No diagnostics shown for Swift package in subfolder of workspace

[ahoppen]

When I have a directory structure like the following

abc
└── swifftest
    ├── Package.swift
    ├── Sources
    │   └── swifftest
    │       └── swifftest.swift
    └── Tests
        └── swifftestTests
            └── swifftestTests.swift

6 directories, 3 files

And I open the abc folder in VS Code, then navigate to swifttest.swift and introduce a syntax error in there, I don’t see any diagnostics. Looking at the SourceKit-LSP logs, it seems like no textDocument/diagnostics request is sent.