[Known Build Error] Blazor WASM template tests fail with NU1603: DevServer 10.0.6-ci not found, 10.0.6 resolved instead

[lewing]

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1324975
Build error leg or test failing: Build Test: Windows Server x64
Pull request: #65695

Error Message

{
  "ErrorPattern": "NU1603.*DevServer.*was not found",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Description

Blazor WASM template tests fail with NU1603 when a darc feed (from VMR codeflow) contains a stable DevServer package that outranks the locally-built prerelease (-ci) package. NuGet considers stable versions (e.g. 10.0.6) higher than prerelease versions (e.g. 10.0.6-ci), so it resolves to the stable version, triggering NU1603 ("exact version not found"). Since WarningsAsErrors is enabled, this becomes a fatal error.

This will recur on every servicing patch version — not just 10.0.6 — whenever the VMR official build publishes a stable DevServer package to a darc feed that is then added to NuGet.config via codeflow.

Failing tests:

• BlazorWasmStandaloneTemplate_Works(Chromium)
• BlazorWasmStandalonePwaTemplate_Works(Chromium)
• BlazorWasmStandaloneTemplate_AzureActiveDirectoryTemplate_Works

Known issue matching note: The AzureActiveDirectoryTemplate_Works test reports an empty error message in AzDO test results, so Build Analysis cannot match it. The other two tests include the NU1603 error in their error message and will match. The overall build error in the AzDO timeline only says Tests failed: ...Templates.Blazor.Tests_net10.0_x64.html which is too generic to use as a pattern without risking false matches on unrelated Blazor test failures.

Root cause: VMR official builds produce stable-versioned packages published to darc feeds. These feeds are added to NuGet.config via codeflow PRs. The template stamps a -ci prerelease version as the DevServer version (correct for CI builds), but the darc feed has the stable version (semver-higher), causing NuGet to resolve to it and emit NU1603.

First seen: Build 1324271 (PR #65687, codeflow from VMR build 304915, merged Mar 6 2026).

Proposed fix: Pin the exact DevServer package version in the test infrastructure (e.g., [x.y.z-ci] exact version range) so the locally-built package is always used during template tests. The shipped template should continue using >= semantics for customers.

Report

Build	Definition	Test	Pull Request
1329520	dotnet/aspnetcore	BlazorTemplates.Tests.BlazorWasmTemplateTest.BlazorWasmStandalonePwaTemplate_Works(browserKind: Chromium)	#65721
1327578	dotnet/aspnetcore	BlazorTemplates.Tests.BlazorWasmTemplateTest.BlazorWasmStandalonePwaTemplate_Works(browserKind: Chromium)	#65718
1324975	dotnet/aspnetcore	BlazorTemplates.Tests.BlazorWasmTemplateTest.BlazorWasmStandalonePwaTemplate_Works(browserKind: Chromium)	#65695

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	3	3

[lewing]

Fix Options

Option 1: Pin exact version in test infrastructure (most correct)

Pass the DevServer version through PrepareForTest.targets into Directory.Build.props.in and add a PackageReference Update with an exact version range:

PrepareForTest.targets — add MicrosoftAspNetCoreComponentsWebAssemblyDevServerVersion to the Properties passed to GenerateFileFromTemplate for Directory.Build.props.in.

Directory.Build.props.in — add:

<ItemGroup>
  <PackageReference Update="Microsoft.AspNetCore.Components.WebAssembly.DevServer" 
                    Version="[${MicrosoftAspNetCoreComponentsWebAssemblyDevServerVersion}]" />
</ItemGroup>

This forces NuGet to use the exact locally-built version (10.0.6-ci) and reject the stable 10.0.6 from darc feeds. The shipped template keeps >= semantics for customers.

Pros: Precise, only affects DevServer, ensures the locally-built package is always used.
Cons: Requires plumbing a new property through PrepareForTest.targets. May need to repeat if other packages hit the same issue.

Option 2: Suppress NU1603 in template test projects

Add <NoWarn>$(NoWarn);NU1603</NoWarn> to Directory.Build.targets.in (or Directory.Build.props.in).

Pros: Simple one-line change, no property plumbing needed.
Cons: Suppresses ALL NU1603 warnings in template tests, potentially hiding real version mismatch issues.

Option 3: Suppress NU1603 only for DevServer

Add to Directory.Build.targets.in:

<ItemGroup>
  <PackageReference Update="Microsoft.AspNetCore.Components.WebAssembly.DevServer" NoWarn="NU1603" />
</ItemGroup>

Pros: Targeted suppression, no property plumbing.
Cons: Doesn't guarantee the locally-built package is used — NuGet will silently pick the stable version from the darc feed, which may cause subtle test behavior differences.

Context

• TreatWarningsAsErrors is set in eng/tools/GenerateFiles/Directory.Build.props.in (line 5), which the test templates import
• The locally-built 10.0.6-ci.nupkg IS in artifacts/packages/Release/Shipping/ and IS in RestoreAdditionalProjectSources
• NuGet picks stable 10.0.6 from darc feeds because stable > prerelease in SemVer
• This will recur every time a new servicing patch ships and the stable version appears on darc feeds