Issue with StaticWebAssets in Blazor WebAssembly Hosted on .NET 9.0

[Solbstr]

I encountered a significant issue while building my Blazor WebAssembly Hosted project after migrating to .NET 9.0.101. The build fails with over 200 errors related to missing .gz assets. These errors indicate that .gz files are being searched for in the compressed folder, even though these files were not added or generated during the build process.

The errors are triggered by Microsoft.NET.Sdk.StaticWebAssets.Compression.targets.

[javiercn]

@Solbstr thanks for contacting us.

Do you have a repro you can share?

[Solbstr]

Hi @javiercn,

I’ve been working on a fitness app for five years, and after migrating the project to .NET 9.0.101, I encountered build errors related to missing .gz assets. After extensive testing and troubleshooting, I discovered the root cause of the issue.

The problem was caused by the following line in the .csproj file of the Client project:

<PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">
    <BlazorWebAssemblyLoadAllGlobalizationData>true</BlazorWebAssemblyLoadAllGlobalizationData>
    <BlazorWebAssemblyLoadGlobalizationDataForCultures>en-US;nb-NO</BlazorWebAssemblyLoadGlobalizationDataForCultures>
    <InvariantGlobalization>false</InvariantGlobalization>
    <CompressionEnabled>false</CompressionEnabled> <!-- This line caused the issue -->
    <BlazorEnableTimeZoneSupport>true</BlazorEnableTimeZoneSupport>
</PropertyGroup>

When I commented out or removed the CompressionEnabled property, the project built successfully. It seems this property, when explicitly set to false, causes .gz asset references to be handled incorrectly during the build process.

[javiercn]

@Solbstr thanks for the additional details.

That helps a lot, I'm able to reproduce it now.

[javiercn]

It doesn't seem related to a fix that we took for servicing, but we are investigating, maybe something else has changed. From what I can see on the binlog, the asset does not contain the correct definition in this case.

The asset '\obj\Debug\net9.0\compressed\ni2t65rtxn-8fnvbemkr6.gz' can not be found at any of the searched locations '\bin\Debug\net9.0\wwwroot\_framework\System.Data.wasm' and '\bin\Debug\net9.0\wwwroot\_framework\System.Data.wasm'.

[javiercn]

Ok, I figured it out.

Things go wrong in UpdateExternallyDefinedStaticWebAssets as it's changing the original item spec

[javiercn]

This line is the culprit
https://github.com/dotnet/sdk/blob/ff1e3c8624fbbad8ea4e126bd98ec9cfc2dbbc9e/src/StaticWebAssetsSdk/Tasks/Data/StaticWebAs
set.cs#L183

[javiercn]

Just checked and it reproduces on 9.0 RTM, so it's a bug, but not a regression in any patch fix.