Avoid locking projects without source

[T-256]

1. rye init test && cd test
2. remove src folder

The suggestion is rye lock should not contain -e file:. line.

[bluss]

don't you want an explicit marker (like workspace-only) for this? You can have a python library without a src directory, have the files somewhere else.

[T-256]

don't you want an explicit marker (like workspace-only) for this?

it's differed from workspace-only. Currently with above steps, the build backend (e.g. hatchling) builds the project successfully, but actually it's empty package (not importable) and only package-info folder exists in site-packages.

You can have a python library without a src directory, have the files somewhere else.

Here I don't mean only src folder, it's just example for known build backends that contain source code in src/{project} folder. also, the main work here is to detect empty packages before (or after?) building them.