[Blazor] GenerateE2EManifest task crashes with MissingMethodException on JsonObjectInfoValues<T>.set_PolymorphismOptions in Preview 5

[danroth27]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

When the GenerateE2EManifest MSBuild task from Microsoft.AspNetCore.Components.Testing 11.0.0-preview.5.26276.113 (latest on the dotnet11 public feed) runs under SDK 11.0.100-preview.5.26272.118, it crashes with a MissingMethodException:

error MSB4018: The "GenerateE2EManifest" task failed unexpectedly.
System.MissingMethodException: Method not found: 'Void System.Text.Json.Serialization.Metadata.JsonObjectInfoValues`1.set_PolymorphismOptions(System.Text.Json.Serialization.Metadata.JsonPolymorphismOptions)'.
   at Microsoft.AspNetCore.Components.Testing.Tasks.E2EManifestJsonContext.Create_E2EManifestModel(JsonSerializerOptions options)
   at Microsoft.AspNetCore.Components.Testing.Tasks.E2EManifestJsonContext.global::System.Text.Json.Serialization.Metadata.IJsonTypeInfoResolver.GetTypeInfo(Type type, JsonSerializerOptions options)
   at System.Text.Json.JsonSerializerOptions.GetTypeInfoNoCaching(Type type)
   at System.Text.Json.JsonSerializerOptions.CachingContext.CreateCacheEntry(Type type, CachingContext context)
--- End of stack trace from previous location ---
   at System.Text.Json.JsonSerializerOptions.GetTypeInfoInternal(...)
   at System.Text.Json.JsonSerializerOptions.GetTypeInfo(Type type)
   at Microsoft.AspNetCore.Components.Testing.Tasks.E2EManifestJsonContext.get_E2EManifestModel()
   at Microsoft.AspNetCore.Components.Testing.Tasks.GenerateE2EManifest.Execute()

E2EManifestJsonContext is a JsonSerializerContext source-generated inside Microsoft.AspNetCore.Components.Testing.Tasks.dll (netstandard2.0). The generated Create_E2EManifestModel calls JsonObjectInfoValues<T>.set_PolymorphismOptions, which is not present on the System.Text.Json assembly the MSBuild host loads at runtime. The result is that every build that consumes this package fails the GenerateE2EManifest task.

This is a different failure mode than #66617 — that issue was the task being silently skipped due to a path mismatch in preview.4. In preview.5 the path resolution has been fixed (the task now executes), but the source generator's emitted code references an STJ surface that does not exist in the SDK's STJ.

Expected Behavior

GenerateE2EManifest runs to completion and produces *.e2e-manifest.json next to the test DLL.

Steps To Reproduce

Minimal repro project layout (the consuming pattern from dotnet/aspnetcore's test infrastructure, reduced):

<!-- AppRepro.csproj -->
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net11.0</TargetFramework>
    <OutputType>Exe</OutputType>
    <IsPackable>false</IsPackable>
    <IsTestProject>false</IsTestProject>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Components.Testing" Version="11.0.0-preview.5.26276.113" />
  </ItemGroup>

  <ItemGroup>
    <ProjectReference Include="..\BlazorApp\BlazorApp.csproj">
      <E2EApp>true</E2EApp>
    </ProjectReference>
  </ItemGroup>
</Project>

(Where BlazorApp.csproj is any Blazor Web App.)

dotnet build fails with the MissingMethodException above. A full real-world repro is at https://github.com/danroth27/AspNetCore11Samples/tree/main/BlazorFeatures.E2E.Tests.

Note: that project also has a <_E2ETasksAssembly> override pointing at tasks/netstandard2.0/Microsoft.AspNetCore.Components.Testing.Tasks.dll as a workaround for #66617. Removing it does not change the outcome in preview.5 — the targets file's own probe also resolves the task DLL, executes it, and hits the same STJ crash.

Environment

.NET SDK:            11.0.100-preview.5.26272.118
Microsoft.AspNetCore.Components.Testing: 11.0.0-preview.5.26276.113 (dotnet11 feed)
Host runtime STJ:    System.Text.Json 11.0.0-preview.5.26272.118
Task assembly:       tasks/netstandard2.0/Microsoft.AspNetCore.Components.Testing.Tasks.dll
                     (ProductVersion 11.0.0-preview.5.26276.113)
OS:                  Windows 11

Anything else?

Likely root cause: the JsonSerializerContext source generator that produced E2EManifestJsonContext was run against an older System.Text.Json and emitted a set_PolymorphismOptions setter call. In the STJ that ships with the .NET 11 Preview 5 runtime, JsonObjectInfoValues<T>.PolymorphismOptions no longer exposes a setter at that signature, so the generated code throws MissingMethodException at JIT time as soon as the context is touched.

If that diagnosis is correct, regenerating the task assembly's source-gen against current STJ — or pinning the task to a known-compatible STJ — should resolve it.

Impact: any test project that takes a PackageReference on Microsoft.AspNetCore.Components.Testing 11.0.0-preview.5.26276.113 from the public dotnet11 feed cannot build, so consumers of the public preview cannot run Blazor E2E tests on Preview 5.

[github-actions]

Triage Summary

Area: area-blazor — The issue is in Microsoft.AspNetCore.Components.Testing's MSBuild task assembly (GenerateE2EManifest), which is part of the Blazor E2E testing infrastructure under src/Components/.

Type: Bug — A concrete MissingMethodException crash is reproducible when the task executes under the Preview 5 SDK. The task DLL was source-generated against an older STJ whose JsonObjectInfoValues<T>.PolymorphismOptions API shape differs from what ships in Preview 5.

Regression Info

• Previously working version: 11.0.0-preview.4 (the task was silently skipped due to [Blazor] Microsoft.AspNetCore.Components.Testing: GenerateE2EManifest task silently skipped because tasks/ folder is not where the targets file looks #66617, so it never reached execution)
• Broken since: 11.0.0-preview.5.26276.113 (path resolution was fixed, but the task now crashes on execution)
• The fix for [Blazor] Microsoft.AspNetCore.Components.Testing: GenerateE2EManifest task silently skipped because tasks/ folder is not where the targets file looks #66617 (correcting the task assembly probe path) exposed this secondary bug: the source-generated E2EManifestJsonContext references JsonObjectInfoValues<T>.set_PolymorphismOptions, which no longer exists in the Preview 5 STJ, causing an MSB4018 fatal task failure.

Potential Duplicates

• [Blazor] Microsoft.AspNetCore.Components.Testing: GenerateE2EManifest task silently skipped because tasks/ folder is not where the targets file looks #66617 — Related predecessor issue (task silently skipped in preview.4 due to path mismatch); this issue is the follow-on bug exposed after that fix. Not a duplicate — distinct failure mode.

Notes

• Root cause is an STJ source-generator binary skew: the task DLL was compiled/source-generated against a version of System.Text.Json whose JsonObjectInfoValues<T> had a set_PolymorphismOptions setter, but that setter was removed or refactored in the Preview 5 runtime STJ.
• Fix: re-run STJ source generation against the current Preview 5 STJ, or restructure E2EManifestJsonContext to avoid the dropped API.
• Impact is broad: all external consumers of Microsoft.AspNetCore.Components.Testing 11.0.0-preview.5.26276.113 from the public dotnet11 feed are blocked from building Blazor E2E test projects.

Generated by Issue Triage Agent for dotnet/aspnetcore for issue #66878 · sonnet46 730.1K · ◷

[oroztocil]

This issue might be transient and should get fixed in a new SDK build.

@eiriktsarpalis Does this look familiar?

[eiriktsarpalis]

JsonObjectInfoValues<T>.PolymorphismOptions is recently added API, so the error suggests to me that an older version of STJ.dll is being referenced at run time.