dotnet format doesn't write to disk after updating to dotnet SDK 9.0.200

[ferrarimarco]

Describe the bug

dotnet format doesn't write formatting changes back to the file after updating the dotnet SDK to 9.0.200. It works up to 9.0.102.

To Reproduce

1. Create a file named csharp_bad_01.cs in the current working directory with the following contents (ensure to respect spaces and blank lines):

using System;

namespace HelloWorld {
  class Program {
    static void Main(string[] args) {
      Console.WriteLine("Hello World");
    }
  }
}

1. Run docker run --rm -it --entrypoint /bin/ash -v $(pwd):/app mcr.microsoft.com/dotnet/sdk:9.0.200-alpine3.21

2. Run cd /app

3. Hash the content of the file: sha256sum csharp_bad_01.cs. Output:

813c093e202045f5f6c88ab88e988aafd2120feb6479b0e667717714d1e4e39d  csharp_bad_01.cs

1. Run dotnet format whitespace --folder --exclude / --include csharp_bad_01.cs -v diag --verify-no-changes. Output:

  Formatting code files in workspace '/app/'.
  Loading workspace.
  Complete in 1271ms.
  Determining formattable files.
  Complete in 191ms.
  Running formatters.
/app/csharp_bad_01.cs(3,21): error WHITESPACE: Fix whitespace formatting. Replace 1 characters with '\n'. [/app//]
/app/csharp_bad_01.cs(4,3): error WHITESPACE: Fix whitespace formatting. Insert '\s\s'. [/app/]
/app/csharp_bad_01.cs(4,16): error WHITESPACE: Fix whitespace formatting. Replace 1 characters with '\n\s\s\s\s'. [/app/]
/app/csharp_bad_01.cs(5,5): error WHITESPACE: Fix whitespace formatting. Insert '\s\s\s\s'. [/app/]
/app/csharp_bad_01.cs(5,36): error WHITESPACE: Fix whitespace formatting. Replace 1 characters with '\n\s\s\s\s\s\s\s\s'. [/app/]
/app/csharp_bad_01.cs(6,7): error WHITESPACE: Fix whitespace formatting. Insert '\s\s\s\s\s\s'. [/app/]
/app/csharp_bad_01.cs(7,5): error WHITESPACE: Fix whitespace formatting. Insert '\s\s\s\s'. [/app/]
/app/csharp_bad_01.cs(8,3): error WHITESPACE: Fix whitespace formatting. Insert '\s\s'. [/app/]
  Complete in 436ms.
  Formatted code file '/app/csharp_bad_01.cs'.
  Formatted 1 of 1 files.
  Format complete in 1899ms.
/app/test/linters/csharp # exit
exit status 2

1. Run dotnet format whitespace --folder --exclude / --include csharp_bad_01.cs -v diag. Output:

  Formatting code files in workspace '/app/'.
  Loading workspace.
  Complete in 1257ms.
  Determining formattable files.
  Complete in 191ms.
  Running formatters.
  Complete in 467ms.
  Formatted code file '/app/csharp_bad_01.cs'.
  Formatted 1 of 1 files.
  Format complete in 1978ms.

1. Hash the content of the file: sha256sum csharp_bad_01.cs, observing that it has the same hash as before, and the same content. Output:

813c093e202045f5f6c88ab88e988aafd2120feb6479b0e667717714d1e4e39d  csharp_bad_01.cs

If you repeat the steps described above using the 9.0.102-alpine3.21 container image, you can observe that dotnet format correctly writes the formatted file.

Exceptions (if any)

Further technical details

• Include the output of dotnet --info:

/ # dotnet --info
.NET SDK:
 Version:           9.0.200
 Commit:            90e8b202f2
 Workload version:  9.0.200-manifests.b4a8049f
 MSBuild version:   17.13.8+cbc39bea8

Runtime Environment:
 OS Name:     alpine
 OS Version:  3.21
 OS Platform: Linux
 RID:         linux-musl-x64
 Base Path:   /usr/share/dotnet/sdk/9.0.200/

.NET workloads installed:
There are no installed workloads to display.
Configured to use loose manifests when installing new manifests.

Host:
  Version:      9.0.2
  Architecture: x64
  Commit:       80aa709f5d

.NET SDKs installed:
  9.0.200 [/usr/share/dotnet/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 9.0.2 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 9.0.2 [/usr/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

Also, not sure if #46780 is related to this.

[ghost]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[ghost]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[jdaigle]

I've run into this exact same issue. Reproduced on MacOS.

[edvilme]

Hello @dotnet/roslyn-ide do we have some information on this?
cc @sharwell

[JoeRobich]

This issue is caused by the same null Encoding Roslyn bug as #46780. It only affects saving files when using the --folder option.

sdk/src/BuiltInTools/dotnet-format/Workspaces/FolderWorkspace.cs

Lines 51 to 59 in 9c64e2f

	protected override void ApplyDocumentTextChanged(DocumentId documentId, SourceText text)
	{
	var document = CurrentSolution.GetDocument(documentId);
	if (document?.FilePath != null && text.Encoding != null)
	{
	SaveDocumentText(documentId, document.FilePath, text, text.Encoding);
	OnDocumentTextChanged(documentId, text, PreservationMode.PreserveValue);
	}
	}

A fix has been merged that should flow into the 9.0.2xx SDK (see dotnet/roslyn#77362). I have confirmed that the issue is fixed in the nightly .NET 10 build.

[JoeRobich]

Verified that the nightly 9.0.300 build works, also found the insertion of the fix into the 9.0.2xx branch (See #46931)

[edvilme]

Thank for the confirmation @JoeRobich