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Emit VSTHRD003 warning when awaiting on foreign tasks from properties #1244

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merged 1 commit into from
Oct 24, 2023
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Emit VSTHRD003 warning when awaiting on foreign tasks from properties #1244

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45 changes: 29 additions & 16 deletions src/Microsoft.VisualStudio.Threading.Analyzers.CSharp/VSTHRD003UseJtfRunAsyncAnalyzer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,30 @@ public override void Initialize(AnalysisContext context)
context.RegisterSyntaxNodeAction(Utils.DebuggableWrapper(this.AnalyzeLambdaExpression), SyntaxKind.ParenthesizedLambdaExpression);
}

private static bool IsSymbolAlwaysOkToAwait(ISymbol? symbol)
{
if (symbol is IFieldSymbol field)
{
// Allow the TplExtensions.CompletedTask and related fields.
if (field.ContainingType.Name == Types.TplExtensions.TypeName && field.BelongsToNamespace(Types.TplExtensions.Namespace) &&
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both this and the conditional on 88 are a little bit difficult to grok based on initial read. Consider making a method with a descriptive name to make it easier to understand at a glance.

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I agree it is. I have a code comment above that explains it, and this is the method that keeps things simple for the caller. :)

(field.Name == Types.TplExtensions.CompletedTask || field.Name == Types.TplExtensions.CanceledTask || field.Name == Types.TplExtensions.TrueTask || field.Name == Types.TplExtensions.FalseTask))
{
return true;
}
}
else if (symbol is IPropertySymbol property)
{
// Explicitly allow Task.CompletedTask
if (property.ContainingType.Name == Types.Task.TypeName && property.BelongsToNamespace(Types.Task.Namespace) &&
property.Name == Types.Task.CompletedTask)
{
return true;
}
}

return false;
}

private void AnalyzeArrowExpressionClause(SyntaxNodeAnalysisContext context)
{
var arrowExpressionClause = (ArrowExpressionClauseSyntax)context.Node;
Expand Down Expand Up @@ -156,6 +180,9 @@ private void AnalyzeAwaitExpression(SyntaxNodeAnalysisContext context)
symbolType = localSymbol.Type;
dataflowAnalysisCompatibleVariable = true;
break;
case IPropertySymbol propertySymbol when !IsSymbolAlwaysOkToAwait(propertySymbol):
symbolType = propertySymbol.Type;
break;
case IParameterSymbol parameterSymbol:
symbolType = parameterSymbol.Type;
dataflowAnalysisCompatibleVariable = true;
Expand Down Expand Up @@ -209,23 +236,9 @@ private void AnalyzeAwaitExpression(SyntaxNodeAnalysisContext context)
}

ISymbol? definition = declarationSemanticModel.GetSymbolInfo(memberAccessSyntax, cancellationToken).Symbol;
if (definition is IFieldSymbol field)
{
// Allow the TplExtensions.CompletedTask and related fields.
if (field.ContainingType.Name == Types.TplExtensions.TypeName && field.BelongsToNamespace(Types.TplExtensions.Namespace) &&
(field.Name == Types.TplExtensions.CompletedTask || field.Name == Types.TplExtensions.CanceledTask || field.Name == Types.TplExtensions.TrueTask || field.Name == Types.TplExtensions.FalseTask))
{
return null;
}
}
else if (definition is IPropertySymbol property)
if (IsSymbolAlwaysOkToAwait(definition))
{
// Explicitly allow Task.CompletedTask
if (property.ContainingType.Name == Types.Task.TypeName && property.BelongsToNamespace(Types.Task.Namespace) &&
property.Name == Types.Task.CompletedTask)
{
return null;
}
return null;
}
}
}
Expand Down
56 changes: 56 additions & 0 deletions .../Microsoft.VisualStudio.Threading.Analyzers.Tests/VSTHRD003UseJtfRunAsyncAnalyzerTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1243,6 +1243,62 @@ async Task FooAsync() {
await CSVerify.VerifyAnalyzerAsync(test);
}

[Fact]
public async Task ReportWarningWhenAwaitingTaskReturningProperty()
{
var test = @"
using System.Threading.Tasks;

class Tests
{
async Task GetTask(TaskCompletionSource<int> tcs)
{
await [|tcs.Task|];
}
}
";
await CSVerify.VerifyAnalyzerAsync(test);
}

[Fact]
public async Task DoNotReportWarningWhenAwaitingTaskPropertyThatWasSetInContext()
{
var test = @"
using System.Threading.Tasks;

class Tests
{
private Task MyTaskProperty { get; set; }

async Task GetTask()
{
this.MyTaskProperty = Task.Run(() => {});
await this.MyTaskProperty;
}
}
";
await CSVerify.VerifyAnalyzerAsync(test);
}

[Fact]
public async Task ReportWarningWhenAwaitingTaskPropertyThatWasNotSetInContext()
{
var test = @"
using System.Threading.Tasks;

class Tests
{
private Task MyTaskProperty { get; set; } = Task.Run(() => {});

async Task GetTask()
{
await [|this.MyTaskProperty|];
}
}
";
await CSVerify.VerifyAnalyzerAsync(test);
}

private DiagnosticResult CreateDiagnostic(int line, int column, int length) =>
CSVerify.Diagnostic().WithSpan(line, column, line, column + length);
}