Unable to build project using VS 17.12.3: “DiscoverPrecompressedAssets” task failed unexpectedly

[fltrierweiler]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I've found a similar issue, but the exception there isn't the same (System.ArgumentException there and System.InvalidOperationException here) and that issue was closed without an answer, so I've decided to create a new one.

Basically, I'm unable to build an existing project that uses Blazor.BrowserExtension.Template. It used to work fine with version 17.11.35219.272.

Expected Behavior

Simply put, the project build should work without errors, as it used to do.

Steps To Reproduce

I've created a minimalistic project to showcase the issue. To reproduce the error, all that has to be done is to build the project.

Exceptions (if any)

Here's the error I get whenever I try to build the project using VS 17.12.3:

The "DiscoverPrecompressedAssets" task failed unexpectedly.
System.InvalidOperationException: Fingerprint for '...\ExtensionTest\ExtensionTest\obj\Debug\net8.0\browserextension\build\BackgroundWorker.js' is not defined.
   at Microsoft.AspNetCore.StaticWebAssets.Tasks.StaticWebAsset.Validate()
   at Microsoft.AspNetCore.StaticWebAssets.Tasks.StaticWebAsset.FromTaskItem(ITaskItem item)
   at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
   at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at Microsoft.AspNetCore.StaticWebAssets.Tasks.DiscoverPrecompressedAssets.Execute()
   at Microsoft.Build.BackEnd.TaskExecutionHost.Execute()
   at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext()

.NET Version

9.0.101

Anything else?

UPDATE: If I use SDK 8.0.404 and specify the version by adding a global.json to the solution folder, it actually works. Still no way to work with 9.0.101, though.

[MarcoMedrano]

I have the same issue building my maui app, your workaround is working (as I did not update my projects to dotnet 9):

global.json at root directory:

{
  "sdk": {
    "version": "8.0.206"
  }
}

[lofcz]

Hitting a similar error after upgrading from 8 to 9:

Error MSB4018 : The "DiscoverPrecompressedAssets" task failed unexpectedly.
System.ArgumentException: An item with the same key has already been added. Key: [path]\wwwroot\app.css
   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
   at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
   at System.Linq.Enumerable.SpanToDictionary[TSource,TKey](ReadOnlySpan`1 source, Func`2 keySelector, IEqualityComparer`1 comparer)
   at System.Linq.Enumerable.ToDictionary[TSource,TKey](IEnumerable`1 source, Func`2 keySelector, IEqualityComparer`1 comparer)
   at Microsoft.AspNetCore.StaticWebAssets.Tasks.DiscoverPrecompressedAssets.Execute()
   at Microsoft.Build.BackEnd.TaskExecutionHost.Execute()
   at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(TaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask)

In csproj, I have several files linked as:

<Content Include="..\[path]\wwwroot\**\app.scss">
    <Link>wwwroot\%(RecursiveDir)%(Filename)%(Extension)</Link>
    <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
    <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
</Content>

If I remove these links, the app builds but I can't use assets from the web project in the sln. This works as expected on 8.0.X

This is caused by:
https://github.com/dotnet/sdk/blob/1d3bf3b00bd92bc9eef62d56e97072425ea8d87f/src/StaticWebAssetsSdk/Tasks/Compression/DiscoverPrecompressedAssets.cs#L35C9-L35C106

ToDictionary() crashes if source contains duplicate keys.

[evgenyvalavin]

+1

[TechnoZamb]

bump!!!

[SirBirne]

This issue has persisted since SDK > 8.0.403 and I'm also looking forward to a fix.

[Lionel-Renaux]

As Github Copilot is being removed in 17.11, this is now beginning to be an issue as we cannot update without breaking our builds. The fix is in fact quite simple and already 2 PRs are open to fix it!

[LeeStevens318]

bump

[MiroslavJuhasCamea]

Hi, I'm hitting the same issue. VS Version 17.12.3. Project did not change for several months but suddenly it cannot be build.

The "DiscoverPrecompressedAssets" task failed unexpectedly. System.ArgumentException: An item with the same key has already been added. at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) at System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add)
at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable1 source, Func2 keySelector, Func2 elementSelector, IEqualityComparer1 comparer)
at Microsoft.AspNetCore.StaticWebAssets.Tasks.DiscoverPrecompressedAssets.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.d__26.MoveNext()`

[tbaggett-ebsco]

+1

We have also encountered this issue when attempting to update to .NET 9, based on Microsoft's recommendation that we do so in dotnet/maui#28475 to resolve the BlazorWebView component never being cleaned up when no longer needed in .NET 8.