"Generated" is created in output, but Kysely has this type

[Matthias Feist]

I noticed that when I run the codegen, I get the following lines in my output file:

export type Generated<T> = T extends ColumnType<infer S, infer I, infer U>
  ? ColumnType<S, I | undefined, U>
  : ColumnType<T, T | undefined, T>;

However, Kysely already exports a "Generated" type via import type { Generated } from 'kysely';, so I was wondering why codegen is creating its own type?

[RobertHunter-Pluto]

I noticed the same thing and was wondering why. The Kysely version of Generated looks like it doesn't account for T possibly already being an instance of ColumnType the way this one does, but I haven't quite figured out why yet. Looks like ColumnType in Kysely defaults the S, I, and U parameters there to SelectType anyways, so it maybe it works out the same?

Definitely doesn't seem to be a problem, just interested in understanding the codebase a little better.

[Robin Blomberg]

Oh right! I knew I added my own Generated implementation for a reason.

Some types already use ColumnType:

export type Json = ColumnType<JsonValue, string, string>;

export type Timestamp = ColumnType<Date, Date | string, Date | string>;

So this special type is necessary in order to do this:

export interface User {
  created_at: Generated<Timestamp>;
//            ^ ColumnType<Date, Date | string | undefined, Date | string>
}

Otherwise the type would be equal to this monstrosity:

export interface User {
  created_at: Generated<Timestamp>;
//            ^ ColumnType<
//                ColumnType<Date, Date | string, Date | string>,
//                ColumnType<Date, Date | string, Date | string> | undefined,
//                ColumnType<Date, Date | string, Date | string>
//              >
}

[Shane]

I just ran into this issue as I had removed it thinking it was in conflict/redundant to kysely's Generated type. Any appetite for renaming the Generated type codegen spits out to maybe something that describes the intent / difference?