2 releases
0.1.1 | May 20, 2024 |
---|---|
0.1.0 | May 20, 2024 |
#343 in Procedural macros
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10KB
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diesel-json-derive
NOTE: This is under active development. No guarantees for stability or usability. You probably want diesel_json instead. Please also note that this currently expects postgres. Pull requests to support other backends are welcome.
diesel_json_derive
What's this? This is a procedural macro that automatically derives ToSql
and FromSql
for Diesel's Jsonb
type.
Consider a table like
CREATE TABLE foo (
id TEXT PRIMARY KEY,
bar JSONB NOT NULL
);
which is in Rust can be represented as as (does not compile!):
#[derive(Debug, Queryable, Identifiable, Insertable, AsChangeset, Selectable)]
#[diesel(table_name = crate::schema::foo)]
#[diesel(check_for_backend(diesel::pg::Pg))]
#[diesel(primary_key(id))]
struct Foo {
id: String,
bar: Bar,
}
struct Bar {
x: i32,
}
In order to make Bar
be represented as a jsonb blob you will need to implement the diesel::deserialize::FromSql
and diesel::deserialize::FromSql
traits, e.g. like this:
impl ToSql<Jsonb, Pg> for Foo {
fn to_sql<'b>(&'b self, out: &mut serialize::Output<'b, '_, Pg>) -> serialize::Result {
out.write_all(&[1])?;
serde_json::to_writer(out, &self)?;
Ok(serialize::IsNull::No)
}
}
impl FromSql<Jsonb, Pg> for Foo {
fn from_sql(bytes: PgValue<'_>) -> deserialize::Result<Self> {
let bytes = bytes.as_bytes();
if bytes[0] != 1 {
return Err("Unsupported JSONB encoding version".into());
}
serde_json::from_slice(&bytes[1..]).map_err(|_| "Invalid Json".into())
}
}
This gets tedious quickly so this create does it for you. So with this crate you can write:
use diesel::sql_types::Jsonb;
use diesel::{FromSqlRow, AsExpression};
use diesel_json_derive::DieselJsonb;
use serde::{Deserialize, Serialize};
#[derive(Debug, Serialize, Deserialize, AsExpression, FromSqlRow, DieselJsonb)]
#[diesel(sql_type = Jsonb)]
struct Bar {
x: i32,
}
diesel_json_derive vs ## diesel_json
The diesel_json crate solves the same problem but uses a wrapper type for it. This has the disadvantage that this type needs to be used when matching for example. This crate does not have this disadvantage.
License: MIT
Dependencies
~230–670KB
~16K SLoC