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//! Serde `Deserializer` module
use crate::{
de::escape::EscapedDeserializer,
de::{DeEvent, Deserializer, XmlRead, INNER_VALUE, UNFLATTEN_PREFIX},
errors::serialize::DeError,
events::attributes::IterState,
events::BytesStart,
};
use serde::de::{self, DeserializeSeed, IntoDeserializer};
use std::borrow::Cow;
use std::ops::Range;
/// Representing state of the `MapAccess` accessor.
enum State {
/// `next_key_seed` not yet called. This is initial state and state after deserializing
/// value (calling `next_value_seed`).
Empty,
/// `next_key_seed` checked the attributes list and find it is not exhausted yet.
/// Next call to the `next_value_seed` will deserialize type from the attribute value
Attribute(Range<usize>),
/// The same as `InnerValue`
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>
where
R: XmlRead<'de>,
{
/// Tag -- owner of attributes
start: BytesStart<'de>,
de: &'a mut Deserializer<'de, R>,
/// State of the iterator over attributes. Contains the next position in the
/// inner `start` slice, from which next attribute should be parsed.
iter: IterState,
/// Current state of the accessor that determines what next call to API
/// methods should return.
state: State,
/// list of fields yet to unflatten (defined as starting with $unflatten=)
unflatten_fields: Vec<&'static [u8]>,
}
impl<'de, 'a, R> MapAccess<'de, 'a, R>
where
R: XmlRead<'de>,
{
/// Create a new MapAccess
pub fn new(
de: &'a mut Deserializer<'de, R>,
start: BytesStart<'de>,
fields: &[&'static str],
) -> Result<Self, DeError> {
Ok(MapAccess {
de,
start,
iter: IterState::new(0, false),
state: State::Empty,
unflatten_fields: fields
.iter()
.filter(|f| f.starts_with(UNFLATTEN_PREFIX))
.map(|f| f.as_bytes())
.collect(),
})
}
}
impl<'de, 'a, R> de::MapAccess<'de> for MapAccess<'de, 'a, R>
where
R: XmlRead<'de>,
{
type Error = DeError;
fn next_key_seed<K: DeserializeSeed<'de>>(
&mut self,
seed: K,
) -> Result<Option<K::Value>, Self::Error> {
// FIXME: There error positions counted from end of tag name - need global position
let slice = self.start.attributes_raw();
let decoder = self.de.reader.decoder();
let has_value_field = self.de.has_value_field;
if let Some(a) = self.iter.next(slice).transpose()? {
// try getting map from attributes (key= "value")
let (key, value) = a.into();
self.state = State::Attribute(value.unwrap_or_default());
seed.deserialize(EscapedDeserializer::new(
Cow::Borrowed(&slice[key]),
decoder,
false,
))
.map(Some)
} else {
// try getting from events (<key>value</key>)
match self.de.peek()? {
DeEvent::Text(_) | DeEvent::CData(_) => {
self.state = State::InnerValue;
// Deserialize `key` from special attribute name which means
// that value should be taken from the text content of the
// XML node
seed.deserialize(INNER_VALUE.into_deserializer()).map(Some)
}
// Used to deserialize collections of enums, like:
// <root>
// <A/>
// <B/>
// <C/>
// </root>
//
// into
//
// enum Enum { A, B, ะก }
// struct Root {
// #[serde(rename = "$value")]
// items: Vec<Enum>,
// }
// TODO: This should be handled by #[serde(flatten)]
// See https://github.com/serde-rs/serde/issues/1905
DeEvent::Start(_) if has_value_field => {
self.state = State::InnerValue;
seed.deserialize(INNER_VALUE.into_deserializer()).map(Some)
}
DeEvent::Start(e) => {
let key = if let Some(p) = self
.unflatten_fields
.iter()
.position(|f| e.name() == &f[UNFLATTEN_PREFIX.len()..])
{
// Used to deserialize elements, like:
// <root>
// <xxx>test</xxx>
// </root>
//
// into
//
// struct Root {
// #[serde(rename = "$unflatten=xxx")]
// xxx: String,
// }
self.state = State::InnerValue;
seed.deserialize(self.unflatten_fields.remove(p).into_deserializer())
} else {
let name = Cow::Borrowed(e.local_name());
self.state = State::Nested;
seed.deserialize(EscapedDeserializer::new(name, decoder, false))
};
key.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.state, State::Empty) {
State::Attribute(value) => {
let slice = self.start.attributes_raw();
let decoder = self.de.reader.decoder();
seed.deserialize(EscapedDeserializer::new(
Cow::Borrowed(&slice[value]),
decoder,
true,
))
}
State::Nested | State::InnerValue => seed.deserialize(&mut *self.de),
State::Empty => Err(DeError::EndOfAttributes),
}
}
}