[Explainer] Using toDynamicValue() without an explicit scope can lead to performance issues

[mscharley]

Unless configured differently, the default scope for a container is transient scope. This means that every request to the container which needs this binding will run your dynamic binding again every time it is needed in that request which can quickly become a performance bottleneck if that request is on a hot path in your application. Consider using a more cacheable scope for your dynamic bindings if possible, however any explicit scope for the binding will silence the warning.

const module: interfaces.ContainerModule = (bind) => {
  const factory = async () => { 
    await sleep(500);
    return "Hello world!";
  };

  // Will generate a warning
  bind(token).toDynamicValue(factory);

  // Will not generate a warning
  bind(token).inTransientScope().toDynamicValue(factory);
  bind(token).inRequestScope().toDynamicValue(factory);
  bind(token).inSingletonScope().toDynamicValue(factory);
}