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|
use serde::de::value::{
MapAccessDeserializer, MapDeserializer, SeqDeserializer,
};
use std::borrow::Cow;
use dhall::syntax::NumKind;
use crate::value::SimpleValue;
use crate::{Error, ErrorKind, Result, Value};
pub trait Sealed {}
/// A data structure that can be deserialized from a Dhall expression.
///
/// This is automatically implemented for any type that [serde] can deserialize.
/// In fact, this trait cannot be implemented manually. To implement it for your type,
/// use serde's derive mechanism.
///
/// # Example
///
/// ```rust
/// # fn main() -> serde_dhall::Result<()> {
/// use serde::Deserialize;
///
/// // Use serde's derive
/// #[derive(Deserialize)]
/// struct Point {
/// x: u64,
/// y: u64,
/// }
///
/// // Convert a Dhall string to a Point.
/// let point: Point = serde_dhall::from_str("{ x = 1, y = 1 + 1 }").parse()?;
/// # Ok(())
/// # }
/// ```
///
/// [serde]: https://serde.rs
pub trait FromDhall: Sealed + Sized {
#[doc(hidden)]
fn from_dhall(v: &Value) -> Result<Self>;
}
impl<T> Sealed for T where T: serde::de::DeserializeOwned {}
struct Deserializer<'a>(Cow<'a, SimpleValue>);
impl<T> FromDhall for T
where
T: serde::de::DeserializeOwned,
{
fn from_dhall(v: &Value) -> Result<Self> {
let sval = v.to_simple_value().ok_or_else(|| {
Error(ErrorKind::Deserialize(format!(
"this cannot be deserialized into the serde data model: {}",
v
)))
})?;
T::deserialize(Deserializer(Cow::Owned(sval)))
}
}
impl<'de: 'a, 'a> serde::de::IntoDeserializer<'de, Error> for Deserializer<'a> {
type Deserializer = Deserializer<'a>;
fn into_deserializer(self) -> Self::Deserializer {
self
}
}
impl<'de: 'a, 'a> serde::Deserializer<'de> for Deserializer<'a> {
type Error = Error;
fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
where
V: serde::de::Visitor<'de>,
{
use std::convert::TryInto;
use NumKind::*;
use SimpleValue::*;
let val = |x| Deserializer(Cow::Borrowed(x));
match self.0.as_ref() {
Num(Bool(x)) => visitor.visit_bool(*x),
Num(Natural(x)) => {
if let Ok(x64) = (*x).try_into() {
visitor.visit_u64(x64)
} else if let Ok(x32) = (*x).try_into() {
visitor.visit_u32(x32)
} else {
unimplemented!()
}
}
Num(Integer(x)) => {
if let Ok(x64) = (*x).try_into() {
visitor.visit_i64(x64)
} else if let Ok(x32) = (*x).try_into() {
visitor.visit_i32(x32)
} else {
unimplemented!()
}
}
Num(Double(x)) => visitor.visit_f64((*x).into()),
Text(x) => visitor.visit_str(x),
List(xs) => {
visitor.visit_seq(SeqDeserializer::new(xs.iter().map(val)))
}
Optional(None) => visitor.visit_none(),
Optional(Some(x)) => visitor.visit_some(val(x)),
Record(m) => visitor.visit_map(MapDeserializer::new(
m.iter().map(|(k, v)| (k.as_ref(), val(v))),
)),
Union(field_name, Some(x)) => visitor.visit_enum(
MapAccessDeserializer::new(MapDeserializer::new(
Some((field_name.as_str(), val(x))).into_iter(),
)),
),
Union(field_name, None) => visitor.visit_enum(
MapAccessDeserializer::new(MapDeserializer::new(
Some((field_name.as_str(), ())).into_iter(),
)),
),
}
}
fn deserialize_tuple<V>(self, _: usize, visitor: V) -> Result<V::Value>
where
V: serde::de::Visitor<'de>,
{
let val = |x| Deserializer(Cow::Borrowed(x));
match self.0.as_ref() {
// Blindly takes keys in sorted order.
SimpleValue::Record(m) => visitor
.visit_seq(SeqDeserializer::new(m.iter().map(|(_, v)| val(v)))),
_ => self.deserialize_any(visitor),
}
}
serde::forward_to_deserialize_any! {
bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
bytes byte_buf option unit unit_struct newtype_struct seq
tuple_struct map struct enum identifier ignored_any
}
}
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