ClassSpawnArgs

ClassSpawnArgs<E> = [SetupParamTuple<E>] extends [never] ? [SpawnOptions] : SetupParamTuple<E> extends readonly [] ? [SpawnOptions] : [] extends SetupParamTuple<E> ? [SetupParams<E>, SpawnOptions] : [SetupParams<E>, SpawnOptions]

Defined in: Scene.ts:98

Trailing arguments of the class form of spawn / spawnChild, derived from the entity’s setup() signature. An omitted required field is reported as a missing property on the params type.

The params slot follows the setup PARAMETER, not the param object’s fields:

• no declared setup → only the trailing options slot.
• setup(): void with zero parameters → no params slot; behaves like a class with no declared setup, so spawn(Class, options?).
• setup(params?) or a defaulted parameter (a zero-argument call is valid, so [] is assignable to the parameter tuple) → params slot optional.
• setup(params) with a required parameter → params slot required, even when the param object’s own fields are all optional. setup(undefined) at runtime would break a body that reads params, so the type demands the argument.

The zero-parameter branch (SetupParamTuple<E> extends readonly []) must precede the optional-parameter branch: an exactly-empty tuple [] is assignable to readonly [], while an optional-first-parameter tuple [X?] is not, so the check catches only a genuine zero-arg setup and leaves setup(params?) to the branch below.

The params slot is typed as SetupParams<E> alone (not SetupParams<E> | SpawnOptions), so a SpawnOptions-shaped object is not silently accepted where params belong. The one residual: if the param type itself declares an optional key, a { key } literal satisfies the slot and the runtime routes it to options — the “don’t name a top-level setup field key” footgun documented on SpawnOptions.key. Use the explicit 3-arg form.

Type Parameters

E

E