serde_with/
json.rs

1//! De/Serialization of JSON
2//!
3//! This modules is only available when using the `json` feature of the crate.
4
5use crate::prelude::*;
6
7/// Serialize value as string containing JSON
8///
9/// *Note*: This type is not necessary for normal usage of serde with JSON.
10/// It is only required if the serialized format contains a string, which itself contains JSON.
11///
12/// # Errors
13///
14/// Serialization can fail if `T`'s implementation of `Serialize` decides to
15/// fail, or if `T` contains a map with non-string keys.
16///
17/// # Examples
18///
19/// ```
20/// # #[cfg(feature = "macros")] {
21/// # use serde::{Deserialize, Serialize};
22/// # use serde_with::{serde_as, json::JsonString};
23/// #
24/// #[serde_as]
25/// #[derive(Deserialize, Serialize)]
26/// struct A {
27///     #[serde_as(as = "JsonString")]
28///     other_struct: B,
29/// }
30/// #[derive(Deserialize, Serialize)]
31/// struct B {
32///     value: usize,
33/// }
34///
35/// let v: A = serde_json::from_str(r#"{"other_struct":"{\"value\":5}"}"#).unwrap();
36/// assert_eq!(5, v.other_struct.value);
37///
38/// let x = A {
39///     other_struct: B { value: 10 },
40/// };
41/// assert_eq!(
42///     r#"{"other_struct":"{\"value\":10}"}"#,
43///     serde_json::to_string(&x).unwrap()
44/// );
45/// # }
46/// ```
47///
48/// The `JsonString` converter takes a type argument, which allows altering the serialization behavior of the inner value, before it gets turned into a JSON string.
49///
50/// ```
51/// # #[cfg(feature = "macros")] {
52/// # use serde::{Deserialize, Serialize};
53/// # use serde_with::{serde_as, json::JsonString};
54/// # use std::collections::BTreeMap;
55/// #
56/// #[serde_as]
57/// #[derive(Debug, Serialize, Deserialize, PartialEq)]
58/// struct Struct {
59///     #[serde_as(as = "JsonString<Vec<(JsonString, _)>>")]
60///     value: BTreeMap<[u8; 2], u32>,
61/// }
62///
63/// let value = Struct {
64///     value: BTreeMap::from([([1, 2], 3), ([4, 5], 6)]),
65/// };
66/// assert_eq!(
67///     r#"{"value":"[[\"[1,2]\",3],[\"[4,5]\",6]]"}"#,
68///     serde_json::to_string(&value).unwrap()
69/// );
70/// # }
71/// ```
72pub struct JsonString<T = Same>(PhantomData<T>);
73
74impl<T, TAs> SerializeAs<T> for JsonString<TAs>
75where
76    TAs: SerializeAs<T>,
77{
78    fn serialize_as<S>(source: &T, serializer: S) -> Result<S::Ok, S::Error>
79    where
80        S: Serializer,
81    {
82        serializer.serialize_str(
83            &serde_json::to_string(&SerializeAsWrap::<T, TAs>::new(source))
84                .map_err(SerError::custom)?,
85        )
86    }
87}
88
89impl<'de, T, TAs> DeserializeAs<'de, T> for JsonString<TAs>
90where
91    TAs: for<'a> DeserializeAs<'a, T>,
92{
93    fn deserialize_as<D>(deserializer: D) -> Result<T, D::Error>
94    where
95        D: Deserializer<'de>,
96    {
97        struct Helper<S, SAs>(PhantomData<(S, SAs)>);
98
99        impl<S, SAs> Visitor<'_> for Helper<S, SAs>
100        where
101            SAs: for<'a> DeserializeAs<'a, S>,
102        {
103            type Value = S;
104
105            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
106                formatter.write_str("valid json object")
107            }
108
109            fn visit_str<E>(self, value: &str) -> Result<S, E>
110            where
111                E: DeError,
112            {
113                serde_json::from_str(value)
114                    .map(DeserializeAsWrap::<S, SAs>::into_inner)
115                    .map_err(DeError::custom)
116            }
117        }
118
119        deserializer.deserialize_str(Helper::<T, TAs>(PhantomData))
120    }
121}
serde_with/json.rs

serde_with/
json.rs
