`SdkContentTests.CompareMsftToSbTemplatePackageVersions` fails: 11.0 MSTest templates aren't valid standalone XML

[mthalman]

Summary

The scheduled source-build-sdk-diff-tests pipeline has been failing daily on refs/heads/main since 2026-04-29. The test Microsoft.DotNet.SourceBuild.Tests.SdkContentTests.CompareMsftToSbTemplatePackageVersions fails on
all 6 source-build legs (SB_AlmaLinux8, SB_Alpine323, SB_CentOSStream10, SB_Fedora43, SB_Ubuntu2404 x64, SB_Ubuntu2404Arm64 arm64) while attempting to parse an MSTest C# template project file as XML.
release/10.0.4xx is unaffected.

Build Information

• Build: internal/2974874 — source-build-sdk-diff-tests 20260514.2
• Pipeline: \dotnet\dotnet\source-build-sdk-diff-tests (definition 1231)
• Branch: refs/heads/main
• Commit: 88f54a26a932b6535047d5ddd4a58370ca356664
• Failing leg: SB_AlmaLinux8_Offline_MsftSdk_x64 → task Run Tests (and the same task on all 5 other SB legs)
• Recurring since: 2026-04-29 (Build 2963174) — 12+ consecutive scheduled failures on main

Error Details

[xUnit.net 00:00:55.10]     Microsoft.DotNet.SourceBuild.Tests.SdkContentTests.CompareMsftToSbTemplatePackageVersions [FAIL]
[xUnit.net 00:00:55.10]       System.Exception : Failed to parse project file 'content/MSTest-CSharp/Company.TestProject1.csproj' from package archive.
[xUnit.net 00:00:55.10]       ---- System.Xml.XmlException : The 'Project' start tag on line 2 position 2 does not match the end tag of 'PropertyGroup'. Line 22, position 5.
   at Microsoft.DotNet.SourceBuild.Tests.SdkContentTests.GetPackageReferencesFromProjectFile(ZipArchiveEntry entry) in test/Microsoft.DotNet.SourceBuild.Tests/SdkContentTests.cs:line 228
   at Microsoft.DotNet.SourceBuild.Tests.SdkContentTests.GetTemplatePackageVersions(...) in SdkContentTests.cs:line 197
   at Microsoft.DotNet.SourceBuild.Tests.SdkContentTests.CompareMsftToSbTemplatePackageVersions() in SdkContentTests.cs:line 148

Root Cause

This is a two-factor failure: a latent template bug exposed by a test-hardening change.

Factor 1 — Two 11.0 templates aren't valid standalone XML

Microsoft.DotNet.Common.ProjectTemplates.11.0 (introduced 2025-12-22)
contains two templates whose <!--#if (UseMSTestSdk)--> / <!--#else--> / <!--#endif--> directives wrap structurally unbalanced XML — each branch contains its own <Project> element and </PropertyGroup> close tag:

• content/MSTest-CSharp/Company.TestProject1.csproj
• content/Playwright-MSTest-CSharp/Company.TestProject1.csproj

The XML parser ignores the #if markers (they look like comments) and sees a single <Project> with one <PropertyGroup> opening and two </PropertyGroup> closes. I verified by parsing every *.csproj under
src/sdk/template_feed/ with .NET's XML parser — only these two fail.

The MSTest-CSharp file is reported in the log because GetPackageReferencesFromProjectFile throws on the first failure; the Playwright variant will be the next failure once MSTest is fixed.

Factor 2 — Test now throws on parse failure (was silent)

dotnet/dotnet#6350 ("Fix EF Core template versions in source-build and add test") added CompareMsftToSbTemplatePackageVersions and changed GetPackageReferencesFromProjectFile to
throw on XmlException instead of returning an empty dictionary:

- catch
+ catch (XmlException ex)
  {
-     return versions;
+     throw new Exception($"Failed to parse project file '{entry.FullName}' from package archive.", ex);
  }

This was an intentional improvement (silent skips would have hidden the very EF Core version drift the PR was trying to detect), but it surfaced the latent template-parse bug the next time the scheduled pipeline ran.

Timeline

Date (UTC)	Build	Branch	Result
2025-12-22	—	dotnet/sdk	Broken 11.0 MSTest templates committed (latent — old test silently skipped)
2026-04-28 12:00	2962204	main	succeeded (ran before PR #6350 merge at 20:02 UTC)
2026-04-28 20:02	—	main	PR #6350 merged → test now throws
2026-04-29 12:00	2963174	main	first failure
2026-04-29 → present	(12+ runs)	main	all failed with identical error
2026-05-14 12:00	2974871	release/10.0.4xx	succeeded (uses ProjectTemplates.10.0, not affected)

Suggested Fix

Make GetPackageReferencesFromProjectFile tolerant of template-engine directives, since *.csproj files in template-feed nupkgs are template source, not strict XML. Either:

1. Preprocess: strip <!--#if ... -->, <!--#else-->, <!--#endif--> lines before XDocument.Load, or
2. Tolerant scan: extract <PackageReference Include="..." Version="..." /> with a regex-based scan that doesn't require a balanced document.

Both approaches keep the test's coverage on these templates (so version drift in MSTest/Playwright is still caught) while accepting that template source isn't strict XML.

Alternative — fix the templates so each #if branch is independently XML-balanced — would require duplicating large blocks because the two branches use different Project Sdk= values, and is a change in dotnet/sdk (and possibly
dotnet/templating).