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support seeded deserialize for stream #1270

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65 changes: 54 additions & 11 deletions src/de.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2268,7 +2268,6 @@ pub struct StreamDeserializer<'de, R, T> {
impl<'de, R, T> StreamDeserializer<'de, R, T>
where
R: read::Read<'de>,
T: de::Deserialize<'de>,
{
/// Create a JSON stream deserializer from one of the possible serde_json
/// input sources.
Expand Down Expand Up @@ -2338,16 +2337,48 @@ where
}
}
}
}

impl<'de, R, T> Iterator for StreamDeserializer<'de, R, T>
where
R: Read<'de>,
T: de::Deserialize<'de>,
{
type Item = Result<T>;

fn next(&mut self) -> Option<Result<T>> {
/// Deserialize the next JSON value using the provided seed.
///
/// ```
/// use serde_json::{Deserializer, Value};
///
/// /// A simple `DeserializeSeed` impl that deserializes into a vec,
/// /// rather than returning the deserialized value.
/// struct Collect<'a, T: 'a>(&'a mut Vec<T>);
///
/// impl<'de, 'a, T> serde::de::DeserializeSeed<'de> for Collect<'a, T>
/// where
/// T: serde::de::Deserialize<'de>,
/// {
/// type Value = ();
///
/// fn deserialize<D>(self, deserializer: D) -> Result<(), D::Error>
/// where
/// D: serde::de::Deserializer<'de>,
/// {
/// self.0.push(T::deserialize(deserializer)?);
/// Ok(())
/// }
/// }
///
/// fn main() {
/// let data = "{\"k\": 3}1\"cool\"\"stuff\" 3{} [0, 1, 2]";
///
/// let mut stream = Deserializer::from_str(data).into_iter();
///
/// let mut values: Vec<Value> = vec![];
/// while let Some(res) = stream.next_seed(Collect(&mut values)) {
/// res.unwrap();
/// }
///
/// println!("{values:?}")
/// }
/// ```
pub fn next_seed<S>(&mut self, seed: S) -> Option<Result<T>>
where
S: de::DeserializeSeed<'de, Value = T>,
{
if R::should_early_return_if_failed && self.failed {
return None;
}
Expand All @@ -2369,7 +2400,7 @@ where
_ => false,
};
self.offset = self.de.read.byte_offset();
let result = de::Deserialize::deserialize(&mut self.de);
let result = seed.deserialize(&mut self.de);

Some(match result {
Ok(value) => {
Expand All @@ -2394,6 +2425,18 @@ where
}
}

impl<'de, R, T> Iterator for StreamDeserializer<'de, R, T>
where
R: Read<'de>,
T: de::Deserialize<'de>,
{
type Item = Result<T>;

fn next(&mut self) -> Option<Self::Item> {
self.next_seed(self.output)
}
}

impl<'de, R, T> FusedIterator for StreamDeserializer<'de, R, T>
where
R: Read<'de> + Fused,
Expand Down
53 changes: 53 additions & 0 deletions tests/stream.rs
Original file line number Diff line number Diff line change
Expand Up @@ -150,6 +150,59 @@ fn test_json_stream_primitive() {
});
}

#[test]
fn test_json_stream_seed() {
struct Seed;
impl<'de> serde::de::DeserializeSeed<'de> for Seed {
type Value = Value;
fn deserialize<D>(self, deserializer: D) -> Result<Value, D::Error>
where
D: serde::Deserializer<'de>,
{
let value: Value = serde::Deserialize::deserialize(deserializer)?;

// apply some modifications to test that the seed is working
Ok(match value {
Value::Bool(b) => Value::Bool(!b),
Value::Number(n) => Value::String(n.to_string()),
Value::String(s) => Value::String(s.to_uppercase()),
v => v,
})
}
}

let data = "{} true{}1[]\nfalse\"hey\"2 ";

test_stream!(data, Value, |stream| {
assert_eq!(stream.next_seed(Seed).unwrap().unwrap(), json!({}));
assert_eq!(stream.byte_offset(), 2);

assert_eq!(stream.next_seed(Seed).unwrap().unwrap(), false);
assert_eq!(stream.byte_offset(), 7);

assert_eq!(stream.next_seed(Seed).unwrap().unwrap(), json!({}));
assert_eq!(stream.byte_offset(), 9);

assert_eq!(stream.next_seed(Seed).unwrap().unwrap(), "1");
assert_eq!(stream.byte_offset(), 10);

assert_eq!(stream.next_seed(Seed).unwrap().unwrap(), json!([]));
assert_eq!(stream.byte_offset(), 12);

assert_eq!(stream.next_seed(Seed).unwrap().unwrap(), true);
assert_eq!(stream.byte_offset(), 18);

assert_eq!(stream.next_seed(Seed).unwrap().unwrap(), "HEY");
assert_eq!(stream.byte_offset(), 23);

assert_eq!(stream.next_seed(Seed).unwrap().unwrap(), "2");
assert_eq!(stream.byte_offset(), 24);

assert!(stream.next_seed(Seed).is_none());
assert_eq!(stream.byte_offset(), 25);
});
}

#[test]
fn test_json_stream_invalid_literal() {
let data = "truefalse";
Expand Down