Using Maturin with a local python dependency.

[Ruhrpottpatriot]

I have an existing Python project where we have to rewrite performance critical features in Rust. The project has local python dependencies which reside in adjacent folders to the project, i.e. like this:

workspace/
├── project/ 
│   ├── Cargo.toml
│   ├── rust/src/lib.rs
│   ├── src/project/foo.py
│   ├── pyproject.toml  
│   └── ...
└── dep/ 
    ├── pyproject.toml
    └── src/dep/

For various reasons I can't simply use a git:// dependency and for other reasons the package is also not in a python package registry. This constraints are highly unlikely to change.

I'm currently using hatch and hatchling to manage the projects virtual environments for development, unit-testing, etc. With hatch I can do this:

dependencies = [
   ...
  "dep @ {root:parent:uri}/dep/",
]

However, this doesn't work with maturin, or at least I haven't gotten it to work. If I do maturin develop from inside a hatch venv I get:

💥 maturin failed
Caused by: pyproject.toml at G:\project\pyproject.toml is invalid
Caused by: TOML parse error at line 14, column 16
|
14 | dependencies = ["dep @ {root:parent:uri}/dep"]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Not a URL (missing scheme): {root:parent:uri}/dep
dep @ {root:parent:uri}/dep

What's the proper way to solve this problem?