`--no-parallel` test option breaks debugging

[SimplyDanny]

Describe the bug

Disabling parallel testing in settings.json with

"swift.additionalTestArguments": [
    "--no-parallel"
]

runs tests sequentially as intended. However, debugging tests doesn't work anymore as --no-parallel is passed to swift build where it is invalid.

To Reproduce
Steps to reproduce the behavior:

1. Configure the argument in settings.json.
2. Running tests works.
3. Debugging tests fails while building due to the unknown option --no-parallel.

Expected behavior
The option should not be passed to build steps.

Environment

• OS: macOS 15.6.1
• Swift version: swift-driver version: 1.127.14.1 Apple Swift version 6.2 (swiftlang-6.2.0.19.9 clang-1700.3.19.1)
• Visual Studio Code version: 1.104.2
• vscode-swift version: 2.11.20250806

[plemarquand]

Thanks for the report! I've merged a fix that will pass all acceptable flags to the swift build invocation made before debugging. All the additionalTestFlags are still passed to the binary on launch, so things like --no-parallel are omitted from the build, but passed to the binary and work as you'd expect now.

[SimplyDanny]

That was fast. Thanks @plemarquand!