Indexing-while-building shouldn't overwrite Package.resolved

[nkcsgexi]

Swift version

No response

Platform

No response

Editor

VSCode/Cursor

Description

SourceKit-LSP should pass --force-resolved-versions when invoking SwiftPM for background indexing. This ensures:

• SourceKit-LSP never writes to Package.resolved.
• Indexing operates against the package state already on disk, which is the correct behavior — indexing should be read-only.
• If packages are out of date, the resolution will fail, which is preferable to silently corrupting the resolved file.

This aligns with the principle that background indexing should be a read-only operation with respect to project state.

Steps to Reproduce

1. Configure a Swift package project that requires --replace-scm-with-registry for correct dependency resolution.
2. Set the flag in .vscode/settings.json:

   "swift.packageArguments": ["--replace-scm-with-registry"]

3. Resolve dependencies normally — Package.resolved is correct.
4. Wait for SourceKit-LSP background indexing to trigger a package resolution.
5. Observe that Package.resolved is overwritten with dependencies resolved without the --replace-scm-with-registry flag.

Logging

No response

[tracymiranda]

Related issue #1877

[dschaefer2]

Seems to also cause swiftlang/swift-package-manager#9924.