Clearing NuGet package local cache breaks re-compiling file-based apps

[gorban]

Describe the bug

Clearing local NuGet package cache breaks re-compiling file-based apps.

To Reproduce

1. Add NuGet package source (at least until 10.0.1 packages exist on nuget.org):
   dotnet nuget add source https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet10/nuget/v3/index.json -n dotnet10
2. Create a whatever.cs file with execute (chmod +x whatever.cs) with below contents.
3. Execute it to compile and run the first time:
   ./whatever.cs
4. Clear NuGet package local cache:
   dotnet nuget locals all -c
5. At this point, executing ./whatever.cs still works fine (cached binary)
6. Make any slight tweak to the code, e.g. the string passed to WriteLine: Console.WriteLine("I broke it!");
7. Now, trying to rebuild / execute will fail:
   ./whatever.cs

Error:

error CS0006: Metadata file '/Users/bruck/.nuget/packages/microsoft.net.illink.tasks/10.0.0-rtm.25513.102/analyzers/dotnet/cs/ILLink.CodeFixProvider.dll' could not be found
error CS0006: Metadata file '/Users/bruck/.nuget/packages/microsoft.net.illink.tasks/10.0.0-rtm.25513.102/analyzers/dotnet/cs/ILLink.RoslynAnalyzer.dll' could not be found

The build failed. Fix the build errors and run again.

Code:

#!/usr/bin/env dotnet
#:property TargetFramework=net10.0
#:property RuntimeFrameworkVersion=10.0.0-rtm.25513.102
Console.WriteLine("Hello from a .NET script!");

Exceptions (if any)

Further technical details

.NET SDK:
Version: 10.0.101
Commit: e17b0d08de
Workload version: 10.0.100-manifests.c57ac48b
MSBuild version: 18.0.3+e17b0d08d

Runtime Environment:
OS Name: Mac OS X
OS Version: 15.7
OS Platform: Darwin
RID: osx-arm64
Base Path: /usr/local/share/dotnet/sdk/10.0.101/

.NET workloads installed:
There are no installed workloads to display.
Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
Version: 10.0.1
Architecture: arm64
Commit: e17b0d08de

.NET SDKs installed:
8.0.407 [/usr/local/share/dotnet/sdk]
8.0.411 [/usr/local/share/dotnet/sdk]
10.0.101 [/usr/local/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 8.0.14 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.17 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 10.0.1 [/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 8.0.14 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.17 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]
Microsoft.NETCore.App 10.0.1 [/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Other architectures found:
None

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

[gorban]

Maybe clearing the NuGet package cache should also clear out whatever is getting cached from the last build of any file-based apps?

[jjonescz]

Thanks for reporting this. There is an optimization to recompile using C# compiler only (skipping MSBuild, so also restore) on subsequent re-runs of file-based apps. You can force full recompilation using dotnet run app.cs --no-cache (or dotnet build app.cs).

I don't think the NuGet command can reliably find and clear the file-based app cache. Instead, the optimization logic could check that the referenced DLLs still exist and fallback to full build if not (we could also do that only if the optimized compilation fails; to not slow down the fast path).