diesel-enum-number

Maps Rust enums with explicit integer discriminants to PostgreSQL SMALLINT columns via diesel. This code was adapted from a declarative macro that worked the same way but was not available as an attribute which became a bit of a pain when leveraging with type generation via typeshare due to limitations with attaching the attribute to the generated enum.

Usage

use diesel_enum_number::diesel_enum_number;

#[diesel_enum_number]
// serde not required, but can fit in well with this approach
#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
#[serde(rename_all = "SCREAMING_SNAKE_CASE")]
pub enum UserStatus {
    Active = 1,
    Inactive = 2,
    Pending = 3,
}

/// expands to:
/// #[repr(i16)]
/// #[derive(diesel::AsExpression, diesel::FromSqlRow)]
/// #[diesel(sql_type = diesel::sql_types::SmallInt)]
/// #[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
/// #[serde(rename_all = "SCREAMING_SNAKE_CASE")]
/// pub enum UserStatus {
///     Active = 1,
///     Inactive = 2,
///     Pending = 3,
/// }
/// // + ToSql, FromSql, and from_i16 impls

The enum can then be used directly in diesel structs and queries:

#[derive(Queryable, Insertable)]
#[diesel(table_name = users)]
pub struct User {
    pub id: i32,
    pub status: UserStatus,
}

users::table
.filter(users::status.eq(UserStatus::Active))
.load::<User>(conn) ?;

vs. diesel-derive-enum

diesel-derive-enum maps Rust enums to PostgreSQL native enum types ( CREATE TYPE status AS ENUM ('active', 'inactive')), which are string-based. This crate instead supports using small integer-based enum approach, deferring the meaning of the values to the application layer as well as avoiding migrations when making changes to existing enums etc.

Backend support

Currently only PostgreSQL is supported. Support for MySQL and SQLite may be added in a future release.

License

MIT