InjectRedirect(parsedClass, SyntaxFactory.ParseExpression("ActiveMutation(2)"), originalMethod, parsedMethod);
+
+        injected.Members.Count.ShouldBe(3);
+
+        injected.ToString().ShouldBeEquivalentTo("""
+                                                 class Test
+                                                 {
+                                                 public void Basic(int x)
+                                                 {if(ActiveMutation(2)){Basic_1(x);}else{Basic_0(x);}}
+                                                     public void Basic_0(int x)
+                                                     {
+                                                         x++;
+                                                     }
+                                                 public void Basic_1(int x) {x--;}
+                                                 }
+                                                 """);
+    }
+
+    [TestMethod]
+    public void RollbackMutatedMethod()
+    {
+        const string OriginalClass = """
+                                     class Test
+                                     {
+                                         public void Basic(int x)
+                                         {
+                                             x++;
+                                         }
+                                     }
+                                     """;
+        const string MutatedMethod = @"public void Basic(int x) {x--;}";
+        var parsedClass = SyntaxFactory.ParseSyntaxTree(OriginalClass).GetRoot().DescendantNodes().OfType<ClassDeclarationSyntax>().Single();
+        var parsedMethod = (MethodDeclarationSyntax) SyntaxFactory.ParseMemberDeclaration(MutatedMethod);
+        var originalMethod =  parsedClass.Members.OfType<MethodDeclarationSyntax>().Single();
+
+        var engine = new RedirectMethodEngine();
+        var injected = engine.InjectRedirect(parsedClass, SyntaxFactory.ParseExpression("ActiveMutation(2)"), originalMethod, parsedMethod);
+
+        // find the entry point
+        var mutatedEntry =  injected.Members.OfType<MethodDeclarationSyntax>().First( p=> p.Identifier.ToString() == originalMethod.Identifier.ToString());
+        var rolledBackClass = engine.RemoveInstrumentationFrom(injected ,mutatedEntry);
+
+        rolledBackClass.ToString().ShouldBeSemantically(OriginalClass);
+    }
+}

src/Stryker.Core/Stryker.Core/Compiling/CSharpRollbackProcess.cs

@@ -222,7 +222,7 @@ private SyntaxTree RemoveCompileErrorMutations(SyntaxTree originalTree, IEnumera
             // find the mutated node in the new tree
             var nodeToRemove = trackedTree.GetCurrentNode(brokenMutation);
             // remove the mutated node using its MutantPlacer remove method and update the tree
-            trackedTree = trackedTree.ReplaceNode(nodeToRemove, MutantPlacer.RemoveMutant(nodeToRemove));
+            trackedTree = MutantPlacer.RemoveMutation(nodeToRemove);
         }
 
         return trackedTree.SyntaxTree;

src/Stryker.Core/Stryker.Core/Helpers/RoslynHelper.cs

@@ -197,4 +197,37 @@ public static bool ContainsNodeThatVerifies(this SyntaxNode node, Func<SyntaxNod
             return (child.Parent is not AnonymousFunctionExpressionSyntax function || function.ExpressionBody != child)
                    && (child.Parent is not LocalFunctionStatementSyntax localFunction || localFunction.ExpressionBody != child);
         } ).Any(predicate);
+
+
+    /// <summary>
+    /// Ensure a statement is in a syntax bock.
+    /// </summary>
+    /// <param name="statement">the statement to put into a block.</param>
+    /// <returns>a block containing <paramref name="statement"/>, or <paramref name="statement"/> if it is already a block</returns>
+    public static BlockSyntax AsBlock(this StatementSyntax statement) => statement as BlockSyntax ?? SyntaxFactory.Block(statement);
+
+    /// <summary>
+    /// Ensure an expression is in a syntax bock.
+    /// </summary>
+    /// <param name="expression">the expression to put into a block.</param>
+    /// <returns>a block containing <paramref name="expression"/></returns>
+    public static BlockSyntax AsBlock(this ExpressionSyntax expression) =>SyntaxFactory.ExpressionStatement(expression).AsBlock();
+
+    /// <summary>
+    /// Ensure a <see cref="SyntaxNode"/> is followed by a trailing newline
+    /// </summary>
+    /// <typeparam name="T">Type of node, must be a SyntaxNode</typeparam>
+    /// <param name="node">Node</param>
+    /// <returns><paramref name="node"/> with a trailing newline</returns>
+    public static T WithTrailingNewLine<T>(this T node) where T: SyntaxNode
+        => node.WithTrailingTrivia(SyntaxFactory.CarriageReturnLineFeed);
+
+
+    public static ClassDeclarationSyntax RemoveNamedMember(this ClassDeclarationSyntax classNode, string memberName) =>
+        classNode.RemoveNode(classNode.Members.First( m => m switch
+        {
+            MethodDeclarationSyntax method => method.Identifier.ToString() == memberName,
+            PropertyDeclarationSyntax field => field.Identifier.ToString() == memberName,
+            _ => false
+        }), SyntaxRemoveOptions.KeepNoTrivia);
 }

src/Stryker.Core/Stryker.Core/Instrumentation/BaseEngine.cs

@@ -46,4 +46,10 @@ public SyntaxNode RemoveInstrumentation(SyntaxNode node)
         }
         throw new InvalidOperationException($"Expected a {typeof(T).Name}, found:\n{node.ToFullString()}.");
     }
+
+    public virtual SyntaxNode RemoveInstrumentationFrom(SyntaxNode tree, SyntaxNode instrumentation)
+    {
+        var restoredNode = RemoveInstrumentation(instrumentation);
+        return tree.ReplaceNode(instrumentation, restoredNode);
+    }
 }

src/Stryker.Core/Stryker.Core/Instrumentation/IInstrumentCode.cs

@@ -21,4 +21,6 @@ public interface IInstrumentCode
     /// <returns>returns a node without the instrumentation.</returns>
     /// <exception cref="InvalidOperationException">if the node was not instrumented (by this instrumentingEngine)</exception>
     SyntaxNode RemoveInstrumentation(SyntaxNode node);
+
+    SyntaxNode RemoveInstrumentationFrom(SyntaxNode tree, SyntaxNode instrumentation);
 }

src/Stryker.Core/Stryker.Core/Instrumentation/IfInstrumentationEngine.cs

@@ -2,6 +2,7 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Stryker.Core.Helpers;
 
 namespace Stryker.Core.Instrumentation;
 
@@ -20,10 +21,8 @@ internal class IfInstrumentationEngine : BaseEngine<IfStatementSyntax>
     /// <remarks>This method works with statement and block.</remarks>
     public IfStatementSyntax InjectIf(ExpressionSyntax condition, StatementSyntax originalNode, StatementSyntax mutatedNode) =>
         SyntaxFactory.IfStatement(condition,
-            AsBlock(mutatedNode),
-            SyntaxFactory.ElseClause(AsBlock(originalNode))).WithAdditionalAnnotations(Marker);
-
-    private static BlockSyntax AsBlock(StatementSyntax code) => code as BlockSyntax ?? SyntaxFactory.Block(code);
+            mutatedNode.AsBlock(),
+            SyntaxFactory.ElseClause(originalNode.AsBlock())).WithAdditionalAnnotations(Marker);
 
     /// <summary>
     /// Returns the original code.

src/Stryker.Core/Stryker.Core/Instrumentation/RedirectMethodEngine.cs

@@ -0,0 +1,91 @@
+using System;
+using System.Linq;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Stryker.Core.Helpers;
+
+namespace Stryker.Core.Instrumentation;
+
+internal class RedirectMethodEngine : BaseEngine<MethodDeclarationSyntax>
+{
+    private const string _redirectHints = "RedirectHints";
+
+    public ClassDeclarationSyntax InjectRedirect(ClassDeclarationSyntax originalClass,
+        ExpressionSyntax condition,
+        MethodDeclarationSyntax originalMethod,
+        MethodDeclarationSyntax mutatedMethod)
+    {
+        if (!originalClass.Contains(originalMethod))
+        {
+            throw new ArgumentException($"Syntax tree does not contains {originalMethod.Identifier}.", nameof(originalMethod));
+        }
+
+        // we need to rename the original method
+        var index = 0;
+        var newNameForOriginal = FindNewName(originalClass, originalMethod, ref index);
+        var newNameForMutated = FindNewName(originalClass, originalMethod, ref index);
+
+        // generates a redirecting method
+        // call to original method
+        var originalCall = GenerateRedirectedInvocation(originalMethod, newNameForOriginal);
+        var mutatedCall = GenerateRedirectedInvocation(originalMethod, newNameForMutated);
+
+        var redirectHints = new SyntaxAnnotation(_redirectHints, $"{originalMethod.Identifier.ToString()},{newNameForOriginal},{newNameForMutated}");
+
+        var redirector = originalMethod
+            .WithBody(SyntaxFactory.Block(
+                SyntaxFactory.IfStatement(condition, mutatedCall.AsBlock(),
+                SyntaxFactory.ElseClause(originalCall.AsBlock())
+                ))).WithExpressionBody(null).WithoutLeadingTrivia();
+
+        // update the class
+        var resultingClass = originalClass.RemoveNode(originalMethod, SyntaxRemoveOptions.KeepNoTrivia)
+            ?.AddMembers([redirector.WithTrailingNewLine().WithAdditionalAnnotations(redirectHints),
+                originalMethod.WithIdentifier(SyntaxFactory.Identifier(newNameForOriginal)).WithTrailingNewLine().WithAdditionalAnnotations(redirectHints),
+                mutatedMethod.WithIdentifier(SyntaxFactory.Identifier(newNameForMutated)).WithTrailingNewLine().WithAdditionalAnnotations(redirectHints)]);
+        return resultingClass;
+    }
+
+    private static InvocationExpressionSyntax GenerateRedirectedInvocation(MethodDeclarationSyntax originalMethod, string redirectedName)
+        => SyntaxFactory.InvocationExpression(SyntaxFactory.IdentifierName(redirectedName),
+            SyntaxFactory.ArgumentList( SyntaxFactory.SeparatedList(
+                originalMethod.ParameterList.Parameters.Select(p => SyntaxFactory.Argument( SyntaxFactory.IdentifierName(p.Identifier))))));
+
+    private static string FindNewName(ClassDeclarationSyntax originalClass, MethodDeclarationSyntax originalMethod, ref int index)
+    {
+        string newNameForOriginal;
+        do
+        {
+            newNameForOriginal = $"{originalMethod.Identifier}_{index++}";
+        }
+        while (originalClass.Members.Any(m => m is MethodDeclarationSyntax method && method.Identifier.ToFullString() == newNameForOriginal));
+        return newNameForOriginal;
+    }
+
+    protected override SyntaxNode Revert(MethodDeclarationSyntax node) => throw new NotSupportedException("Cannot revert node in place.");
+
+    public override SyntaxNode RemoveInstrumentationFrom(SyntaxNode tree, SyntaxNode instrumentation)
+    {
+        var annotation = instrumentation.GetAnnotations(_redirectHints).FirstOrDefault()?.Data;
+        if (string.IsNullOrEmpty(annotation))
+        {
+            throw new InvalidOperationException($"Unable to find details to rollback this instrumentation: '{instrumentation}'");
+        }
+
+        var method = (MethodDeclarationSyntax) instrumentation;
+        var names = annotation.Split(',').ToList();
+
+
+        var parentClass = (ClassDeclarationSyntax) method.Parent;
+        var renamedMethod = (MethodDeclarationSyntax) parentClass.Members.
+            First( m=> m is MethodDeclarationSyntax meth && meth.Identifier.Text == names[1]);
+        parentClass = parentClass.TrackNodes(renamedMethod);
+        // we need to remove redirection method and replacement method and restore the name of the original method
+        parentClass = parentClass.RemoveNamedMember(names[2]).RemoveNamedMember(names[0]);
+        var oldNode = parentClass.GetCurrentNode(renamedMethod);
+        parentClass = parentClass.ReplaceNode(oldNode, renamedMethod.WithIdentifier(SyntaxFactory.Identifier(names[0])));
+        return parentClass;
+    }
+
+}

src/Stryker.Core/Stryker.Core/Mutants/CsharpNodeOrchestrators/BaseFunctionOrchestrator.cs

@@ -99,6 +99,12 @@ public SyntaxNode RemoveInstrumentation(SyntaxNode node)
         return SwitchToThisBodies(typedNode, null, expression).WithoutAnnotations(Marker);
     }
 
+    public SyntaxNode RemoveInstrumentationFrom(SyntaxNode tree, SyntaxNode instrumentation)
+    {
+        var restoredNode = RemoveInstrumentation(instrumentation);
+        return tree.ReplaceNode(instrumentation, restoredNode);
+    }
+
     /// <inheritdoc/>
     protected override T InjectMutations(T sourceNode, T targetNode, SemanticModel semanticModel, MutationContext context)
     {

src/Stryker.Core/Stryker.Core/Mutants/MutantPlacer.cs

@@ -152,6 +152,20 @@ public static SyntaxNode RemoveMutant(SyntaxNode nodeToRemove)
         throw new InvalidOperationException($"Unable to find an engine to remove injection from this node: '{nodeToRemove}'");
     }
 
+    public static SyntaxNode RemoveMutation(SyntaxNode nodeToRemove)
+    {
+        var annotatedNode = nodeToRemove.GetAnnotatedNodes(Injector).FirstOrDefault();
+        if (annotatedNode != null)
+        {
+            var id = annotatedNode.GetAnnotations(Injector).First().Data;
+            if (!string.IsNullOrEmpty(id))
+            {
+                return instrumentEngines[id].engine.RemoveInstrumentationFrom(nodeToRemove.SyntaxTree.GetRoot(), annotatedNode);
+            }
+        }
+        throw new InvalidOperationException($"Unable to find an engine to remove injection from this node: '{nodeToRemove}'");
+    }
+
     /// <summary>
     /// Returns true if the node contains a mutation requiring all child mutations to be removed when it has to be removed
     /// </summary>

src/Stryker.Core/Stryker.Core/Mutants/MutationStore.cs

@@ -10,7 +10,6 @@
 
 namespace Stryker.Core.Mutants;
 
-
 /// <summary>
 /// This enum is used to track the syntax 'level' of mutations that are injected in the code.
 /// </summary>
@@ -143,6 +142,7 @@ public bool StoreMutationsAtDesiredLevel(IEnumerable<Mutant> store, MutationCont
             controller.StoreMutations(store);
             return true;
         }
+
         Logger.LogDebug("There is no structure to control {MutationsCount} mutations. They are dropped.", store.Count());
         foreach (var mutant in store)
         {