Cross-referencing between packages

This is my first post here on the Theia board so first of all I would like to say Hi to everyone and thanks for welcoming me in the community.

My question is about referencing foreign types inside a monorepo:
I followed the same pattern as in the Theia-IDE git repo, i.e., the extensions are located within a packages folder to be found by lerna.
There are two extensions within that folder.
On the top-layer tsconfig.json, I set the baseUrl to “.” and added path mappings from the src to the lib folder of each extension. In lerna.json, the useWorkspaces property is set to true and packages/* is registered as workspace in top-level package.json.
However, when I reference one extension’s type inside another extension, lerna complains that the file containing the type would not be in the project file list.

When I add a “references” entry to the referencing extension’s tsconfig.json that points to the referenced extension folder, it works fine. But shouldn’t it be possible without that entry using lerna? In the Theia-IDE git, I did not see such references but it transpiles without such issues.
Maybe I missed something. Thanks a lot for your suggestions!

Edit: My fault. In one file I accidentally included a source file of the other extension explicitly using a src-path instead of a lib path. Thus, the path rule did not apply. Now it works without the reference entry.

[original thread by Florian Göbe]