RoutePatternAnalyzer causes stack overflow on C# file with a lot of string operations

[timmydo]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

A file with a lot of string + operations (generated code) causes a stack overflow in the route pattern analyzer.

aspnetcore/src/Framework/AspNetCoreAnalyzers/src/Analyzers/RouteEmbeddedLanguage/RoutePatternAnalyzer.cs

Line 52 in a5833f7

Analyze(context, child.AsNode()!, wellKnownTypes, routeUsageCache, cancellationToken);

Expected Behavior

clean compile

Steps To Reproduce

git clone https://github.com/timmydo/dotnet8p3analyzer1.git
cd dotnet8p3analyzer1
dotnet build

Exceptions (if any)

$ dotnet build
MSBuild version 17.6.0-preview-23174-01+e7de13307 for .NET
  Determining projects to restore...
  Restored D:\tmp\t2\dotnet8p3analyzer1\dotnet8p3.csproj (in 83 ms).
C:\Program Files\dotnet\sdk\8.0.100-preview.3.23178.7\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.RuntimeIdentifierInference.targets(287,5): message NETSDK1057: You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy [D:\tmp\t2\dotnet8p3analy
zer1\dotnet8p3.csproj]
C:\Program Files\dotnet\sdk\8.0.100-preview.3.23178.7\Roslyn\Microsoft.CSharp.Core.targets(80,5): error : Stack overflow. [D:\tmp\t2\dotnet8p3analyzer1\dotnet8p3.csproj]
C:\Program Files\dotnet\sdk\8.0.100-preview.3.23178.7\Roslyn\Microsoft.CSharp.Core.targets(80,5): error : Repeat 1425 times: [D:\tmp\t2\dotnet8p3analyzer1\dotnet8p3.csproj]
C:\Program Files\dotnet\sdk\8.0.100-preview.3.23178.7\Roslyn\Microsoft.CSharp.Core.targets(80,5): error : -------------------------------- [D:\tmp\t2\dotnet8p3analyzer1\dotnet8p3.csproj]
C:\Program Files\dotnet\sdk\8.0.100-preview.3.23178.7\Roslyn\Microsoft.CSharp.Core.targets(80,5): error :    at Microsoft.AspNetCore.Analyzers.RouteEmbeddedLanguage.RoutePatternAnalyzer.Analyze(Microsoft.CodeAnalysis.Diagnostics.SemanticModelAnalysisContext, Microsoft.C
odeAnalysis.SyntaxNode, Microsoft.AspNetCore.App.Analyzers.Infrastructure.WellKnownTypes, Microsoft.AspNetCore.App.Analyzers.Infrastructure.RouteUsageCache, System.Threading.CancellationToken) [D:\tmp\t2\dotnet8p3analyzer1\dotnet8p3.csproj]
C:\Program Files\dotnet\sdk\8.0.100-preview.3.23178.7\Roslyn\Microsoft.CSharp.Core.targets(80,5): error : -------------------------------- [D:\tmp\t2\dotnet8p3analyzer1\dotnet8p3.csproj]
C:\Program Files\dotnet\sdk\8.0.100-preview.3.23178.7\Roslyn\Microsoft.CSharp.Core.targets(80,5): error :    at Microsoft.AspNetCore.Analyzers.RouteEmbeddedLanguage.RoutePatternAnalyzer.AnalyzeSemanticModel(Microsoft.CodeAnalysis.Diagnostics.SemanticModelAnalysisContext
) [D:\tmp\t2\dotnet8p3analyzer1\dotnet8p3.csproj]

.NET Version

8.0.100-preview.3.23178.7

Anything else?

No response

[timmydo]

@JamesNK @captainsafia

[jaredpar]

The rough pattern of the analyzer today is roughly

  private void Analyze(
        SemanticModelAnalysisContext context,
        SyntaxNode node)
    {
        foreach (var child in node.ChildNodesAndTokens())
        {
            if (child.IsNode)
            {
                Analyze(context, child.AsNode()!);
            }
            else
            {
                var token = child.AsToken();
                // do work

That is going to lend itself to these types of problems when dealing with extremely long binary expressions. Or other deeply nested calls like deeply chained fluent API calls. Instead I would consider using the following pattern:

foreach (var token in node.DescendantTokens())
{
    // do work
}

[JamesNK]

@jaredpar Thanks. Yeah, this definitely needs to change.

I have a PR - #48105. There are some comments about using DescendantTokens(). Will probably do something slightly different because we want to use FilteredSpan optimization in the future.

[JamesNK]

I created dotnet/roslyn#68136. The JSON analyzer uses recursion and I copied the implementation.