Canister events

Developers
2

A couple of drive-by comments:

  • Candid is higher-order, so you can make SubscriptionRequest properly typed by passing real method handles of type (PublisherMessage) → () instead of a canister/method records.

  • Why have the indirection through the SubscriptionRequest type instead of two methods?

    type Publisher = service {
  icrc6_subscribe : (handler : (PublisherMessage) → ()) → (SubscriptionResponse);
  icrc6_unsubscribe : (handler : (PublisherMessage) → ()) → (SubscriptionResponse);
}

  • If you want the SubscriptionError type to be extensible in the future (without breaking clients), you need to wrap it in an option:

    type SubscriptionResponse = variant {
  Ok;
  Err : opt SubscriptionError;
};

    This wat, when you later add a new case to the error type, an old client will continue to work and just see null.

  • The same for PublisherNotification.

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