fix: Refactor C# mutation orchestration to a simpler design

src/Stryker.Core/Stryker.Core.UnitTest/AssertExtensions.cs

@@ -17,10 +17,7 @@ public static class AssertionExtensions
         /// </summary>
         /// <param name="actual">Resulted code</param>
         /// <param name="expected">Expected code</param>
-        public static void ShouldBeSemantically(this string actual, string expected)
-        {
-            ShouldBeSemantically(CSharpSyntaxTree.ParseText(actual).GetRoot(), CSharpSyntaxTree.ParseText(expected).GetRoot());
-        }
+        public static void ShouldBeSemantically(this string actual, string expected) => ShouldBeSemantically(CSharpSyntaxTree.ParseText(actual), CSharpSyntaxTree.ParseText(expected));
 
         /// <summary>
         /// Compares two syntax trees and asserts equality
@@ -29,14 +26,9 @@ public static void ShouldBeSemantically(this string actual, string expected)
         /// <param name="expected">Expected code</param>
         /// <remarks>Warning: this code tries to pinpoint the first different lines, but it will work on string comparison, so it may pinpoint spaces
         /// or new line variations, hiding the real differences.</remarks>
-        public static void ShouldBeSemantically(this SyntaxNode actual, SyntaxNode expected)
+        public static void ShouldBeSemantically(this SyntaxTree actual, SyntaxTree expected)
         {
-            // for some reason, nodes can be different while being textually the same
-            if (actual.ToFullString() == expected.ToFullString())
-            {
-                return;
-            }
-            var isSame = SyntaxFactory.AreEquivalent(actual, expected);
+            var isSame = actual.IsEquivalentTo(expected);
 
             if (!isSame)
             {
@@ -63,12 +55,12 @@ public static void ShouldBeWithNewlineReplace(this string actual, string expecte
             actual.ShouldBe(replaced);
         }
 
-        public static void ShouldNotContainErrors(this SyntaxNode actual)
+        public static void ShouldNotContainErrors(this SyntaxTree actual)
         {
-            var errors = actual.SyntaxTree.GetDiagnostics().Count(x => x.Severity == DiagnosticSeverity.Error);
+            var errors = actual.GetDiagnostics().Count(x => x.Severity == DiagnosticSeverity.Error);
             if (errors > 0)
             {
-                errors.ShouldBe(0, $"Actual code has build errors!\n{actual.ToFullString()}\nerrors: {string.Join(Environment.NewLine, actual.SyntaxTree.GetDiagnostics())}");
+                errors.ShouldBe(0, $"Actual code has build errors!\n{actual.GetText()}\nerrors: {string.Join(Environment.NewLine, actual.GetDiagnostics())}");
             }
         }
 

src/Stryker.Core/Stryker.Core.UnitTest/Compiling/CSharpRollbackProcessTests.cs

@@ -119,8 +119,8 @@ public void SomeLinq()
                 helpers.Add(CSharpSyntaxTree.ParseText(code, path: name, encoding: Encoding.UTF32));
             }
 
-            var mutant = mutator.Mutate(syntaxTree.GetRoot(), null);
-            helpers.Add(mutant.SyntaxTree);
+            var mutant = mutator.Mutate(syntaxTree, null);
+            helpers.Add(mutant);
 
             var references = new List<string> {
                 typeof(object).Assembly.Location,
@@ -203,8 +203,9 @@ private void RefreshAccountNumber()
                 helpers.Add(CSharpSyntaxTree.ParseText(code, path: name, encoding: Encoding.UTF32));
             }
 
-            var mutant = mutator.Mutate(syntaxTree.GetRoot(), null);
-            helpers.Add(mutant.SyntaxTree);
+            var mutant = mutator.Mutate(syntaxTree, null);
+
+            helpers.Add(mutant);
 
             var references = new List<string> {
                 typeof(object).Assembly.Location,

src/Stryker.Core/Stryker.Core.UnitTest/Mutants/CsharpMutantOrchestratorTests.cs

@@ -1,4 +1,3 @@
-using System.Collections.Generic;
 using System.Linq;
 using Microsoft.CodeAnalysis.CSharp;
 using Shouldly;
@@ -105,7 +104,7 @@ public void ShouldMutateBlockStatements()
             expected = @"private int Move()
     {if(StrykerNamespace.MutantControl.IsActive(1)){}else		    {
     			    ;
-    		    } return default(int);}";
+    		    }}";
 
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -114,10 +113,10 @@ public void ShouldMutateBlockStatements()
         public void ShouldAddReturnDefaultToOperator()
         {
             string source = @"public static string operator+ (TestClass value, TestClass other)
-{;
+{ while(true) return value;
 }";
             string expected = @"public static string operator+ (TestClass value, TestClass other)
-{if(StrykerNamespace.MutantControl.IsActive(0)){}else{;
+{if(StrykerNamespace.MutantControl.IsActive(0)){}else{ while((StrykerNamespace.MutantControl.IsActive(2)?!(true):(StrykerNamespace.MutantControl.IsActive(1)?false:true))) return value;
 }return default(string);}";
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -154,10 +153,11 @@ public void ShouldProperlyMutatePrefixUnitaryExpressionStatement()
         public void ShouldMutateExpressionBodiedLocalFunction()
         {
             string source = @"void TestMethod(){
-void SomeMethod()  => (true && SomeOtherMethod(out var x)) ? x : 5;
+int SomeMethod()  => (true && SomeOtherMethod(out var x)) ? x : 5;
 }";
             string expected = @"void TestMethod(){if(StrykerNamespace.MutantControl.IsActive(0)){}else{
-void SomeMethod()  {if(StrykerNamespace.MutantControl.IsActive(1)){return!((true && SomeOtherMethod(out var x)) )? x : 5;}else{if(StrykerNamespace.MutantControl.IsActive(2)){return(true || SomeOtherMethod(out var x)) ? x : 5;}else{((StrykerNamespace.MutantControl.IsActive(3)?false:true )&& SomeOtherMethod(out var x)) ? x : 5;}}};}}";
+int SomeMethod()  {if(StrykerNamespace.MutantControl.IsActive(1)){return!((true && SomeOtherMethod(out var x)) )? x : 5;}else{if(StrykerNamespace.MutantControl.IsActive(2)){return(true || SomeOtherMethod(out var x)) ? x : 5;}else{return ((StrykerNamespace.MutantControl.IsActive(3)?false:true )&& SomeOtherMethod(out var x)) ? x : 5;}}};}}
+}";
 
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -500,9 +500,9 @@ string SomeLocalFunction()
         public void ShouldMutateConditionalExpressionOnArrayDeclaration()
         {
             var source =
-                @"public static IEnumerable<int> Foo() => new int[] { }.ToArray().Any(x => x==1)?.OrderBy(e => e).ToList();";
+                @"public static IEnumerable<int> Foo() => new int[] { }.ToArray()!.Any(x => x==1)?.OrderBy(e => e).ToList();";
             var expected =
-                @"public static IEnumerable<int> Foo() => (StrykerNamespace.MutantControl.IsActive(2)?new int[] { }.ToArray().Any(x => x==1)?.OrderByDescending(e => e).ToList():(StrykerNamespace.MutantControl.IsActive(0)?new int[] { }.ToArray().All(x => x==1):new int[] { }.ToArray().Any(x => (StrykerNamespace.MutantControl.IsActive(1)?x!=1:x==1)))?.OrderBy(e => e).ToList());";
+                @"public static IEnumerable<int> Foo() => (StrykerNamespace.MutantControl.IsActive(2)?new int[] { }.ToArray()!.Any(x => x==1)?.OrderByDescending(e => e).ToList():(StrykerNamespace.MutantControl.IsActive(0)?new int[] { }.ToArray()!.All(x => x==1):new int[] { }.ToArray()!.Any(x => (StrykerNamespace.MutantControl.IsActive(1)?x!=1:x==1)))?.OrderBy(e => e).ToList());";
 
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -515,7 +515,7 @@ public void ShouldMutateSuppressNullableWarningExpressionOnArrayDeclaration()
 var employeePerson = group.First().Entitlement!.Employee.Person;}";
             var expected =
                 @"public static void Foo(){if(StrykerNamespace.MutantControl.IsActive(0)){}else{
-var employeePerson = (StrykerNamespace.MutantControl.IsActive(1)?group.FirstOrDefault().Entitlement!.Employee.Person:group.First().Entitlement!.Employee.Person);}}";
+var employeePerson = (StrykerNamespace.MutantControl.IsActive(1)?group.FirstOrDefault():group.First()).Entitlement!.Employee.Person;}}";
 
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -557,7 +557,7 @@ public void ShouldMutateArrayInitializer()
 int[] test = {};
 }else{
 int[] test = { 1 };
-}}return default(int[]);}";
+}}}";
 
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -729,7 +729,7 @@ public void ShouldMutateComplexExpressionBodiedMethod()
         [Fact]
         public void ShouldMutateExpressionBodiedStaticConstructor()
         {
-            string source = @"static Test()  => (true && SomeOtherMethod(out var x)) ? x : 5;";
+            string source = @"static Test() => (true && SomeOtherMethod(out var x)) ? x : 5;";
             string expected =
                 @"static Test() {using(new StrykerNamespace.MutantContext()){if(StrykerNamespace.MutantControl.IsActive(0)){!((true && SomeOtherMethod(out var x)) )? x : 5;}else{if(StrykerNamespace.MutantControl.IsActive(1)){(true || SomeOtherMethod(out var x)) ? x : 5;}else{((StrykerNamespace.MutantControl.IsActive(2)?false:true )&& SomeOtherMethod(out var x)) ? x : 5;}}}}}";
 
@@ -1222,7 +1222,7 @@ public void MutationsShouldHaveLinespan()
 {
 	var test3 = 2 + 5;
 }";
-            _target.Mutate(CSharpSyntaxTree.ParseText(source).GetRoot(), null);
+            _target.Mutate(CSharpSyntaxTree.ParseText(source), null);
 
             var mutants = _target.GetLatestMutantBatch().ToList();
             mutants.Count.ShouldBe(2);
@@ -1249,7 +1249,7 @@ public static bool InvokeIfNotNull(this Action a)
 		}
 	}
 }";
-            _target.Mutate(CSharpSyntaxTree.ParseText(source).GetRoot(), null);
+            _target.Mutate(CSharpSyntaxTree.ParseText(source), null);
 
             var mutants = _target.GetLatestMutantBatch().ToList();
             mutants.Count.ShouldBe(7);
@@ -1268,11 +1268,11 @@ public void ShouldAddReturnDefaultToMethods()
         {
             string source = @"bool TestMethod()
 {
-	;
+	while(true) return false;
 }";
             string expected = @"bool TestMethod()
 {if(StrykerNamespace.MutantControl.IsActive(0)){}else{
-	;
+	while((StrykerNamespace.MutantControl.IsActive(2)?!(true):(StrykerNamespace.MutantControl.IsActive(1)?false:true))) return (StrykerNamespace.MutantControl.IsActive(3)?true:false);
 }return default(bool);}";
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -1281,10 +1281,10 @@ public void ShouldAddReturnDefaultToMethods()
         public void ShouldAddReturnDefaultToConversion()
         {
             string source = @"public static explicit operator string(TestClass value)
-{;
+{ while(true) return value;
 }";
             string expected = @"public static explicit operator string(TestClass value)
-{if(StrykerNamespace.MutantControl.IsActive(0)){}else{;
+{if(StrykerNamespace.MutantControl.IsActive(0)){}else{ while((StrykerNamespace.MutantControl.IsActive(2)?!(true):(StrykerNamespace.MutantControl.IsActive(1)?false:true))) return value;
 }return default(string);}";
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -1303,12 +1303,10 @@ public void ShouldNotMutateConstDeclaration()
         public void ShouldAddReturnDefaultToAsyncMethods()
         {
             string source = @"public async Task<bool> TestMethod()
-{
-	;
+{   while(true) return false;
 }";
             string expected = @"public async Task<bool> TestMethod()
-{if(StrykerNamespace.MutantControl.IsActive(0)){}else{
-	;
+{if(StrykerNamespace.MutantControl.IsActive(0)){}else{  while((StrykerNamespace.MutantControl.IsActive(2)?!(true):(StrykerNamespace.MutantControl.IsActive(1)?false:true))) return (StrykerNamespace.MutantControl.IsActive(3)?true:false);
 }return default(bool);}";
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -1366,12 +1364,10 @@ public static IEnumerable<object> Extracting<T>(this IEnumerable<T> enumerable)
         public void ShouldAddReturnDefaultToAsyncWithFullNamespaceMethods()
         {
             string source = @"public async System.Threading.Tasks.Task<bool> TestMethod()
-{
-	;
+{  while(true) return false;
 }";
             string expected = @"public async System.Threading.Tasks.Task<bool> TestMethod()
-{if(StrykerNamespace.MutantControl.IsActive(0)){}else{
-	;
+{if(StrykerNamespace.MutantControl.IsActive(0)){}else{  while((StrykerNamespace.MutantControl.IsActive(2)?!(true):(StrykerNamespace.MutantControl.IsActive(1)?false:true))) return (StrykerNamespace.MutantControl.IsActive(3)?true:false);
 }return default(bool);}";
             ShouldMutateSourceInClassToExpected(source, expected);
         }
@@ -1404,6 +1400,21 @@ public void ShouldNotAddReturnDefaultToMethodsWithReturnTypeVoid()
             ShouldMutateSourceInClassToExpected(source, expected);
         }
 
+        [Theory]
+        [InlineData("{return 0;}")]
+        [InlineData("{return 1; throw Exception();}")]
+        [InlineData("{return 1;yield return 0;}")]
+        [InlineData("{return 1;yield break;}")]
+        [InlineData("{;}")]
+        public void ShouldNotAddReturnOnSomeBlocks(string code)
+        {
+            string source = @$"
+int TestMethod()
+// Stryker disable all
+{code}";
+            ShouldMutateSourceInClassToExpected(source, source);
+        }
+
         [Fact]
         public void ShouldSkipStringsInSwitchExpression()
         {
@@ -1478,7 +1489,7 @@ public void ShouldMutatePropertiesInArrowFormEvenWithComplexConstruction()
 static TestClass(){}}";
 
             var expected = @"class Test {
-string Value {get {if(StrykerNamespace.MutantControl.IsActive(0)){return!(Out(out var x))? ""empty"": """";}else{return Out(out var x)? (StrykerNamespace.MutantControl.IsActive(1)?"""":""empty""): (StrykerNamespace.MutantControl.IsActive(2)?""Stryker was here!"":"""");}return default(string);}}
+string Value {get {if(StrykerNamespace.MutantControl.IsActive(0)){return!(Out(out var x))? ""empty"": """";}else{return Out(out var x)? (StrykerNamespace.MutantControl.IsActive(1)?"""":""empty""): (StrykerNamespace.MutantControl.IsActive(2)?""Stryker was here!"":"""");}}}
 static TestClass(){using(new StrykerNamespace.MutantContext()){}}}";
 
             ShouldMutateSourceInClassToExpected(source, expected);
@@ -1496,8 +1507,7 @@ static string Value
 static TestClass(){}";
 
             var expected = @"static string Value
-{
-	get {if(StrykerNamespace.MutantControl.IsActive(0)){}else{ return (StrykerNamespace.MutantControl.IsActive(1)?"""":""TestDescription"");
+{get {if(StrykerNamespace.MutantControl.IsActive(0)){}else{ return (StrykerNamespace.MutantControl.IsActive(1)?"""":""TestDescription"");
         }
 return default(string);
         }
@@ -1508,7 +1518,7 @@ static string Value
             ShouldMutateSourceInClassToExpected(source, expected);
         }
 
-        [Fact]
+       [Fact]
         public void ShouldMarkStaticMutationStaticInPropertiesInitializer()
         {
             var source = @"class Test {
@@ -1521,6 +1531,18 @@ public void ShouldMarkStaticMutationStaticInPropertiesInitializer()
             _target.Mutants.First().IsStaticValue.ShouldBeTrue();
         }
 
+        [Fact]
+        public void ShouldMutateStaticPropertiesInArrowFormEvenWithComplexConstruction()
+        {
+            var source = @"class Test {
+static string Value => Out(out var x)? ""empty"": """";}";
+
+            var expected = @"class Test {
+static string Value {get {if(StrykerNamespace.MutantControl.IsActive(0)){return!(Out(out var x))? ""empty"": """";}else{return Out(out var x)? (StrykerNamespace.MutantControl.IsActive(1)?"""":""empty""): (StrykerNamespace.MutantControl.IsActive(2)?""Stryker was here!"":"""");}}}}";
+
+            ShouldMutateSourceInClassToExpected(source, expected);
+        }
+
         [Fact]
         public void ShouldMutatePropertiesAsArrowExpression()
         {

src/Stryker.Core/Stryker.Core.UnitTest/Mutants/MutantOrchestratorTestsBase.cs

@@ -26,11 +26,11 @@ public MutantOrchestratorTestsBase()
 
         protected void ShouldMutateSourceToExpected(string actual, string expected)
         {
-            var actualNode = _target.Mutate(CSharpSyntaxTree.ParseText(actual).GetRoot(), null);
-            actual = actualNode.ToFullString();
+            var actualNode = _target.Mutate(CSharpSyntaxTree.ParseText(actual), null);
+            actual = actualNode.GetRoot().ToFullString();
             actual = actual.Replace(_injector.HelperNamespace, "StrykerNamespace");
-            actualNode = CSharpSyntaxTree.ParseText(actual).GetRoot();
-            var expectedNode = CSharpSyntaxTree.ParseText(expected).GetRoot();
+            actualNode = CSharpSyntaxTree.ParseText(actual);
+            var expectedNode = CSharpSyntaxTree.ParseText(expected);
             actualNode.ShouldBeSemantically(expectedNode);
             actualNode.ShouldNotContainErrors();
         }