Implement PyClass for PathBuf and Path

[kangalio]

There exists an infallible conversion from String to PathBuf (and hence Path), so if I'm not missing something, there is no real reason not to implement PyClass for PathBuf/Path.

That would allow Rust functions exposed to Python to take paths as parameters with the actual appropriate Rust type, instead of having to use String as a workaround.

[kangalio]

I'm trying to make a PR for this

[davidhewitt]

I think rather than PyClass, you should implement IntoPy<PyObject>, ToPyObject, and FromPyObject for PathBuf (and maybe Path, if you can make it work).

[kangalio]

I think it will be better to implement those three traits on OsStr and OsString, because that's what the this work is really about: converting between Python's magic strings and Rust's opaque OS strings.

Path and PathBuf can just redirect to the implementations on OsStr and OsString.

[davidhewitt]

That sounds sensible to me! If you're looking at string types, it could be worth assessing if CStr and CString should also be supported. I think Python allows null bytes in the middle of its strings so definitely from-Python would be fallible for those.

[kangalio]

Should the conversion functions from/to OsStr/Cstr go onto the PyString struct? It would get four new methods:

• from_osstr
• to_osstr
• from_cstr
• to_cstr

The alternative would be to create new modules types/cstr.rs and types/osstr.rs, and implement the conversions there

[davidhewitt]

I would suggest avoiding new methods on PyString if we can - as much as possible the methods on the python-native types are just wrappers around the underlying Python C API.

Is there a reason the traits above don't provide enough functionality for what you need? The traits are all we need for #[pyfunction] / #[pymethods] etc.

[kangalio]

I was just asking what you preferred, I'm fine with both.

In any case, I wrote the trait implementations for OsStr/OsString: https://github.com/kangalioo/pyo3/blob/bbc578fda767134ff678c1ebc62eae5e0e756cb2/src/types/osstr.rs. I'd greatly appreciate if you could check it out to make sure I didn't do anything totally stupid. Comments with // HELP mark places where I was unsure if I was doing the right thing.

In the meantime, I'll be working on CStr/CString and Path/PathBuf.

EDIT: Actually, I'm not gonna do the conversions for CStr/CString in this PR, since they're not really strings but byte arrays, so they don't fit with the rest of the PR. (And also because I don't see a big need to transfer C strings between Rust and Python and the work to support it doesn't seem to be worth it for me right now)

[davidhewitt]

👍 totally makes sense - nice work and thanks for the PR; I'll do my best to make time to review it as soon as I can.

[davidhewitt]

Closed by #1379 . Thanks again for the PR.