nushell/crates/nu-plugin/src/lib.rs

pub mod value_capnp {
    include!(concat!(env!("OUT_DIR"), "/value_capnp.rs"));
}

pub mod plugin_value {

    use crate::value_capnp::value;
    use capnp::serialize_packed;
    use nu_protocol::{Span, Value};

    pub fn serialize_value(value: &Value, writer: &mut impl std::io::Write) -> capnp::Result<()> {
        let mut message = ::capnp::message::Builder::new_default();

        {
            let mut serialized_value = message.init_root::<value::Builder>();

            let value_span = match value {
                Value::Nothing { span } => {
                    serialized_value.set_void(());
                    *span
                }
                Value::Bool { val, span } => {
                    serialized_value.set_bool(*val);
                    *span
                }
                Value::Int { val, span } => {
                    serialized_value.set_int(*val);
                    *span
                }
                Value::Float { val, span } => {
                    serialized_value.set_float(*val);
                    *span
                }
                Value::String { val, span } => {
                    serialized_value.set_string(&val);
                    *span
                }
                Value::List { vals, span } => {
                    {
                        serialize_list(vals, &mut serialized_value);
                    }
                    *span
                }
                _ => Span::unknown(),
            };

            {
                let mut span = serialized_value.reborrow().init_span();
                span.set_start(value_span.start as u64);
                span.set_end(value_span.end as u64);
            }
        }

        serialize_packed::write_message(writer, &message)
    }

    fn serialize_list(vals: &[Value], builder: &mut value::Builder) {
        let mut list_builder = builder.reborrow().init_list(vals.len() as u32);

        for (index, val) in vals.iter().enumerate() {
            match val {
                Value::Nothing { .. } => {
                    list_builder.reborrow().get(index as u32).set_void(());
                }
                Value::Bool { val, .. } => {
                    list_builder.reborrow().get(index as u32).set_bool(*val);
                }
                Value::Int { val, .. } => {
                    list_builder.reborrow().get(index as u32).set_int(*val);
                }
                Value::Float { val, .. } => {
                    list_builder.reborrow().get(index as u32).set_float(*val);
                }
                Value::String { val, .. } => {
                    list_builder.reborrow().get(index as u32).set_string(val);
                }
                Value::List { vals, .. } => serialize_list(vals, builder),
                _ => {}
            }
        }
    }

    pub fn deserialize_value(reader: &mut impl std::io::BufRead) -> Value {
        let message_reader =
            serialize_packed::read_message(reader, ::capnp::message::ReaderOptions::new()).unwrap();

        let plugin_value = message_reader.get_root::<value::Reader>().unwrap();

        let span_reader = plugin_value.get_span().unwrap();
        let span = Span {
            start: span_reader.get_start() as usize,
            end: span_reader.get_end() as usize,
        };

        match plugin_value.which() {
            Ok(value::Void(())) => Value::Nothing { span },
            Ok(value::Bool(val)) => Value::Bool { val, span },
            Ok(value::Int(val)) => Value::Int { val, span },
            Ok(value::Float(val)) => Value::Float { val, span },
            Ok(value::String(val)) => Value::String {
                val: val.unwrap().to_string(),
                span,
            },
            Ok(value::List(_)) => Value::Nothing {
                span: Span::unknown(),
            },
            Err(capnp::NotInSchema(_)) => Value::Nothing {
                span: Span::unknown(),
            },
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use nu_protocol::{Span, Value};

    #[test]
    fn value_round_trip() {
        let values = [
            Value::Bool {
                val: false,
                span: Span { start: 1, end: 20 },
            },
            Value::Int {
                val: 10,
                span: Span { start: 2, end: 30 },
            },
            Value::Float {
                val: 10.0,
                span: Span { start: 3, end: 40 },
            },
            Value::String {
                val: "a string".into(),
                span: Span { start: 4, end: 50 },
            },
        ];

        for value in values {
            let mut buffer: Vec<u8> = Vec::new();
            plugin_value::serialize_value(&value, &mut buffer).expect("unable to write message");
            let returned_value = plugin_value::deserialize_value(&mut buffer.as_slice());

            assert_eq!(value, returned_value)
        }

        {
            // Since nothing doesn't implement PartialOrd, we only compare that the
            // encoded and decoded spans are correct
            let value = Value::Nothing {
                span: Span { start: 0, end: 10 },
            };

            let mut buffer: Vec<u8> = Vec::new();
            plugin_value::serialize_value(&value, &mut buffer).expect("unable to write message");
            let returned_value = plugin_value::deserialize_value(&mut buffer.as_slice());

            assert_eq!(
                value.span().expect("span"),
                returned_value.span().expect("span")
            )
        }
    }
}