diesel 2.3.8

A safe, extensible ORM and Query Builder for PostgreSQL, SQLite, and MySQL
Documentation 
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use crate::deserialize::{self, FromSql};
use crate::mysql::{Mysql, MysqlValue};
use crate::serialize::{self, IsNull, Output, ToSql};
use crate::sql_types;

#[cfg(all(feature = "mysql_backend", feature = "serde_json"))]
impl FromSql<sql_types::Json, Mysql> for serde_json::Value {
    fn from_sql(value: MysqlValue<'_>) -> deserialize::Result<Self> {
        serde_json::from_slice(value.as_bytes()).map_err(|_| "Invalid Json".into())
    }
}

#[cfg(all(feature = "mysql_backend", feature = "serde_json"))]
impl ToSql<sql_types::Json, Mysql> for serde_json::Value {
    fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> serialize::Result {
        serde_json::to_writer(out, self)
            .map(|_| IsNull::No)
            .map_err(Into::into)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    #[diesel_test_helper::test]
    fn json_to_sql() {
        use crate::query_builder::bind_collector::ByteWrapper;

        let mut buffer = Vec::new();
        let mut bytes = Output::test(ByteWrapper(&mut buffer));
        let test_json = serde_json::Value::Bool(true);
        ToSql::<sql_types::Json, Mysql>::to_sql(&test_json, &mut bytes).unwrap();
        assert_eq!(buffer, b"true");
    }

    #[diesel_test_helper::test]
    fn some_json_from_sql() {
        use crate::mysql::MysqlType;
        let input_json = b"true";
        let output_json: serde_json::Value = FromSql::<sql_types::Json, Mysql>::from_sql(
            MysqlValue::new_internal(input_json, MysqlType::String),
        )
        .unwrap();
        assert_eq!(output_json, serde_json::Value::Bool(true));
    }

    #[diesel_test_helper::test]
    fn bad_json_from_sql() {
        use crate::mysql::MysqlType;
        let uuid: Result<serde_json::Value, _> = FromSql::<sql_types::Json, Mysql>::from_sql(
            MysqlValue::new_internal(b"boom", MysqlType::String),
        );
        assert_eq!(uuid.unwrap_err().to_string(), "Invalid Json");
    }

    #[diesel_test_helper::test]
    fn no_json_from_sql() {
        let uuid: Result<serde_json::Value, _> =
            FromSql::<sql_types::Json, Mysql>::from_nullable_sql(None);
        assert_eq!(
            uuid.unwrap_err().to_string(),
            "Unexpected null for non-null column"
        );
    }
}