[Core] 7.0.0 Add effect

[lobor]

Is your feature request related to a problem? Please describe. In V6, in my code i used RequestEffect for update cache when POST request success

client.addEffect(
  new RequestEffect({
    effectKey: createTodo.effectKey,
    onSuccess: (response) => {
      if (!response?.data) return;
      client.cache.update(
        getTodos,
        (prev) => {
          if (!prev?.data) return {};
          return { ...prev, data: [...prev.data, response.data] };
        }
      );
    },
  })
);

does not have similar mechanics on V7

[prc5]

Hey, @lobor I will work on the detailed migration guide this week - we introduced the Plugin instead of Effect. https://hyperfetch.bettertyped.com/docs/core/plugin

Plugin was made from the RequestEffect, but as a more "general" utility. You will be able to create let's say CachePlugin which will update caches for the requests of your choice. 👍🏻

https://hyperfetch.bettertyped.com/docs/api/core/Classes/Plugin#onrequestsuccess

export const CachePlugin = () => new Plugin({ name: "cache-plugin" }).onRequestSuccess(({ request, response }) => {
  if(request.queryKey === createTodo.queryKey) {
      client.cache.update(
        getTodos,
        (prev) => {
          if (!prev?.data) return {};
          return { ...prev, data: [...prev.data, response.data] };
        }
      );
  }
})

// In the directory with client
client.addPlugin(CachePlugin());

[lobor]

Thanks for the update and example!

However, this new approach feels a bit too generic for my use case. In V6, RequestEffect allowed me to directly attach cache updates to specific requests in a very targeted way.

With the new Plugin system, I’m concerned that:

I’ll end up writing a single plugin with many if/else statements to differentiate between routes/models, or

I’ll need to create many small plugins — one per request — which can be hard to scale and maintain.

It would be great to have a more granular API again, something like:

createTodo.lifecycle.onSuccess((response) => {
  if (!response?.data) return;
  client.cache.update(
    getTodos,
    (prev) => {
      if (!prev?.data) return {};
      return { ...prev, data: [...prev.data, response.data] };
    }
  );
});

This would allow request-specific logic without needing to manage multiple plugins or complex conditional logic inside one.

Is something like this planned or possible with the current architecture?

[prc5]

This is very interesting use case, thank you for the example and explanations. I will make some way to handle side-effects in more atomic approach. 👍🏻 💯

[lobor]

Hi, any idea when the feature will be deployed? This is what we need to upgrade to v7

[prc5]

@lobor We're still discussing how to revive this functionality, but unfortunately the previous version (even in your example) was used in a way that was quite problematic – we're talking about circular dependencies. I think we'll eventually drop the option to support Flux-like approach in effects. This will significantly simplify the experience, and the previous functionality we wanted to preserve will be available through plugins.

I think we will start developing it really soon after finalizing tests and development of our "fetch" adapter - I guess plus-minus month, since the team will leave for vacations on September 🌞