Implement analyzer to warn for use of Assert methods in async void

src/Analyzers/MSTest.Analyzers/AnalyzerReleases.Unshipped.md

@@ -6,3 +6,4 @@ Rule ID | Category | Severity | Notes
 --------|----------|----------|-------
 MSTEST0038 | Usage | Warning | AvoidAssertAreSameWithValueTypesAnalyzer, [Documentation](https://learn.microsoft.com/dotnet/core/testing/mstest-analyzers/mstest0038)
 MSTEST0039 | Usage | Info | UseNewerAssertThrowsAnalyzer, [Documentation](https://learn.microsoft.com/dotnet/core/testing/mstest-analyzers/mstest0039)
+MSTEST0040 | Usage | Warning | AvoidUsingAssertsInAsyncVoidContextAnalyzer, [Documentation](https://learn.microsoft.com/dotnet/core/testing/mstest-analyzers/mstest0040)

src/Analyzers/MSTest.Analyzers/AvoidUsingAssertsInAsyncVoidContextAnalyzer.cs

@@ -0,0 +1,89 @@
+// 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 Analyzer.Utilities.Extensions;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Operations;
+
+using MSTest.Analyzers.Helpers;
+
+namespace MSTest.Analyzers;
+
+/// <summary>
+/// MSTEST0040: <inheritdoc cref="Resources.AvoidUsingAssertsInAsyncVoidContextTitle"/>.
+/// </summary>
+[DiagnosticAnalyzer(LanguageNames.CSharp, LanguageNames.VisualBasic)]
+public sealed class AvoidUsingAssertsInAsyncVoidContextAnalyzer : DiagnosticAnalyzer
+{
+    private static readonly LocalizableResourceString Title = new(nameof(Resources.AvoidUsingAssertsInAsyncVoidContextTitle), Resources.ResourceManager, typeof(Resources));
+    private static readonly LocalizableResourceString MessageFormat = new(nameof(Resources.AvoidUsingAssertsInAsyncVoidContextMessageFormat), Resources.ResourceManager, typeof(Resources));
+    private static readonly LocalizableResourceString Description = new(nameof(Resources.AvoidUsingAssertsInAsyncVoidContextDescription), Resources.ResourceManager, typeof(Resources));
+
+    internal static readonly DiagnosticDescriptor Rule = DiagnosticDescriptorHelper.Create(
+        DiagnosticIds.AvoidUsingAssertsInAsyncVoidContextRuleId,
+        Title,
+        MessageFormat,
+        Description,
+        Category.Usage,
+        DiagnosticSeverity.Warning,
+        isEnabledByDefault: true);
+
+    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; }
+        = ImmutableArray.Create(Rule);
+
+    public override void Initialize(AnalysisContext context)
+    {
+        context.EnableConcurrentExecution();
+        context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+
+        context.RegisterCompilationStartAction(context =>
+        {
+            Compilation compilation = context.Compilation;
+            INamedTypeSymbol? assertSymbol = compilation.GetOrCreateTypeByMetadataName(WellKnownTypeNames.MicrosoftVisualStudioTestToolsUnitTestingAssert);
+            if (assertSymbol is not null)
+            {
+                context.RegisterOperationAction(context => AnalyzeOperation(context, assertSymbol), OperationKind.Invocation);
+            }
+        });
+    }
+
+    private static void AnalyzeOperation(OperationAnalysisContext context, INamedTypeSymbol assertSymbol)
+    {
+        var operation = (IInvocationOperation)context.Operation;
+        if (!IsAsyncVoidContext(operation, context.ContainingSymbol) ||
+            !assertSymbol.Equals(operation.TargetMethod.ContainingType, SymbolEqualityComparer.Default))
+        {
+            return;
+        }
+
+        context.ReportDiagnostic(operation.CreateDiagnostic(Rule));
+    }
+
+    private static bool IsAsyncVoidContext(IInvocationOperation invocationOperation, ISymbol containingSymbol)
+    {
+        if (containingSymbol is IMethodSymbol { IsAsync: true, ReturnsVoid: true })
+        {
+            return true;
+        }
+
+        // For the case of anonymous functions or local functions, the ContainingSymbol is the method that contains the anonymous function.
+        // So, we need to special case this.
+        IOperation? operation = invocationOperation;
+        while (operation is not null)
+        {
+            if (operation is IAnonymousFunctionOperation { Symbol.IsAsync: true, Symbol.ReturnsVoid: true } or
+                ILocalFunctionOperation { Symbol.IsAsync: true, Symbol.ReturnsVoid: true })
+            {
+                return true;
+            }
+
+            operation = operation.Parent;
+        }
+
+        return false;
+    }
+}

src/Analyzers/MSTest.Analyzers/Helpers/DiagnosticIds.cs

@@ -44,4 +44,5 @@ internal static class DiagnosticIds
     public const string UseProperAssertMethodsRuleId = "MSTEST0037";
     public const string AvoidAssertAreSameWithValueTypesRuleId = "MSTEST0038";
     public const string UseNewerAssertThrowsRuleId = "MSTEST0039";
+    public const string AvoidUsingAssertsInAsyncVoidContextRuleId = "MSTEST0040";
 }

src/Analyzers/MSTest.Analyzers/PublicAPI.Unshipped.txt

@@ -1,5 +1,9 @@
 #nullable enable
 MSTest.Analyzers.AvoidAssertAreSameWithValueTypesAnalyzer
 MSTest.Analyzers.AvoidAssertAreSameWithValueTypesAnalyzer.AvoidAssertAreSameWithValueTypesAnalyzer() -> void
+MSTest.Analyzers.AvoidUsingAssertsInAsyncVoidContextAnalyzer
+MSTest.Analyzers.AvoidUsingAssertsInAsyncVoidContextAnalyzer.AvoidUsingAssertsInAsyncVoidContextAnalyzer() -> void
 override MSTest.Analyzers.AvoidAssertAreSameWithValueTypesAnalyzer.Initialize(Microsoft.CodeAnalysis.Diagnostics.AnalysisContext! context) -> void
 override MSTest.Analyzers.AvoidAssertAreSameWithValueTypesAnalyzer.SupportedDiagnostics.get -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.DiagnosticDescriptor!>
+override MSTest.Analyzers.AvoidUsingAssertsInAsyncVoidContextAnalyzer.Initialize(Microsoft.CodeAnalysis.Diagnostics.AnalysisContext! context) -> void
+override MSTest.Analyzers.AvoidUsingAssertsInAsyncVoidContextAnalyzer.SupportedDiagnostics.get -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.DiagnosticDescriptor!>

src/Analyzers/MSTest.Analyzers/Resources.resx

@@ -558,4 +558,13 @@ The type declaring these methods should also respect the following rules:
   <data name="AvoidAssertAreSameWithValueTypesDescription" xml:space="preserve">
     <value>Use 'Assert.AreEqual'/'Assert.AreNotEqual' instead of 'Assert.AreSame'/'Assert.AreNotSame' when comparing value types. Passing a value type to 'Assert.AreSame'/'Assert.AreNotSame' will be boxed (creating a new object). Because 'Assert.AreSame'/'Assert.AreNotSame' does the comparison by reference, 'Assert.AreSame' will fail when boxing happens, and 'Assert.AreNotSame' will always pass.</value>
   </data>
+  <data name="AvoidUsingAssertsInAsyncVoidContextTitle" xml:space="preserve">
+    <value>Do not assert inside 'async void' contexts</value>
+  </data>
+  <data name="AvoidUsingAssertsInAsyncVoidContextMessageFormat" xml:space="preserve">
+    <value>Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</value>
+  </data>
+  <data name="AvoidUsingAssertsInAsyncVoidContextDescription" xml:space="preserve">
+    <value>Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</value>
+  </data>
 </root>

src/Analyzers/MSTest.Analyzers/xlf/Resources.cs.xlf

@@ -147,6 +147,21 @@ Typ deklarující tyto metody by měl také respektovat následující pravidla:
         <target state="translated">Vyhněte se [ExpectedException]</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextDescription">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextMessageFormat">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextTitle">
+        <source>Do not assert inside 'async void' contexts</source>
+        <target state="new">Do not assert inside 'async void' contexts</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ClassCleanupShouldBeValidDescription">
         <source>Methods marked with '[ClassCleanup]' should follow the following layout to be valid:
 -it can't be declared on a generic class without the 'InheritanceBehavior' mode is set

src/Analyzers/MSTest.Analyzers/xlf/Resources.de.xlf

@@ -147,6 +147,21 @@ Der Typ, der diese Methoden deklariert, sollte auch die folgenden Regeln beachte
         <target state="translated">„[ExpectedException]“ vermeiden</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextDescription">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextMessageFormat">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextTitle">
+        <source>Do not assert inside 'async void' contexts</source>
+        <target state="new">Do not assert inside 'async void' contexts</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ClassCleanupShouldBeValidDescription">
         <source>Methods marked with '[ClassCleanup]' should follow the following layout to be valid:
 -it can't be declared on a generic class without the 'InheritanceBehavior' mode is set

src/Analyzers/MSTest.Analyzers/xlf/Resources.es.xlf

@@ -147,6 +147,21 @@ El tipo que declara estos métodos también debe respetar las reglas siguientes:
         <target state="translated">Evitar '[ExpectedException]'</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextDescription">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextMessageFormat">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextTitle">
+        <source>Do not assert inside 'async void' contexts</source>
+        <target state="new">Do not assert inside 'async void' contexts</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ClassCleanupShouldBeValidDescription">
         <source>Methods marked with '[ClassCleanup]' should follow the following layout to be valid:
 -it can't be declared on a generic class without the 'InheritanceBehavior' mode is set

src/Analyzers/MSTest.Analyzers/xlf/Resources.fr.xlf

@@ -147,6 +147,21 @@ Le type doit être une classe
         <target state="translated">Éviter « [ExpectedException] »</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextDescription">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextMessageFormat">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextTitle">
+        <source>Do not assert inside 'async void' contexts</source>
+        <target state="new">Do not assert inside 'async void' contexts</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ClassCleanupShouldBeValidDescription">
         <source>Methods marked with '[ClassCleanup]' should follow the following layout to be valid:
 -it can't be declared on a generic class without the 'InheritanceBehavior' mode is set

src/Analyzers/MSTest.Analyzers/xlf/Resources.it.xlf

@@ -147,6 +147,21 @@ Anche il tipo che dichiara questi metodi deve rispettare le regole seguenti:
         <target state="translated">Evita '[ExpectedException]'</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextDescription">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextMessageFormat">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextTitle">
+        <source>Do not assert inside 'async void' contexts</source>
+        <target state="new">Do not assert inside 'async void' contexts</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ClassCleanupShouldBeValidDescription">
         <source>Methods marked with '[ClassCleanup]' should follow the following layout to be valid:
 -it can't be declared on a generic class without the 'InheritanceBehavior' mode is set

src/Analyzers/MSTest.Analyzers/xlf/Resources.ja.xlf

@@ -147,6 +147,21 @@ The type declaring these methods should also respect the following rules:
         <target state="translated">'[ExpectedException]' を回避する</target>
         <note />
       </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextDescription">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas. Exceptions that are thrown in this context will be unobserved exceptions. When using VSTest, they will be silently swallowed. When using Microsoft.Testing.Platform, they may crash the process.</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextMessageFormat">
+        <source>Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</source>
+        <target state="new">Do not assert inside 'async void' methods, local functions, or lambdas because they may not fail the test</target>
+        <note />
+      </trans-unit>
+      <trans-unit id="AvoidUsingAssertsInAsyncVoidContextTitle">
+        <source>Do not assert inside 'async void' contexts</source>
+        <target state="new">Do not assert inside 'async void' contexts</target>
+        <note />
+      </trans-unit>
       <trans-unit id="ClassCleanupShouldBeValidDescription">
         <source>Methods marked with '[ClassCleanup]' should follow the following layout to be valid:
 -it can't be declared on a generic class without the 'InheritanceBehavior' mode is set