one/src/platform/app-intents/validate.ts

One is a React framework for web, iOS, and Android apps.

export function assertActionHandler(identifier: string, handler: unknown): void {
  if (typeof identifier !== 'string' || !identifier.trim() || typeof handler !== 'function') {
    throw new TypeError('AppIntents.defineAction requires a non-empty identifier and a function')
  }
}