Function text_encoding

crates/vm/src/stdlib/_io.rs:5228–5261

(
        encoding: PyObjectRef,
        stacklevel: OptionalArg<i32>,
        vm: &VirtualMachine,
    )

    #[pyfunction]
    fn text_encoding(
        encoding: PyObjectRef,
        stacklevel: OptionalArg<i32>,
        vm: &VirtualMachine,
    ) -> PyResult<PyStrRef> {
        if vm.is_none(&encoding) {
            let encoding = if vm.state.config.settings.utf8_mode > 0 {
                "utf-8"
            } else {
                "locale"
            };
            if vm.state.config.settings.warn_default_encoding {
                let mut stacklevel = stacklevel.unwrap_or(2);
                if stacklevel > 1
                    && let Some(frame) = vm.current_frame()
                    && let Some(stdlib_dir) = vm.state.config.paths.stdlib_dir.as_deref()
                {
                    let path = frame.code.source_path().as_str();
                    if !path.starts_with(stdlib_dir) {
                        stacklevel = stacklevel.saturating_sub(1);
                    }
                }
                let stacklevel = usize::try_from(stacklevel).unwrap_or(0);
                crate::stdlib::_warnings::warn(
                    vm.ctx.exceptions.encoding_warning,
                    "'encoding' argument not specified".to_owned(),
                    stacklevel,
                    vm,
                )?;
            }
            return Ok(vm.ctx.new_str(encoding));
        }
        encoding.try_into_value(vm)
    }

    #[cfg(test)]
    mod tests {