Swift scripts update errors and warnings only after running

[F1248]

Describe the bug

Starting with version 2.4.0, warnings and errors in Swift scripts (standalone files) only update after running the Swift: Run Swift Script command but not after the file is modified or saved. In version 2.2.0, they update immediately when the file is modified.

To Reproduce

1. Create a new file Test.swift
2. Write some Swift code to the file that produces an error or warning, then save the file

let x: Int = "" // expected error: `Cannot convert value of type 'String' to specified type 'Int'`

3. The error only appears after running Swift: Run Swift Script
4. Replace "" with 0, then save the file again
5. The error only disappears after running Swift: Run Swift Script again

Environment

• OS: macOS Tahoe 26.0.1 (25A362)
• Swift version: swift-driver version: 1.127.14.1 Apple Swift version 6.2.1 (swiftlang-6.2.1.4.8 clang-1700.4.4.1)
• Visual Studio Code version: 1.105.1
• vscode-swift version: 2.12.0

[award999]

@ahoppen @bnbarham I would expect that running swift scripts performs some build which the LSP needs to even provide diagnostics?

[ahoppen]

We consider scripts to only have fallback build settings and thus don’t provide live issues. It’s been on the back of my mind for a while but I never really got to it, the tricky part is actually identifying a script, opposed to a Swift file in a project that we don’t have build system integration for. I’ve thought about looking for a Shebang or checking whether the current file is marked as executable.

If you ensure that SourceKit-LSP gets launched when working with these files, move this to sourcekit-lsp so we can take a look at it.