No std::string -> nanobind::str conversion?

[nschloe]

When trying to pass a std::string to an nb function that accepts an nb::str, compilation will fail:

note:   no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} to ‘const nanobind::str&’

Converting it to a char* via std::string::c_str() also won't work:

note:   no known conversion for argument 1 from ‘const char*’ to ‘const nanobind::str&’

String literals work.

Any hints?

[wjakob]

nb::str has an explicit conversion from char * (but not an implicit one!). You must cast it like so: nb::str(std_str.c_str()). There is no way that there could be a nb::str constructor that takes std::string — nanobind tries as hard as possible to not include any unnecessary STL headers.

What I would suggest is that you make your own nb::str subclass (nschloe_str ;)) with all the implicit and explicit constructors you fancy. Since it derives from a builtin wrapper type, nanobind knows how to accept and return it in bindings.

[nschloe]

Perhaps that's an item for the Porting guide.

[wjakob]

Would you be willing to make a PR for such a note?

[nschloe]

I can draft something. Perhaps this should be answered together with #310 under "Strings in Nb".