[Proposal] type sizes in diesel schema

[trsh]

In my application (REST, GraphQL, etc.) I want field restrictions being closely tighten up with DB field restrictions. For example, if a DB field is Varchar(100), then my application should also push restriction of 100 symbols for a input, that will be stored in this field.

Right now I have to control this manually. If I change DB field size restriction via migrations, I have to remember also to change restrictions in my application.

Solution. let the generated Schema include also sizes:

table! {
    constants (id) {
        id -> Varchar(20),
        created_at -> Timestamp,
        updated_at -> Nullable<Timestamp>,
        .....
    }
}

And let this size be accessible via .dsl::id.size() (orsmth like that).

[sgrif]

Thanks, but this isn't something I want to have Diesel care about or try to enforce right now. This is no different than other forms of constraints. You can just as easily have an arbitrary check constraint that we have no way of handling. Additionally, we have no way to try and enforce this at compile time. There's no type that represents a fixed length string in Rust.