Add path option for Python source

[messense]

With this PR you can specify Python source code location in Cargo.toml by setting package.metadata.maturin.python-source to your Python source code directory.

Here is an example project layout with python-source set to python:

├── Cargo.lock
├── Cargo.toml
├── Readme.md
├── check_installed
│   └── check_installed.py
├── python
│   ├── pyo3_mixed_py_subdir
│   │   ├── __init__.py
│   │   └── python_module
│   │       ├── __init__.py
│   │       └── double.py
│   └── pyproject.toml
├── src
│   └── lib.rs
├── test_pyo3_mixed.py
└── tox.ini

Closes #335

[messense]

FIXME: pyproject.toml should be relative to Python source instead of Cargo.toml. It's wrong, see 41a49b6

[messense]

cc @sebpuetz @davidhewitt @ijl

[davidhewitt]

👍 This seems like a good idea, it's nice to give users this flexibility!

[davidhewitt]

(This looks good to me, apart from missing README. I would approve, but historically I haven't been an approver / reviewer for maturin. If you want more review capacity I'm happy to start reviewing & approving maturin PRs?)

[messense]

If you want more review capacity I'm happy to start reviewing & approving maturin PRs?

That would be great. konstin emailed me that he won't be actively maintain maturin nowaday.

[ShanWeera]

@messense I'm on Windows 10, Python 3.8 and using Maturin 0.11.3-beta.2.

I can't seem to get python-source working on my end. The folder structure is similar to what's documented in the README. The Python source files are not copied over. Works fine with lib.name.

Any ideas?

[davidhewitt]

@ShanWeera Can you share the cargo.toml which doesn't work?

[messense]

@ShanWeera Please open a new issue so we can track it.