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//! Serde `Deserializer` module
use crate::{
de::{
escape::EscapedDeserializer, BorrowingReader, Deserializer, INNER_VALUE, UNFLATTEN_PREFIX,
},
errors::serialize::DeError,
events::{BytesStart, Event},
};
use serde::de::{self, DeserializeSeed, IntoDeserializer};
enum MapValue {
Empty,
/// Value should be deserialized from the attribute value
Attribute {
value: Vec<u8>,
},
Nested,
/// Value should be deserialized from the text content of the XML node:
///
/// ```xml
/// <...>text content for field value<...>
/// ```
InnerValue,
}
/// A deserializer for `Attributes`
pub(crate) struct MapAccess<'de, 'a, R: BorrowingReader<'de> + 'a> {
/// Tag -- owner of attributes
start: BytesStart<'de>,
de: &'a mut Deserializer<'de, R>,
/// Position in flat byte slice of all attributes from which next
/// attribute should be parsed. This field is required because we
/// do not store reference to `Attributes` itself but instead create
/// a new object on each advance of `Attributes` iterator, so we need
/// to restore last position before advance.
position: usize,
value: MapValue,
}
impl<'de, 'a, R: BorrowingReader<'de>> MapAccess<'de, 'a, R> {
/// Create a new MapAccess
pub fn new(de: &'a mut Deserializer<'de, R>, start: BytesStart<'de>) -> Result<Self, DeError> {
let position = start.attributes().position;
Ok(MapAccess {
de,
start,
position,
value: MapValue::Empty,
})
}
fn next_attr(&mut self) -> Result<Option<(Vec<u8>, Vec<u8>)>, DeError> {
let mut attributes = self.start.attributes();
attributes.position = self.position;
let next_att = attributes.next().transpose()?;
self.position = attributes.position;
Ok(next_att.map(|a| (a.key.to_owned(), a.value.into_owned())))
}
}
impl<'de, 'a, R: BorrowingReader<'de> + 'a> de::MapAccess<'de> for MapAccess<'de, 'a, R> {
type Error = DeError;
fn next_key_seed<K: DeserializeSeed<'de>>(
&mut self,
seed: K,
) -> Result<Option<K::Value>, Self::Error> {
let decoder = self.de.reader.decoder();
let has_value_field = self.de.has_value_field;
let has_unflatten_field = self.de.has_unflatten_field;
if let Some((key, value)) = self.next_attr()? {
// try getting map from attributes (key= "value")
self.value = MapValue::Attribute { value };
seed.deserialize(EscapedDeserializer::new(key, decoder, false))
.map(Some)
} else {
// try getting from events (<key>value</key>)
match self.de.peek()? {
Some(Event::Text(_)) => {
self.value = MapValue::InnerValue;
// Deserialize `key` from special attribute name which means
// that value should be taken from the text content of the
// XML node
seed.deserialize(INNER_VALUE.into_deserializer()).map(Some)
}
// Used to deserialize collections of enums, like:
// <root>
// <A/>
// <B/>
// <C/>
// </root>
//
// into
//
// enum Enum { A, B, ะก }
// struct Root {
// #[serde(rename = "$value")]
// items: Vec<Enum>,
// }
// TODO: This should be handled by #[serde(flatten)]
// See https://github.com/serde-rs/serde/issues/1905
Some(Event::Start(_)) if has_value_field => {
self.value = MapValue::InnerValue;
seed.deserialize(INNER_VALUE.into_deserializer()).map(Some)
}
Some(Event::Start(e)) if has_unflatten_field => {
self.value = MapValue::InnerValue;
let key = format!(
"{}{}",
UNFLATTEN_PREFIX,
String::from_utf8(e.local_name().to_vec())
.expect("$unflatten= did not contain valid Rust identifier")
);
seed.deserialize(key.into_deserializer()).map(Some)
}
Some(Event::Start(e)) => {
let name = e.local_name().to_owned();
self.value = MapValue::Nested;
seed.deserialize(EscapedDeserializer::new(name, decoder, false))
.map(Some)
}
_ => Ok(None),
}
}
}
fn next_value_seed<K: DeserializeSeed<'de>>(
&mut self,
seed: K,
) -> Result<K::Value, Self::Error> {
match std::mem::replace(&mut self.value, MapValue::Empty) {
MapValue::Attribute { value } => seed.deserialize(EscapedDeserializer::new(
value,
self.de.reader.decoder(),
true,
)),
MapValue::Nested | MapValue::InnerValue => seed.deserialize(&mut *self.de),
MapValue::Empty => Err(DeError::EndOfAttributes),
}
}
}