Drop limitation of disallowing generics for the TypedPath derive in axum-extra

[JustusFluegel]

Motivation

So I've recently tried to create a generic axum handler for any sea-orm Entity, which allows me to for example fetch it. Since a specific entity would not necessarily be indexed by the same primary key type, I wanted to be generic over that as well, which was when I noticed the TypedPath derive doesn't support generic params yet.

Example

#[allow(type_alias_bounds)]
pub type IdType<T>
where
    T: EntityTrait,
= <T::PrimaryKey as PrimaryKeyTrait>::ValueType;

#[derive(TypedPath, Deserialize)]
#[typed_path("/:id")]
pub struct GetById<T> {
    id: T,
}

pub async fn get_by_id<T: EntityTrait>(
    GetById { id }: GetById<IdType<T>>,
    State(AppState {
        database_connection,
        ..
    }): State<AppState>,
) -> impl IntoResponse {
    Json(
        T::find_by_id(id)
            .into_json()
            .one(&database_connection)
            .await
            .unwrap(),
    )
}

Solution

This removes the limitation in the proc-macro using the following 2 changes:

• Drop the check for generics from the macro
• Add the required generics & where bounds where needed