Add analyzer to suggest using cooperative cancellation for timeout

[Copilot]

This PR introduces a new analyzer MSTEST0045 that warns users when they use [Timeout] attribute without explicitly setting CooperativeCancellation = true. This prepares users for a future breaking change where cooperative cancellation will become the default behavior.

Problem

Currently, the TimeoutAttribute has a CooperativeCancellation property that defaults to false. In a future version (v5.0), cooperative cancellation will become the default behavior. To help users prepare for this breaking change, we need an analyzer that encourages them to explicitly opt into the recommended behavior.

Solution

The new analyzer UseCooperativeCancellationForTimeoutAnalyzer detects:

• [Timeout] attributes on test methods without CooperativeCancellation specified
• [Timeout] attributes with CooperativeCancellation = false explicitly set

And reports an Info-level diagnostic suggesting to use CooperativeCancellation = true.

Examples

❌ Will trigger diagnostic:

[TestMethod]
[Timeout(5000)] // Missing CooperativeCancellation
public void MyTest() { }

[TestMethod]  
[Timeout(5000, CooperativeCancellation = false)] // Explicitly false
public void MyTest() { }

✅ No diagnostic:

[TestMethod]
[Timeout(5000, CooperativeCancellation = true)] // Explicitly true - recommended
public void MyTest() { }

Implementation Details

• Analyzer ID: MSTEST0045
• Category: Usage
• Severity: Info
• Scope: Only analyzes [Timeout] attributes on test methods ([TestMethod], [DataTestMethod], etc.)

Files Added/Modified

• ✅ UseCooperativeCancellationForTimeoutAnalyzer.cs - Main analyzer implementation
• ✅ UseCooperativeCancellationForTimeoutAnalyzerTests.cs - Comprehensive unit tests
• ✅ Updated WellKnownTypeNames.cs to include TimeoutAttribute
• ✅ Updated DiagnosticIds.cs with MSTEST0045
• ✅ Updated resource files with localized diagnostic messages
• ✅ Updated public API and analyzer release documentation

Test Coverage

The implementation includes comprehensive tests covering:

• Timeout without cooperative cancellation → diagnostic
• Timeout with CooperativeCancellation = true → no diagnostic
• Timeout with CooperativeCancellation = false → diagnostic
• Timeout on non-test methods → no diagnostic
• Various test method types (TestMethod, DataTestMethod)
• TestTimeout enum usage scenarios

Fixes #5761.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• cflvsblobprodcus383.vsblob.vsassets.io
  • Triggering command: /home/REDACTED/work/testfx/testfx/.dotnet/dotnet msbuild /m /nologo /clp:Summary /v:minimal /nr:true /warnaserror /p:TreatWarningsAsErrors=true /p:ContinuousIntegrationBuild=false /home/REDACTED/work/testfx/testfx/artifacts/toolset/restore.proj /t:__WriteToolsetLocation /clp:ErrorsOnly;NoSummary /p:__ToolsetLocationOutputFile=/home/REDACTED/work/testfx/testfx/artifacts/toolset/10.0.0-beta.25313.2.txt (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[Evangelink]

Let's also add the codefix related to this analyzer please.

[Copilot]

Let's also add the codefix related to this analyzer please.

Added codefix for the UseCooperativeCancellationForTimeout analyzer. The codefix automatically transforms [Timeout] attributes to include CooperativeCancellation = true. Includes comprehensive test coverage for all scenarios. Commit 6615e56.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• cflvsblobprodcus383.vsblob.vsassets.io
  • Triggering command: /home/REDACTED/work/testfx/testfx/.dotnet/dotnet msbuild /m /nologo /clp:Summary /v:minimal /nr:true /warnaserror /p:TreatWarningsAsErrors=true /p:ContinuousIntegrationBuild=false /home/REDACTED/work/testfx/testfx/artifacts/toolset/restore.proj /t:__WriteToolsetLocation /clp:ErrorsOnly;NoSummary /p:__ToolsetLocationOutputFile=/home/REDACTED/work/testfx/testfx/artifacts/toolset/10.0.0-beta.25313.2.txt (dns block)
  • Triggering command: ./.dotnet/dotnet build src/Analyzers/MSTest.Analyzers/MSTest.Analyzers.csproj --verbosity quiet (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

[Evangelink]

The timeout attribute can be also specified on all fixture methods (e.g. ClassInitialize) so please remove the check for TestMethodAttribute, checking only TimeoutAttribute is enough. There is another rule to ensure the TimeoutAttribute is used at the right location.

Please update codefixer and tests!

[Copilot]

The timeout attribute can be also specified on all fixture methods (e.g. ClassInitialize) so please remove the check for TestMethodAttribute, checking only TimeoutAttribute is enough. There is a...

Removed the check for TestMethodAttribute - the analyzer now triggers on any method with [Timeout] attribute, including all fixture methods (ClassInitialize, AssemblyInitialize, etc.). Updated tests to cover all fixture method scenarios and updated the codefix accordingly. Commit 8fc728a.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• cflvsblobprodcus383.vsblob.vsassets.io
  • Triggering command: /home/REDACTED/work/testfx/testfx/.dotnet/dotnet msbuild /m /nologo /clp:Summary /v:minimal /nr:true /warnaserror /p:TreatWarningsAsErrors=true /p:ContinuousIntegrationBuild=false /home/REDACTED/work/testfx/testfx/artifacts/toolset/restore.proj /t:__WriteToolsetLocation /clp:ErrorsOnly;NoSummary /p:__ToolsetLocationOutputFile=/home/REDACTED/work/testfx/testfx/artifacts/toolset/10.0.0-beta.25313.2.txt (dns block)
  • Triggering command: ./.dotnet/dotnet build src/Analyzers/MSTest.Analyzers/MSTest.Analyzers.csproj --verbosity quiet (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list