High CPU usage and autocompletion breaking on Windows

[tomwyr]

Describe the bug
Opening a new file and just changing language mode to Swift causes multiple cores of the CPU to kick in and never stop, even when the source file is still empty. Also, the autocompletion doesn't seem to work and, as soon as there's an error introduced to the code, the analyzer hangs at displaying that particular error unless I restart vscode or the LSP.

Expected behavior
Autocompletion doesn't break and CPU usage is low when LSP has nothing to be busy with.

Environment

• OS: Windows 11
• Swift version: compnerd.org Swift version 5.9 (swift-5.9-RELEASE) Target: x86_64-unknown-windows-msvc
• Visual Studio Code version: 1.82.2
• vscode-swift version: 1.5.2

Additional context
The red lines on the screenshots mark the moment where language mode is changed to Swift and (I assume) the vscode extension gets activated.

[adam-fowler]

@compnerd have you seen anything like this?

[Shockah]

Having the same issue, straight after setting up Swift and VSCode. Killing the sourcekit-lsp.exe process unfreezes autocompletion, but any further change has the same result.

[natinusala]

I have the same issue on Windows 10 here.

I also have a weird problem where the SourceKit LSP process locks up C files (including headers) in my project and I can't edit them anymore unless I fully exit vscode (which kills sourcekit). I don't know if it's related.

[adam-fowler]

I also have a weird problem where the SourceKit LSP process locks up C files (including headers) in my project and I can't edit them anymore unless I fully exit vscode (which kills sourcekit). I don't know if it's related.

This will be unrelated. Probably an issue you should post to sourcekit-lsp repo.

@tomwyr Similarly this performance issue should be bugged on sourcekit-lsp repo

[icnahom]

The issue does not occur in Swift 5.8.1.

[adam-fowler]

The issue does not occur in Swift 5.8.1.

Can anyone else verify this please?

[tomwyr]

Can confirm the CPU usage is back to normal in Swift 5.8.1. Also I tested the latest version 5.9.1 on a different laptop and the problem persists there as well.

[adam-fowler]

This almost certainly is a SourceKit-LSP issue, so I have reported it there swiftlang/sourcekit-lsp#982

[adam-fowler]

Closing as related SourceKit-LSP issue has been closed