[dotnet format] 'Using directive is unnecessary' false positive in combination with Roslyn source generator

[BinaryTENSHi]

Describe the bug

Running dotnet format --verify-no-changes reports a error IDE0005: Using directive is unnecessary. false positive when the namespace is from a used class that was generated using a Roslyn source generator.

Running dotnet format removes the using {namespace}; which then leads to a compilation error afterward.

To Reproduce

I have created a minimal reproducible example here: https://github.com/BinaryTENSHi/dotnet-format-source-generator

1. Clone the repository
2. Run dotnet format --verify-no-changes

Running dotnet format and then dotnet build results in a compilation error.

Further technical details

.NET SDK 8.0.204

[Basyras]

Just start having the same problem... I would also note that the somewhat required dotnet build before dotnet format (to make sure all source generated file are present) doesn't help. I was already using net8 for some time but just recently updated to 8.0.204 SDK so the breaking must happened somewhere between those versions. Can repro locally and on our build machine via azure pipelines too (where same SDK version is installed.)

System Info:

Visual studio: 17.9.6
dotnet sdk: 8.0.204
dotnet runtime: 8.0.4

[suhrjo]

Having the same issue where dotnet format style removes used imports. When running dotnet format style -v detailed I get the output:

error IDE0005: Using directive is unnecessary

Which then removes the import. When running dotnet build after, I receive following output:

error CS0246: The type or namespace name 'X' could not be found (are you missing a using directive or an assembly reference?)

System Info:

dotnet runtime version: 8.0.6
dotnet CLI/SDK version: 8.0.301
running dotnet format with Windows Terminal