Performance regression in VS2026 in AvoidPassingTaskWithoutCancellationTokenAnalyzer

[WolfgangHG]

VS2026 builds of our project became drastically slower than VS2022 builds.

We use .NET 9 target framework, and we have this “global.json” in the solution root:

{
  "sdk": {
    "version": "9.0.0",
    "rollForward": "latestFeature"
  }
}

Some binlogs are privately attached to https://developercommunity.visualstudio.com/t/VS2026-Rebuild-is-much-slower-than-in-/11027380 where I first reported the problem. There you will also find some time measuring.

Building without analyzers (/p:RunAnalyzersDuringBuild=false) reduced the build time to values similar to VS2022 (still slightly slower).

During analysis of this issue, I found the reportanalyzer switch, and this one brought me to the root cause of the delay I think:

Here are some log snippets (the first line translates to “Total analyzer execution time”):

VS2022:

Gesamtausführungszeit des Analysetools: 10,801 Sekunden.
  Zeit (s)    %   Analysetool
  6,212   57   System.Windows.Forms.Analyzers.CSharp, Version=9.0.12.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
  6,194   57      System.Windows.Forms.CSharp.Analyzers.AvoidPassingTaskWithoutCancellationToken.AvoidPassingTaskWithoutCancellationTokenAnalyzer (WFO2001)
  0,018   <1      System.Windows.Forms.CSharp.Analyzers.MissingPropertySerializationConfiguration.MissingPropertySerializationConfigurationAnalyzer (WFO1000)
  2,546   23   Microsoft.CodeAnalysis.CSharp.NetAnalyzers, Version=9.0.12.32904, Culture=neutral, PublicKeyToken=31bf3856ad364e35

VS2026:

Gesamtausführungszeit des Analysetools: 64,305 Sekunden.
  Zeit (s)    %   Analysetool
  59,593   92   System.Windows.Forms.Analyzers.CSharp, Version=9.0.12.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
  59,572   92      System.Windows.Forms.CSharp.Analyzers.AvoidPassingTaskWithoutCancellationToken.AvoidPassingTaskWithoutCancellationTokenAnalyzer (WFO2001)
  0,021   <1      System.Windows.Forms.CSharp.Analyzers.MissingPropertySerializationConfiguration.MissingPropertySerializationConfigurationAnalyzer (WFO1000)
  2,385    3   Microsoft.CodeAnalysis.CSharp.NetAnalyzers, Version=9.0.12.32904, Culture=neutral, PublicKeyToken=31bf3856ad364e35

So it seems "System.Windows.Forms.CSharp.Analyzers.AvoidPassingTaskWithoutCancellationToken.AvoidPassingTaskWithoutCancellationTokenAnalyzer" causes the delay.

The file "C:\Program Files\Microsoft Visual Studio\18\Enterprise\MSBuild\Current\Bin\Roslyn\csc.exe" of VS2026 has file version 5.0.26.5402, the same file in VS2022 has 4.1400.25.41205

Adding a ".editorconfig" file with this line optimizes compile time:

dotnet_diagnostic.WFO2001.severity = none

[Youssef1313]

See also dotnet/roslyn#82055 (comment)