Add code fix for MSTEST0040 — AvoidUsingAssertsInAsyncVoidContext

src/Analyzers/MSTest.Analyzers.CodeFixes/AvoidUsingAssertsInAsyncVoidContextFixer.cs

@@ -0,0 +1,197 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Collections.Immutable;
+using System.Composition;
+
+using Analyzer.Utilities;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Editing;
+
+using MSTest.Analyzers.Helpers;
+
+namespace MSTest.Analyzers;
+
+/// <summary>
+/// Code fixer for <see cref="AvoidUsingAssertsInAsyncVoidContextAnalyzer"/>.
+/// </summary>
+[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(AvoidUsingAssertsInAsyncVoidContextFixer))]
+[Shared]
+public sealed class AvoidUsingAssertsInAsyncVoidContextFixer : CodeFixProvider
+{
+    /// <inheritdoc />
+    public sealed override ImmutableArray<string> FixableDiagnosticIds { get; }
+        = ImmutableArray.Create(DiagnosticIds.AvoidUsingAssertsInAsyncVoidContextRuleId);
+
+    /// <inheritdoc />
+    public override FixAllProvider GetFixAllProvider()
+        // See https://github.com/dotnet/roslyn/blob/main/docs/analyzers/FixAllProvider.md for more information on Fix All Providers
+        => WellKnownFixAllProviders.BatchFixer;
+
+    /// <inheritdoc />
+    public override async Task RegisterCodeFixesAsync(CodeFixContext context)
+    {
+        SyntaxNode root = await context.Document.GetRequiredSyntaxRootAsync(context.CancellationToken).ConfigureAwait(false);
+
+        Diagnostic diagnostic = context.Diagnostics[0];
+        SyntaxNode diagnosticNode = root.FindNode(diagnostic.Location.SourceSpan, getInnermostNodeForTie: true);
+
+        // Walk up the ancestors to find the nearest async void method or local function.
+        foreach (SyntaxNode ancestor in diagnosticNode.AncestorsAndSelf())
+        {
+            if (ancestor is MethodDeclarationSyntax methodDeclaration)
+            {
+                if (methodDeclaration.Modifiers.Any(SyntaxKind.AsyncKeyword) &&
+                    methodDeclaration.ReturnType.IsVoid() &&
+                    !methodDeclaration.Modifiers.Any(SyntaxKind.OverrideKeyword) &&
+                    !methodDeclaration.Modifiers.Any(SyntaxKind.VirtualKeyword) &&
+                    methodDeclaration.ExplicitInterfaceSpecifier is null)
+                {
+                    context.RegisterCodeFix(
+                        CodeAction.Create(
+                            title: CodeFixResources.AvoidUsingAssertsInAsyncVoidContextFix,
+                            createChangedDocument: ct => ChangeReturnTypeToTaskAsync(context.Document, methodDeclaration, ct),
+                            equivalenceKey: nameof(AvoidUsingAssertsInAsyncVoidContextFixer)),
+                        diagnostic);
+                }
+
+                break;
+            }
+
+            if (ancestor is LocalFunctionStatementSyntax localFunction)
+            {
+                if (localFunction.Modifiers.Any(SyntaxKind.AsyncKeyword) &&
+                    localFunction.ReturnType.IsVoid())
+                {
+                    context.RegisterCodeFix(
+                        CodeAction.Create(
+                            title: CodeFixResources.AvoidUsingAssertsInAsyncVoidContextFix,
+                            createChangedDocument: ct => ChangeReturnTypeToTaskAsync(context.Document, localFunction, ct),
+                            equivalenceKey: nameof(AvoidUsingAssertsInAsyncVoidContextFixer)),
+                        diagnostic);
+                }
+
+                break;
+            }
+
+            if (ancestor is AnonymousFunctionExpressionSyntax anonymousFunction)
+            {
+                // Only stop at async lambdas/delegates — they represent the async void context.
+                // For non-async lambdas, keep walking up to find the enclosing async void method/local function.
+                if (anonymousFunction.AsyncKeyword.IsKind(SyntaxKind.AsyncKeyword))
+                {
+                    // For async lambdas/anonymous functions, we don't provide a fix since changing to Task
+                    // would require changing the delegate type as well.
+                    break;
+                }
+            }
+        }
+    }
+
+    private static async Task<Document> ChangeReturnTypeToTaskAsync(
+        Document document,
+        MethodDeclarationSyntax methodDeclaration,
+        CancellationToken cancellationToken)
+    {
+        DocumentEditor editor = await DocumentEditor.CreateAsync(document, cancellationToken).ConfigureAwait(false);
+        MethodDeclarationSyntax newMethodDeclaration = methodDeclaration.WithReturnType(
+            SyntaxFactory.IdentifierName("Task").WithTriviaFrom(methodDeclaration.ReturnType));
+        editor.ReplaceNode(methodDeclaration, newMethodDeclaration);
+        Document updatedDocument = editor.GetChangedDocument();
+
+        return await EnsureSystemThreadingTasksImportAsync(updatedDocument, cancellationToken).ConfigureAwait(false);
+    }
+
+    private static async Task<Document> ChangeReturnTypeToTaskAsync(
+        Document document,
+        LocalFunctionStatementSyntax localFunction,
+        CancellationToken cancellationToken)
+    {
+        DocumentEditor editor = await DocumentEditor.CreateAsync(document, cancellationToken).ConfigureAwait(false);
+        LocalFunctionStatementSyntax newLocalFunction = localFunction.WithReturnType(
+            SyntaxFactory.IdentifierName("Task").WithTriviaFrom(localFunction.ReturnType));
+        editor.ReplaceNode(localFunction, newLocalFunction);
+        Document updatedDocument = editor.GetChangedDocument();
+
+        return await EnsureSystemThreadingTasksImportAsync(updatedDocument, cancellationToken).ConfigureAwait(false);
+    }
+
+    private static async Task<Document> EnsureSystemThreadingTasksImportAsync(Document document, CancellationToken cancellationToken)
+    {
+        SyntaxNode root = await document.GetRequiredSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
+        if (root is not CompilationUnitSyntax compilationUnit)
+        {
+            return document;
+        }
+
+        // Check file-level usings and namespace-scoped usings for an existing System.Threading.Tasks import.
+        if (HasSystemThreadingTasksUsing(compilationUnit.Usings))
+        {
+            return document;
+        }
+
+        foreach (NamespaceDeclarationSyntax ns in compilationUnit.DescendantNodes().OfType<NamespaceDeclarationSyntax>())
+        {
+            if (HasSystemThreadingTasksUsing(ns.Usings))
+            {
+                return document;
+            }
+        }
+
+        UsingDirectiveSyntax usingDirective = SyntaxFactory
+            .UsingDirective(SyntaxFactory.ParseName("System.Threading.Tasks").WithLeadingTrivia(SyntaxFactory.Space))
+            .WithTrailingTrivia(SyntaxFactory.ElasticCarriageReturnLineFeed);
+
+        // Insert in correct alphabetical position: after System.* usings that sort before "System.Threading.Tasks"
+        // and before any that sort after it or before any non-System usings.
+        int insertionIndex = compilationUnit.Usings.Count; // default: append after all usings
+        for (int i = 0; i < compilationUnit.Usings.Count; i++)
+        {
+            string? nameText = NormalizeUsingName(compilationUnit.Usings[i].Name?.ToString());
+            if (nameText is null)
+            {
+                continue;
+            }
+
+            bool isSystemNamespace = IsSystemNamespace(nameText);
+            if (!isSystemNamespace ||
+                string.Compare(nameText, "System.Threading.Tasks", StringComparison.Ordinal) > 0)
+            {
+                insertionIndex = i;
+                break;
+            }
+        }
+
+        SyntaxList<UsingDirectiveSyntax> newUsings = compilationUnit.Usings.Insert(insertionIndex, usingDirective);
+        return document.WithSyntaxRoot(compilationUnit.WithUsings(newUsings));
+    }
+
+    private static bool HasSystemThreadingTasksUsing(SyntaxList<UsingDirectiveSyntax> usings)
+        => usings.Any(
+            u => u.Alias is null &&
+                 !u.StaticKeyword.IsKind(SyntaxKind.StaticKeyword) &&
+                 string.Equals(NormalizeUsingName(u.Name?.ToString()), "System.Threading.Tasks", StringComparison.Ordinal));
+
+    private static bool IsSystemNamespace(string nameText)
+        => string.Equals(nameText, "System", StringComparison.Ordinal) ||
+           nameText.StartsWith("System.", StringComparison.Ordinal);
+
+    private static string? NormalizeUsingName(string? name)
+    {
+        if (name is null)
+        {
+            return null;
+        }
+
+        // Strip the "global::" qualifier if present so that "global::System.Threading.Tasks" is recognized.
+        const string globalPrefix = "global::";
+        return name.StartsWith(globalPrefix, StringComparison.Ordinal)
+            ? name[globalPrefix.Length..]
+            : name;
+    }
+}

src/Analyzers/MSTest.Analyzers.CodeFixes/CodeFixResources.resx

@@ -213,6 +213,9 @@
   <data name="AvoidOutRefTestMethodParametersFix" xml:space="preserve">
     <value>Remove 'out' and 'ref' modifiers</value>
   </data>
+  <data name="AvoidUsingAssertsInAsyncVoidContextFix" xml:space="preserve">
+    <value>Change return type to 'Task'</value>
+  </data>
   <data name="RemoveDuplicateDataRowFix" xml:space="preserve">
     <value>Remove duplicate 'DataRow'</value>
   </data>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.cs.xlf

@@ -37,6 +37,11 @@
         <target state="translated">Odebrat modifikátory out a ref</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Změnit přístupnost metody na private</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.de.xlf

@@ -37,6 +37,11 @@
         <target state="translated">Entfernen der Modifizierer „out“ und „ref“</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Methodenzugriff auf „privat“ ändern</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.es.xlf

@@ -37,6 +37,11 @@
         <target state="translated">Quitar modificadores 'out' y 'ref'</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Cambiar la accesibilidad del método a "private"</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.fr.xlf

@@ -37,6 +37,11 @@
         <target state="translated">Supprimer les modificateurs « out » et « ref »</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Remplacer l’accessibilité de la méthode par « privé »</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.it.xlf

@@ -37,6 +37,11 @@
         <target state="translated">Rimuovi i modificatori 'out' e 'ref'</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Modifica l'accessibilità del metodo in 'privato'</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.ja.xlf

@@ -37,6 +37,11 @@
         <target state="translated">'out' 修飾子と 'ref' 修飾子を削除する</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">メソッドのアクセシビリティを 'private' に変更する</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.ko.xlf

@@ -37,6 +37,11 @@
         <target state="translated">'out' 및 'ref' 한정자 제거</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">메서드 접근성 '비공개'로 변경하기</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.pl.xlf

@@ -37,6 +37,11 @@
         <target state="translated">Usuń modyfikatory „out” i „ref”</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Zmień dostępność metody na „private” (prywatna)</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.pt-BR.xlf

@@ -37,6 +37,11 @@
         <target state="translated">Remova os modificadores ''out'' e ''ref''</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Alterar a acessibilidade do método para 'privado'</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.ru.xlf

@@ -37,6 +37,11 @@
         <target state="translated">Удалите модификаторы "out" и "ref"</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Изменить доступность метода на "private"</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.tr.xlf

@@ -37,6 +37,11 @@
         <target state="translated">'out' ve 'ref' değiştiricilerini kaldırın</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">Yöntem erişilebilirliğini ‘özel’ olarak değiştir</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.zh-Hans.xlf

@@ -37,6 +37,11 @@
         <target state="translated">移除 "out" 或 "ref" 修饰符</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">将方法可访问性更改为“private”</target>

src/Analyzers/MSTest.Analyzers.CodeFixes/xlf/CodeFixResources.zh-Hant.xlf

@@ -37,6 +37,11 @@
         <target state="translated">移除 'out' 和 'ref' 修飾元</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextFix">
+        <source>Change return type to 'Task'</source>
+        <target state="new">Change return type to 'Task'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ChangeMethodAccessibilityToPrivateFix">
         <source>Change method accessibility to 'private'</source>
         <target state="translated">將方法協助工具變更為 'private'</target>