yarp_cli/rule_pack/
strict_json.rs

1use std::fmt;
2
3use serde::de::{DeserializeOwned, Error as _, MapAccess, SeqAccess, Visitor};
4use serde::{Deserialize, Deserializer};
5use serde_json::{Map, Number, Value};
6
7/// Decode strict JSON while rejecting duplicate and unknown fields.
8///
9/// # Errors
10///
11/// Returns an error when JSON syntax, duplicate keys, trailing data, or the target model is invalid.
12pub fn from_slice<T: DeserializeOwned>(bytes: &[u8]) -> Result<T, String> {
13    let mut deserializer = serde_json::Deserializer::from_slice(bytes);
14    let value = StrictValue::deserialize(&mut deserializer)
15        .map_err(|error| format!("invalid JSON: {error}"))?
16        .0;
17    deserializer
18        .end()
19        .map_err(|error| format!("invalid trailing JSON data: {error}"))?;
20    serde_json::from_value(value).map_err(|error| format!("invalid data: {error}"))
21}
22
23struct StrictValue(Value);
24
25impl<'de> Deserialize<'de> for StrictValue {
26    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
27    where
28        D: Deserializer<'de>,
29    {
30        deserializer.deserialize_any(StrictValueVisitor)
31    }
32}
33
34struct StrictValueVisitor;
35
36impl<'de> Visitor<'de> for StrictValueVisitor {
37    type Value = StrictValue;
38
39    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
40        formatter.write_str("a JSON value without duplicate object keys")
41    }
42
43    fn visit_bool<E>(self, value: bool) -> Result<Self::Value, E> {
44        Ok(StrictValue(Value::Bool(value)))
45    }
46
47    fn visit_i64<E>(self, value: i64) -> Result<Self::Value, E> {
48        Ok(StrictValue(Value::Number(Number::from(value))))
49    }
50
51    fn visit_u64<E>(self, value: u64) -> Result<Self::Value, E> {
52        Ok(StrictValue(Value::Number(Number::from(value))))
53    }
54
55    fn visit_f64<E>(self, value: f64) -> Result<Self::Value, E>
56    where
57        E: serde::de::Error,
58    {
59        Number::from_f64(value)
60            .map(Value::Number)
61            .map(StrictValue)
62            .ok_or_else(|| E::custom("non-finite JSON number"))
63    }
64
65    fn visit_str<E>(self, value: &str) -> Result<Self::Value, E> {
66        Ok(StrictValue(Value::String(value.to_owned())))
67    }
68
69    fn visit_string<E>(self, value: String) -> Result<Self::Value, E> {
70        Ok(StrictValue(Value::String(value)))
71    }
72
73    fn visit_none<E>(self) -> Result<Self::Value, E> {
74        Ok(StrictValue(Value::Null))
75    }
76
77    fn visit_unit<E>(self) -> Result<Self::Value, E> {
78        Ok(StrictValue(Value::Null))
79    }
80
81    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
82    where
83        D: Deserializer<'de>,
84    {
85        StrictValue::deserialize(deserializer)
86    }
87
88    fn visit_seq<A>(self, mut sequence: A) -> Result<Self::Value, A::Error>
89    where
90        A: SeqAccess<'de>,
91    {
92        let mut values = Vec::new();
93        while let Some(value) = sequence.next_element::<StrictValue>()? {
94            values.push(value.0);
95        }
96        Ok(StrictValue(Value::Array(values)))
97    }
98
99    fn visit_map<A>(self, mut object: A) -> Result<Self::Value, A::Error>
100    where
101        A: MapAccess<'de>,
102    {
103        let mut values = Map::new();
104        while let Some(key) = object.next_key::<String>()? {
105            if values.contains_key(&key) {
106                return Err(A::Error::custom(format!("duplicate object key: {key}")));
107            }
108            let value = object.next_value::<StrictValue>()?;
109            values.insert(key, value.0);
110        }
111        Ok(StrictValue(Value::Object(values)))
112    }
113}
114
115#[cfg(test)]
116mod tests {
117    use serde::Deserialize;
118
119    use super::*;
120
121    #[derive(Debug, Deserialize, Eq, PartialEq)]
122    #[serde(deny_unknown_fields)]
123    struct Example {
124        value: u32,
125    }
126
127    #[test]
128    fn rejects_duplicate_and_unknown_fields() {
129        assert!(from_slice::<Example>(br#"{"value":1,"value":2}"#).is_err());
130        assert!(from_slice::<Example>(br#"{"value":1,"other":2}"#).is_err());
131        assert_eq!(
132            from_slice::<Example>(br#"{"value":1}"#).expect("valid"),
133            Example { value: 1 }
134        );
135    }
136}
yarp_cli/rule_pack/strict_json.rs

yarp_cli/rule_pack/
strict_json.rs
