C# - Upgrade from .sln to .slnx solution files

[Joy-less]

The .sln format for C# solution files (containing multiple projects) is a very old and proprietary format from 1997.
Here's an example:

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio Version 17
VisualStudioVersion = 17.8.34322.80
MinimumVisualStudioVersion = 10.0.40219.1
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "RecordTypes", "RecordTypes.csproj", "{3322D5B8-4E43-42B6-BA18-6F6188ED8801}"
EndProject
Global
 GlobalSection(SolutionConfigurationPlatforms) = preSolution
  Debug|Any CPU = Debug|Any CPU
  Release|Any CPU = Release|Any CPU
 EndGlobalSection
 GlobalSection(ProjectConfigurationPlatforms) = postSolution
  {3322D5B8-4E43-42B6-BA18-6F6188ED8801}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
  {3322D5B8-4E43-42B6-BA18-6F6188ED8801}.Debug|Any CPU.Build.0 = Debug|Any CPU
  {3322D5B8-4E43-42B6-BA18-6F6188ED8801}.Release|Any CPU.ActiveCfg = Release|Any CPU
  {3322D5B8-4E43-42B6-BA18-6F6188ED8801}.Release|Any CPU.Build.0 = Release|Any CPU
 EndGlobalSection
 GlobalSection(SolutionProperties) = preSolution
  HideSolutionNode = FALSE
 EndGlobalSection
 GlobalSection(ExtensibilityGlobals) = postSolution
  SolutionGuid = {AE1350F1-0A7D-41AD-8016-79BE8B49D945}
 EndGlobalSection
EndGlobal

In April 2024, Microsoft released an alternative solution format called .slnx, which uses XML, like .csproj files.

<Solution>
  <Project Path="RecordTypes.csproj" />
</Solution>

It would be ideal for Godot to support the new .slnx format when it is rolled out. Currently, Godot appears to be hardcoded to support only .sln files:

if os.path.exists(f"{project_name}.sln"):
        for line in open(f"{project_name}.sln", "r", encoding="utf-8").read().splitlines():
            if line.startswith('Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}")'):
                proj_uuid = re.search(
                    r"\"{(\b[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-\b[0-9a-fA-F]{12}\b)}\"$",
                    line,
                ).group(1)
            elif line.strip().startswith("SolutionGuid ="):
                sln_uuid = re.search(
                    r"{(\b[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-\b[0-9a-fA-F]{12}\b)}", line
                ).group(1)
                break

private const string _projectDeclaration =
@"Project(""{{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}}"") = ""{0}"", ""{1}"", ""{{{2}}}""
EndProject";

If Godot switched to only support .slnx files, a lot of this proprietary parsing mess code could be removed and replaced with an XML parser.

Additionally, the developer experience when manually editing the .sln file will be improved, for example when renaming a project it is often necessary to modify the .sln file.

• Now supported by msbuild: [Feature Request]: Support building the new Visual Studio solution file format (.slnx) dotnet/msbuild#10266
• Support pending for VSCode: Feature request: XML Solution (SLNX) workflow dotnet/vscode-csharp#7048

Note that .slnx seems to be intended for .NET 9.0, so it might be best to wait a bit. Consider this a long-term discussion to be revisited in the future.

[raulsntos]

There is already an approved PR (queued for 4.6) to support .slnx solution files:

• Fix: Correct Solution file load for GodotSharp godot#106031

After that, you'll be able to upgrade your .sln files to .slnx with the dotnet sln migrate command.

Using .slnx by default can't happen until most IDEs have decent support. It doesn't seem like VSCode is quite there yet, which would affect a big chunk of C# users (me included). And I'd rather wait for upstream templates to switch first (e.g.: dotnet new console).

Also, removing .sln support will likely never happen due to preserving compatibility. But the new Microsoft.VisualStudio.SolutionPersistence package implements all the parsing for both .sln and .slnx and we are already using it in the PR mentioned above, so there's no need to drop support for .sln.