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json.rs
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use std::fmt;
use serde;
use serde::de::{DeserializeSeed, Visitor};
use serde::ser::{SerializeMap, SerializeSeq};
use serde_json;
use crate::obj::{
objbool, objdict, objfloat, objint, objsequence,
objstr::{self, PyString},
objtype,
};
use crate::pyobject::{
create_type, DictProtocol, IdProtocol, PyContext, PyFuncArgs, PyObjectRef, PyResult,
TypeProtocol,
};
use crate::VirtualMachine;
use num_traits::cast::ToPrimitive;
// We need to have a VM available to serialise a PyObject based on its subclass, so we implement
// PyObject serialisation via a proxy object which holds a reference to a VM
struct PyObjectSerializer<'s> {
pyobject: &'s PyObjectRef,
vm: &'s VirtualMachine,
}
impl<'s> PyObjectSerializer<'s> {
fn clone_with_object(&self, pyobject: &'s PyObjectRef) -> PyObjectSerializer {
PyObjectSerializer {
pyobject,
vm: self.vm,
}
}
}
impl<'s> serde::Serialize for PyObjectSerializer<'s> {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: serde::Serializer,
{
let serialize_seq_elements =
|serializer: S, elements: &Vec<PyObjectRef>| -> Result<S::Ok, S::Error> {
let mut seq = serializer.serialize_seq(Some(elements.len()))?;
for e in elements.iter() {
seq.serialize_element(&self.clone_with_object(e))?;
}
seq.end()
};
if objtype::isinstance(self.pyobject, &self.vm.ctx.str_type()) {
serializer.serialize_str(&objstr::get_value(&self.pyobject))
} else if objtype::isinstance(self.pyobject, &self.vm.ctx.float_type()) {
serializer.serialize_f64(objfloat::get_value(self.pyobject))
} else if objtype::isinstance(self.pyobject, &self.vm.ctx.bool_type()) {
serializer.serialize_bool(objbool::get_value(self.pyobject))
} else if objtype::isinstance(self.pyobject, &self.vm.ctx.int_type()) {
let v = objint::get_value(self.pyobject);
serializer.serialize_i64(v.to_i64().unwrap())
// Although this may seem nice, it does not give the right result:
// v.serialize(serializer)
} else if objtype::isinstance(self.pyobject, &self.vm.ctx.list_type())
|| objtype::isinstance(self.pyobject, &self.vm.ctx.tuple_type())
{
let elements = objsequence::get_elements(self.pyobject);
serialize_seq_elements(serializer, &elements)
} else if objtype::isinstance(self.pyobject, &self.vm.ctx.dict_type()) {
let pairs = objdict::get_elements(self.pyobject);
let mut map = serializer.serialize_map(Some(pairs.len()))?;
for (key, e) in pairs.iter() {
map.serialize_entry(&key, &self.clone_with_object(&e.1))?;
}
map.end()
} else if self.pyobject.is(&self.vm.get_none()) {
serializer.serialize_none()
} else {
Err(serde::ser::Error::custom(format!(
"Object of type '{:?}' is not serializable",
self.pyobject.typ()
)))
}
}
}
// This object is used as the seed for deserialization so we have access to the PyContext for type
// creation
#[derive(Clone)]
struct PyObjectDeserializer<'c> {
vm: &'c VirtualMachine,
}
impl<'de> serde::de::DeserializeSeed<'de> for PyObjectDeserializer<'de> {
type Value = PyObjectRef;
fn deserialize<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
where
D: serde::Deserializer<'de>,
{
deserializer.deserialize_any(self.clone())
}
}
impl<'de> Visitor<'de> for PyObjectDeserializer<'de> {
type Value = PyObjectRef;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("a type that can deserialise in Python")
}
fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
Ok(self.vm.ctx.new_str(value.to_string()))
}
fn visit_string<E>(self, value: String) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
Ok(self.vm.ctx.new_str(value))
}
fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
// The JSON deserializer always uses the i64/u64 deserializers, so we only need to
// implement those for now
Ok(self.vm.ctx.new_int(value))
}
fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
// The JSON deserializer always uses the i64/u64 deserializers, so we only need to
// implement those for now
Ok(self.vm.ctx.new_int(value))
}
fn visit_f64<E>(self, value: f64) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
Ok(self.vm.ctx.new_float(value))
}
fn visit_bool<E>(self, value: bool) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
Ok(self.vm.ctx.new_bool(value))
}
fn visit_seq<A>(self, mut access: A) -> Result<Self::Value, A::Error>
where
A: serde::de::SeqAccess<'de>,
{
let mut seq = Vec::with_capacity(access.size_hint().unwrap_or(0));
while let Some(value) = access.next_element_seed(self.clone())? {
seq.push(value);
}
Ok(self.vm.ctx.new_list(seq))
}
fn visit_map<M>(self, mut access: M) -> Result<Self::Value, M::Error>
where
M: serde::de::MapAccess<'de>,
{
let dict = self.vm.ctx.new_dict();
// TODO: Given keys must be strings, we can probably do something more efficient
// than wrapping the given object up and then unwrapping it to determine whether or
// not it is a string
while let Some((key_obj, value)) = access.next_entry_seed(self.clone(), self.clone())? {
let key: String = match key_obj.payload::<PyString>() {
Some(PyString { ref value }) => value.clone(),
_ => unimplemented!("map keys must be strings"),
};
dict.set_item(&self.vm.ctx, &key, value);
}
Ok(dict)
}
fn visit_unit<E>(self) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
Ok(self.vm.ctx.none.clone())
}
}
/// Implement json.dumps
fn json_dumps(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
// TODO: Implement non-trivial serialisation case
arg_check!(vm, args, required = [(obj, None)]);
let res = {
let serializer = PyObjectSerializer { pyobject: obj, vm };
serde_json::to_string(&serializer)
};
let string = res.map_err(|err| vm.new_type_error(format!("{}", err)))?;
Ok(vm.context().new_str(string))
}
/// Implement json.loads
fn json_loads(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
// TODO: Implement non-trivial deserialization case
arg_check!(vm, args, required = [(string, Some(vm.ctx.str_type()))]);
let res = {
let de = PyObjectDeserializer { vm };
// TODO: Support deserializing string sub-classes
de.deserialize(&mut serde_json::Deserializer::from_str(&objstr::get_value(
&string,
)))
};
res.map_err(|err| {
let json_decode_error = vm
.sys_module
.get_item("modules")
.unwrap()
.get_item("json")
.unwrap()
.get_item("JSONDecodeError")
.unwrap();
let exc = vm.new_exception(json_decode_error, format!("{}", err));
vm.ctx.set_attr(&exc, "lineno", vm.ctx.new_int(err.line()));
vm.ctx.set_attr(&exc, "colno", vm.ctx.new_int(err.column()));
exc
})
}
pub fn mk_module(ctx: &PyContext) -> PyObjectRef {
// TODO: Make this a proper type with a constructor
let json_decode_error = create_type(
"JSONDecodeError",
&ctx.type_type,
&ctx.exceptions.exception_type,
&ctx.dict_type,
);
py_module!(ctx, "json", {
"dumps" => ctx.new_rustfunc(json_dumps),
"loads" => ctx.new_rustfunc(json_loads),
"JSONDecodeError" => json_decode_error
})
}