mysql: Add JSON support

sqlx-core/src/mysql/types/json.rs

@@ -0,0 +1,58 @@
+use crate::decode::Decode;
+use crate::encode::Encode;
+use crate::mysql::database::MySql;
+use crate::mysql::protocol::TypeId;
+use crate::mysql::types::*;
+use crate::mysql::{MySqlTypeInfo, MySqlValue};
+use crate::types::{Json, Type};
+use serde::{Deserialize, Serialize};
+use serde_json::Value as JsonValue;
+
+impl Type<MySql> for JsonValue {
+    fn type_info() -> MySqlTypeInfo {
+        <Json<Self> as Type<MySql>>::type_info()
+    }
+}
+
+impl Encode<MySql> for JsonValue {
+    fn encode(&self, buf: &mut Vec<u8>) {
+        (Box::new(Json(self)) as Box<dyn Encode<MySql>>).encode(buf)
+    }
+}
+
+impl<'de> Decode<'de, MySql> for JsonValue {
+    fn decode(value: MySqlValue<'de>) -> crate::Result<Self> {
+        <Json<Self> as Decode<MySql>>::decode(value).map(|item| item.0)
+    }
+}
+
+impl<T> Type<MySql> for Json<T> {
+    fn type_info() -> MySqlTypeInfo {
+        // MySql uses the CHAR type to pass JSON data from and to the client
+        MySqlTypeInfo::new(TypeId::CHAR)
+    }
+}
+
+impl<T> Encode<MySql> for Json<T>
+where
+    T: Serialize,
+{
+    fn encode(&self, buf: &mut Vec<u8>) {
+        let json_string_value =
+            serde_json::to_string(&self.0).expect("serde_json failed to convert to string");
+        <str as Encode<MySql>>::encode(json_string_value.as_str(), buf);
+    }
+}
+
+impl<'de, T> Decode<'de, MySql> for Json<T>
+where
+    T: 'de,
+    T: for<'de1> Deserialize<'de1>,
+{
+    fn decode(value: MySqlValue<'de>) -> crate::Result<Self> {
+        let string_value = <&'de str as Decode<MySql>>::decode(value).unwrap();
+        serde_json::from_str(&string_value)
+            .map(Json)
+            .map_err(crate::Error::decode)
+    }
+}

sqlx-core/src/mysql/types/mod.rs

@@ -47,6 +47,13 @@
 //! | Rust type                             | MySQL type(s)                                        |
 //! |---------------------------------------|------------------------------------------------------|
 //! | `bigdecimal::BigDecimal`              | DECIMAL                                              |
+//! ### [`json`](https://crates.io/crates/json)
+//!
+//! Requires the `json` Cargo feature flag.
+//!
+//! | Rust type                             | MySQL type(s)                                        |
+//! |---------------------------------------|------------------------------------------------------|
+//! | `json::JsonValue`             | JSON
 //!
 //! # Nullable
 //!
@@ -70,6 +77,9 @@ mod chrono;
 #[cfg(feature = "time")]
 mod time;
 
+#[cfg(feature = "json")]
+mod json;
+
 use crate::decode::Decode;
 use crate::mysql::{MySql, MySqlValue};
 

sqlx-core/src/postgres/types/json.rs

@@ -23,7 +23,7 @@ impl Type<Postgres> for JsonValue {
 
 impl Encode<Postgres> for JsonValue {
     fn encode(&self, buf: &mut PgRawBuffer) {
-        Json(self).encode(buf)
+        (Box::new(Json(self)) as Box<dyn Encode<Postgres>>).encode(buf)
     }
 }
 
@@ -41,7 +41,7 @@ impl Type<Postgres> for &'_ JsonRawValue {
 
 impl Encode<Postgres> for &'_ JsonRawValue {
     fn encode(&self, buf: &mut PgRawBuffer) {
-        Json(self).encode(buf)
+        (Box::new(Json(self)) as Box<dyn Encode<Postgres>>).encode(buf)
     }
 }