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Detect async void lambdas in AsyncVoidAnalyzer (TUnit0031) #4758

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Merged
thomhurst merged 2 commits into from
Feb 13, 2026
+178 −9
Merged

Detect async void lambdas in AsyncVoidAnalyzer (TUnit0031) #4758

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Enhance AsyncVoidAnalyzer to detect async void lambdas and anonymous …
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141 changes: 141 additions & 0 deletions TUnit.Analyzers.Tests/AsyncVoidAnalyzerTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -47,4 +47,145 @@ public async Task Test()
"""
);
}

[Test]
public async Task Async_Void_Lambda_Raises_Error()
{
await Verifier
.VerifyAnalyzerAsync(
"""
using System;
using System.Threading.Tasks;
using TUnit.Core;

public class MyClass
{
[Test]
public void Test()
{
Action action = {|#0:async () =>
{
await Task.Delay(1);
}|};
}
}
""",

Verifier
.Diagnostic(Rules.AsyncVoidMethod)
.WithLocation(0)
);
}

[Test]
public async Task Async_Task_Lambda_Raises_No_Error()
{
await Verifier
.VerifyAnalyzerAsync(
"""
using System;
using System.Threading.Tasks;
using TUnit.Core;

public class MyClass
{
[Test]
public void Test()
{
Func<Task> action = async () =>
{
await Task.Delay(1);
};
}
}
"""
);
}

[Test]
public async Task Async_Void_AnonymousDelegate_Raises_Error()
{
await Verifier
.VerifyAnalyzerAsync(
"""
using System;
using System.Threading.Tasks;
using TUnit.Core;

public class MyClass
{
[Test]
public void Test()
{
Action action = {|#0:async delegate
{
await Task.Delay(1);
}|};
}
}
""",

Verifier
.Diagnostic(Rules.AsyncVoidMethod)
.WithLocation(0)
);
}

[Test]
public async Task Async_Void_Lambda_With_Parameter_Raises_Error()
{
await Verifier
.VerifyAnalyzerAsync(
"""
using System;
using System.Threading.Tasks;
using TUnit.Core;

public class MyClass
{
[Test]
public void Test()
{
Action<int> action = {|#0:async (x) =>
{
await Task.Delay(1);
}|};
}
}
""",

Verifier
.Diagnostic(Rules.AsyncVoidMethod)
.WithLocation(0)
);
}

[Test]
public async Task Async_Void_SimpleLambda_Raises_Error()
{
await Verifier
.VerifyAnalyzerAsync(
"""
using System;
using System.Threading.Tasks;
using TUnit.Core;

public class MyClass
{
[Test]
public void Test()
{
Action<int> action = {|#0:async x =>
{
await Task.Delay(1);
}|};
}
}
""",

Verifier
.Diagnostic(Rules.AsyncVoidMethod)
.WithLocation(0)
);
}
}
2 changes: 1 addition & 1 deletion TUnit.Analyzers/AnalyzerReleases.Shipped.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@

### New Rules

#### Test Method and Structure Rules

Check warning on line 5 in TUnit.Analyzers/AnalyzerReleases.Shipped.md

View workflow job for this annotation

GitHub Actions / modularpipeline (fr-FR) 

Le fichier de version d'analyseur 'AnalyzerReleases.Shipped.md' a un en-tête de version '#### Test Method and Structure Rules' non valide, ou celui-ci est manquant (https://github.com/dotnet/roslyn-analyzers/blob/main/src/Microsoft.CodeAnalysis.Analyzers/ReleaseTrackingAnalyzers.Help.md)
Rule ID | Category | Severity | Notes
--------|----------|----------|------------------------------------------------
TUnit0001 | Usage | Error | Test argument types don't match method parameters
Expand Down Expand Up @@ -62,7 +62,7 @@
Rule ID | Category | Severity | Notes
--------|----------|----------|------------------------------------------------
TUnit0015 | Usage | Error | Methods with [Timeout] must have a CancellationToken parameter
TUnit0031 | Usage | Error | Async void methods not allowed - return Task instead
TUnit0031 | Usage | Error | Async void methods and lambdas not allowed - return Task instead

#### AOT Compatibility Rules
Rule ID | Category | Severity | Notes
Expand Down
32 changes: 30 additions & 2 deletions TUnit.Analyzers/AsyncVoidAnalyzer.cs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
using System.Collections.Immutable;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;

namespace TUnit.Analyzers;
Expand All @@ -12,10 +14,14 @@ public class AsyncVoidAnalyzer : ConcurrentDiagnosticAnalyzer

protected override void InitializeInternal(AnalysisContext context)
{
context.RegisterSymbolAction(AnalyzeSyntax, SymbolKind.Method);
context.RegisterSymbolAction(AnalyzeMethod, SymbolKind.Method);
context.RegisterSyntaxNodeAction(AnalyzeLambda,
SyntaxKind.ParenthesizedLambdaExpression,
SyntaxKind.SimpleLambdaExpression,
SyntaxKind.AnonymousMethodExpression);
}

private void AnalyzeSyntax(SymbolAnalysisContext context)
private void AnalyzeMethod(SymbolAnalysisContext context)
{
if (context.Symbol is not IMethodSymbol methodSymbol)
{
Expand All @@ -29,4 +35,26 @@ private void AnalyzeSyntax(SymbolAnalysisContext context)
);
}
}

private void AnalyzeLambda(SyntaxNodeAnalysisContext context)
{
if (context.Node is not AnonymousFunctionExpressionSyntax anonymousFunction)
{
return;
}

if (!anonymousFunction.Modifiers.Any(SyntaxKind.AsyncKeyword))
{
return;
}

var symbol = context.SemanticModel.GetSymbolInfo(anonymousFunction).Symbol;

if (symbol is IMethodSymbol { ReturnsVoid: true })
{
context.ReportDiagnostic(Diagnostic.Create(Rules.AsyncVoidMethod,
anonymousFunction.GetLocation())
);
}
}
}
6 changes: 3 additions & 3 deletions TUnit.Analyzers/Resources.Designer.cs
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6 changes: 3 additions & 3 deletions TUnit.Analyzers/Resources.resx
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Original file line number Diff line number Diff line change
Expand Up @@ -217,13 +217,13 @@
<value>Class doesn't pick up tests from the base class</value>
</data>
<data name="TUnit0031Description" xml:space="preserve">
<value>Async void methods are not allowed.</value>
<value>Async void methods and lambdas are not allowed.</value>
</data>
<data name="TUnit0031MessageFormat" xml:space="preserve">
<value>Async void methods are not allowed</value>
<value>Async void methods and lambdas are not allowed</value>
</data>
<data name="TUnit0031Title" xml:space="preserve">
<value>Async void methods are not allowed</value>
<value>Async void methods and lambdas are not allowed</value>
</data>
<data name="TUnit0032Description" xml:space="preserve">
<value>Conflicting DependsOn and NotInParallel attributes.</value>
Expand Down
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