How to impl ToSql for Serialized struct using serde_json in diesel 2.0

[lisiur]

#[derive(AsExpression, FromSqlRow, Debug)]
#[diesel(sql_type = Text)]
pub struct JsonWrapper<T: serde::de::DeserializeOwned + serde::Serialize + fmt::Debug>(pub T);

impl<T: serde::de::DeserializeOwned + serde::Serialize + fmt::Debug> FromSql<Text, Sqlite>
    for JsonWrapper<T>
{
    fn from_sql(bytes: diesel::backend::RawValue<'_, Sqlite>) -> diesel::deserialize::Result<Self> {
        let bytes = <Vec<u8>>::from_sql(bytes)?;
        let inner = serde_json::from_slice::<T>(&bytes)?;
        Ok(JsonWrapper(inner))
    }
}

impl<T: serde::de::DeserializeOwned + serde::Serialize + fmt::Debug> ToSql<Text, Sqlite>
    for JsonWrapper<T>
{
    fn to_sql<'b>(
        &'b self,
        out: &mut diesel::serialize::Output<'b, '_, Sqlite>,
    ) -> diesel::serialize::Result {
        todo!()
    }
}

I have tried this:

<str as ToSql<Text, Sqlite>>::to_sql(&serde_json::to_string(&self.0).unwrap(), out)

but the complier complains that: temporary value dropped while borrowed creates a temporary value which is freed while still in use.

From what I understand, serde_json does not support returning a reference, so could someone provide assistance with resolving this issue?

[weiznich]

See the relevant section of the migration guide or the documentation of ToSql for information on how to resolve these kind of issues.

[lisiur]

Thank you for your reply. I apologize for not thoroughly reading the documentation beforehand.

Here is my workaround for those encountering a similar issue.

out.set_value(serde_json::to_string(&self.0).unwrap());
Ok(IsNull::No)

[yasamoka]

Just leaving this here for anyone who has this issue - in my case, &mut out.reborrow() was the solution.