If you haven't already, could you please file a bug for this (bugs.swift.org)? This sounds like a compiler bug.
I tried to use the 5.3 Development branch but I got the same results. Project package dependencies are not being seen by sourcekit-lsp.
That's unexpected. Is this the same project as Importing modules from Vapor causing long delays - #3 by bmontegani ?
I will have to wait until your updates get into the 5.3 development branch.
Unfortunately, I suspect it is too late to take such a big and potentially destabilizing change in 5.3.
Also, It would be really nice if sourcekit-lsp fixes could also support earlier toolchains especially the currently released toolchain 5.2.4. Otherwise, we always have to wait for the next release to get any fixes/enhancements.
We've talked about creating a branch of sourcekit-lsp that is auto-merged from master sourcekit-lsp, but using the latest released toolchain swiftpm, covered by [SR-12491] Create a branch of sourcekit-lsp setup with the latest released Swift toolchain · Issue #536 · apple/sourcekit-lsp · GitHub I think this would be good to have, we just haven't had time to set up the infrastructure needed to keep a branch like this up to date.