Change builtin type caster: const char* to bytes

[legendre6891]

In this setup, the function f uses the type caster str to const char*.

int f(const char* buf) {
    // (do something) and return an integer
}

NB_MODULE(..., m) {
   m.def("f", &f);
}

This means that it is not possible to call f with a bytes object:

>>> f(b'123')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: f(): incompatible function arguments. The following argument types are supported:
    1. f(arg: str, /) -> int

Invoked with types: bytes

The association from const char* seems to be hardcoded in nb_cast.h. I'm curious if there is a way to override this? Namely, the binding function takes bytes as input instead of str?

[legendre6891]

It seems like I could use this to achieve my goal:

-int f(const char* buf) {
+int f(nb::bytes buf) {

This seems to rely on wrappers instead of type-casters. I'm curious if this is the recommended solution? (Is there a way to do this which just uses type casters?)

[wjakob]

Nanobind will not let you pass a Python bytes to a function expecting const char * (which is interpreted as character data, typically UTF8). This is by design. Declaring a wrapper that takes nb::bytes as you suggested sounds like a good solution.