The typing of class `SceneContextScene` is incorrect

Author: EverttCreated Apr 9, 2023Updated May 5, 2026

Labelsenhancement

Context

So I have this:

typescript

type SceneSessionData = {
    current?: string
    expires?: number
    state?: {
        lastMessageId?: number
    }
}

type MyContext = Context & {
    session: {
        __scenes?: SceneSessionData
    }
    scene: Scenes.SceneContextScene<MyContext, SceneSessionData>
}

And then looking at the implementation of the class SceneContextScene I see this code:

typescript

    get state() {
        return (this.session.state ??= {})
    }

    set state(value) {
        this.session.state = { ...value }
    }

But then the type definition of the class in typings/scenes/context.d.ts shows this:

typescript

export default class SceneContextScene<C extends SessionContext<SceneSession<D>>, D extends SceneSessionData = SceneSessionData> {
	// ...
    get session(): D;
    get state(): object;
    set state(value: object);
    // ...
}

Which means that when I do const state = ctx.scene.state, I'd expect state to be of type { lastMessageId?: number }, because that's what it actually is, but because of the type definition state is given with type object.

Solution

Change src/scenes/context.ts to this:

typescript

export default class SceneContextScene<C extends SessionContext<SceneSession<D>>, D extends SceneSessionData = SceneSessionData> {
    // ...
    get session(): D;
    get state(): D["state"];
    set state(value: D["state"]);
    // ...
}

And then I assume typings/scenes/context.d.ts will automatically be generated correctly.

Source: telegraf/telegraf

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