Review: the error that is not the error

export interface Plugin {
  name: string
  setup?: (app: App) => void
  hooks?: Record<string, (app: App) => void>
}

export interface App {
  provided: Record<string, unknown>
  hooks: Record<string, Array<(app: App) => void>>
  provide: (key: string, value: unknown) => void
  callHook: (name: string) => void
}

export function createApp(plugins: Plugin[]): App {
  const app: App = {
    provided: {},
    hooks: {},
    provide(key, value) {
      app.provided[key] = value
    },
    callHook(name) {
      for (const hook of app.hooks[name] ?? []) hook(app)
    },
  }

  applyPlugins(app, plugins)
  return app
}

function applyPlugins(app: App, plugins: Plugin[]): void {
  for (const plugin of plugins) {
    for (const [name, hook] of Object.entries(plugin.hooks ?? {})) {
      app.hooks[name] ??= []
      app.hooks[name].push(hook)
    }
  }

  for (const plugin of plugins) {
    plugin.setup?.(app)
  }
}