1 files changed, 150 insertions, 0 deletions
diff --git a/third_party/rust/serde_with/src/json.rs b/third_party/rust/serde_with/src/json.rs
new file mode 100644
index 0000000000..699d31c8d2
--- /dev/null
+++ b/third_party/rust/serde_with/src/json.rs
@@ -0,0 +1,150 @@
+//! De/Serialization of JSON
+//!
+//! This modules is only available when using the `json` feature of the crate.
+
+use crate::{de::DeserializeAs, ser::SerializeAs};
+use serde::{de::DeserializeOwned, Deserializer, Serialize, Serializer};
+
+/// Serialize value as string containing JSON
+///
+/// The same functionality is also available as [`serde_with::json::JsonString`][crate::json::JsonString] compatible with the `serde_as`-annotation.
+///
+/// # Examples
+///
+/// ```
+/// # use serde::{Deserialize, Serialize};
+/// #
+/// #[derive(Deserialize, Serialize)]
+/// struct A {
+///     #[serde(with = "serde_with::json::nested")]
+///     other_struct: B,
+/// }
+/// #[derive(Deserialize, Serialize)]
+/// struct B {
+///     value: usize,
+/// }
+///
+/// let v: A = serde_json::from_str(r#"{"other_struct":"{\"value\":5}"}"#).unwrap();
+/// assert_eq!(5, v.other_struct.value);
+///
+/// let x = A {
+///     other_struct: B { value: 10 },
+/// };
+/// assert_eq!(
+///     r#"{"other_struct":"{\"value\":10}"}"#,
+///     serde_json::to_string(&x).unwrap()
+/// );
+/// ```
+pub mod nested {
+    use core::{fmt, marker::PhantomData};
+    use serde::{
+        de::{DeserializeOwned, Deserializer, Error, Visitor},
+        ser::{self, Serialize, Serializer},
+    };
+
+    /// Deserialize value from a string which is valid JSON
+    pub fn deserialize<'de, D, T>(deserializer: D) -> Result<T, D::Error>
+    where
+        D: Deserializer<'de>,
+        T: DeserializeOwned,
+    {
+        #[derive(Default)]
+        struct Helper<S: DeserializeOwned>(PhantomData<S>);
+
+        impl<'de, S> Visitor<'de> for Helper<S>
+        where
+            S: DeserializeOwned,
+        {
+            type Value = S;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+                write!(formatter, "valid json object")
+            }
+
+            fn visit_str<E>(self, value: &str) -> Result<S, E>
+            where
+                E: Error,
+            {
+                serde_json::from_str(value).map_err(Error::custom)
+            }
+        }
+
+        deserializer.deserialize_str(Helper(PhantomData))
+    }
+
+    /// Serialize value as string containing JSON
+    ///
+    /// # Errors
+    ///
+    /// Serialization can fail if `T`'s implementation of `Serialize` decides to
+    /// fail, or if `T` contains a map with non-string keys.
+    pub fn serialize<T, S>(value: &T, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        T: Serialize,
+        S: Serializer,
+    {
+        let s = serde_json::to_string(value).map_err(ser::Error::custom)?;
+        serializer.serialize_str(&*s)
+    }
+}
+
+/// Serialize value as string containing JSON
+///
+/// The same functionality is also available as [`serde_with::json::nested`][crate::json::nested] compatible with serde's with-annotation.
+///
+/// # Examples
+///
+/// ```
+/// # #[cfg(feature = "macros")] {
+/// # use serde::{Deserialize, Serialize};
+/// # use serde_with::{serde_as, json::JsonString};
+/// #
+/// #[serde_as]
+/// #[derive(Deserialize, Serialize)]
+/// struct A {
+///     #[serde_as(as = "JsonString")]
+///     other_struct: B,
+/// }
+/// #[derive(Deserialize, Serialize)]
+/// struct B {
+///     value: usize,
+/// }
+///
+/// let v: A = serde_json::from_str(r#"{"other_struct":"{\"value\":5}"}"#).unwrap();
+/// assert_eq!(5, v.other_struct.value);
+///
+/// let x = A {
+///     other_struct: B { value: 10 },
+/// };
+/// assert_eq!(
+///     r#"{"other_struct":"{\"value\":10}"}"#,
+///     serde_json::to_string(&x).unwrap()
+/// );
+/// # }
+/// ```
+#[derive(Copy, Clone, Debug, Default)]
+pub struct JsonString;
+
+impl<T> SerializeAs<T> for JsonString
+where
+    T: Serialize,
+{
+    fn serialize_as<S>(source: &T, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        crate::json::nested::serialize(source, serializer)
+    }
+}
+
+impl<'de, T> DeserializeAs<'de, T> for JsonString
+where
+    T: DeserializeOwned,
+{
+    fn deserialize_as<D>(deserializer: D) -> Result<T, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        crate::json::nested::deserialize(deserializer)
+    }
+}