Method find_coder

crates/vm/src/stdlib/_io.rs:2919–3001

(
            buffer: &PyObject,
            encoding: &str,
            errors: &Py<PyUtf8Str>,
            newline: Newlines,
            vm: &VirtualMachine,
        )

        #[allow(clippy::type_complexity)]
        fn find_coder(
            buffer: &PyObject,
            encoding: &str,
            errors: &Py<PyUtf8Str>,
            newline: Newlines,
            vm: &VirtualMachine,
        ) -> PyResult<(
            Option<(PyObjectRef, Option<EncodeFunc>)>,
            Option<PyObjectRef>,
        )> {
            let codec = vm.state.codec_registry.lookup(encoding, vm)?;
            if !codec.is_text_codec(vm)? {
                return Err(vm.new_lookup_error(format!(
                    "'{encoding}' is not a text encoding; use codecs.open() to handle arbitrary codecs"
                )));
            }
            let errors = errors.to_owned().into_wtf8();

            let encoder = if vm.call_method(buffer, "writable", ())?.try_to_bool(vm)? {
                let incremental_encoder =
                    match codec.get_incremental_encoder(Some(errors.clone()), vm) {
                        Ok(encoder) => encoder,
                        Err(err)
                            if err.fast_isinstance(vm.ctx.exceptions.type_error)
                                || err.fast_isinstance(vm.ctx.exceptions.attribute_error) =>
                        {
                            let name = vm
                                .get_attribute_opt(codec.as_tuple().to_owned().into(), "name")?
                                .and_then(|obj| obj.downcast::<PyStr>().ok());
                            StatelessIncrementalEncoder {
                                encode: codec.get_encode_func().to_owned(),
                                errors: Some(errors.clone()),
                                name,
                            }
                            .into_ref(&vm.ctx)
                            .into()
                        }
                        Err(err) => return Err(err),
                    };
                let encoding_name = vm.get_attribute_opt(incremental_encoder.clone(), "name")?;
                let encode_func = encoding_name.and_then(|name| {
                    let name = name.downcast_ref::<PyStr>()?;
                    match name.to_str()? {
                        "utf-8" => Some(textio_encode_utf8 as EncodeFunc),
                        _ => None,
                    }
                });
                Some((incremental_encoder, encode_func))
            } else {
                None
            };

            let decoder = if vm.call_method(buffer, "readable", ())?.try_to_bool(vm)? {
                let decoder = match codec.get_incremental_decoder(Some(errors.clone()), vm) {
                    Ok(decoder) => decoder,
                    Err(err)
                        if err.fast_isinstance(vm.ctx.exceptions.type_error)
                            || err.fast_isinstance(vm.ctx.exceptions.attribute_error) =>