Quick question that I haven’t thought out yet but ...

# apollo-kotlin

[wasyl]

Quick question that I haven’t thought out yet but I’m wondering if you have: we’re using Apollo’s cache to keep single source of truth for majority of the data in the app. This works very well, but sometimes we have data that we’d very much like to always have available. We would fetch it when the user logs in and then the app could operate under assumption that observing the query will emit cached value immediately.

This works until we update the query and start fetching a new field for example. Now, Apollo can’t emit any value, so it emits null and refetches the query. Have you ever thought about some way to do migrations for the cached state of the queries, such that the app can continue working while offline? Such migrations could compute the default values or insert empty/null objects that the query will use for the time being, until it’s refetched

[mbonnin]

I think what we'd want to do there is the cache to return partial results and a list of errors (similar to what a real server would do)

[mbonnin]

Then the UI can decide to display a default state or if it can't, display an error message

[wasyl]

Having such partial results would imply each field from the query would be nullable, right?

[mbonnin]

Mmmm right

[mbonnin]

If not it "bubbles" up and you start losing data

[mbonnin]

We could have an @optional directive that is the opposite of @nonnull for these cases

[mbonnin]

Another option would be to leverage the CacheResolver API. You can technically add code there to "recover" from a cache miss

[wasyl]

I realize any API would have to be carefully thought out, to be convenient to use but not overly complex. Anyway just wanted to throw the idea, I’m not even sure how specific to our use case it is

[mbonnin]

Yea, the CacheResolver API is complex...