The 3.0 migration doc mentions: “Watchers now default to a

CacheOnly

refetchPolicy instead

CACHE_FIRST

. To keep behavior unchanged, set a

refetchPolicy

on your watchers:” But the snippet directly under it shows

subscribe

instead of

watch()

. Is this wrong in the sense that it should be

.watch()

instead, or should the title of the section be

subscriptions

? I am kinda confused at that part of the document.

I have no idea what happened in my brain when I typed this... Sorry about this. Watchers are for queries, not subscriptions. It should be

.query(query).watch()

... Fix there: https://github.com/apollographql/apollo-kotlin/pull/4118/files

Hey it’s a small mistake, don’t worry about it 🤗 I do have a question regarding this though then. Looking at the code, watch internally does a toFlow() and then emits the response directly. And only after that it does the copy() with the cache_only policy. Which part am I missing that makes the watch do as the docs suggest aka only fetch from the cache? Also as a side curiosity question, if we had not configured any cache (http or normalized) would a

watch

just do nothing?

Looking at the code, watch internally does a toFlow() and then emits the response directly.

That's for the initial response only. If you follow the code, you'll see another lower level

watch

that watches for changed keys in the store

if we had not configured any cache (http or normalized) would a

watch

just do nothing?

It would return the

NetworkOnly

response once and that's it.

Aha does that mean that before, the refetch was CACHE_FIRST aka if there was a cache miss it would try and hit the network?

Yes, exactly

Wow yeah very interesting I had no idea! Yeah I missed the part where it said “refetchPolicy” so I didn’t piece the two things together. Thanks a lot for the clarification! I think I have the correct understanding to move forward with this 🙌

There's another lower-level watch() in this file that is not advertized as much because it's a lot newer but has less "logic" inside and exposes what is (I believe) a simpler API

Yeah I noticed that one too, but I am not sure I understood it exactly. What are you referring to when you say “initial set of keys”? And how is the

data: D?

used in that function? Just looking at the function signature I assume you pass what the first emission of watch will return, and from then on it will return all cache changes, but I am not sure. And as a side note, In all the times I had to use a watch myself, I did in fact want the behavior of fetch once, and listen after, but I imagine there are other use-cases that don’t have the same requirements. But we’re not relying super much on caching in general, so there’s that.

data

is used to get the initial set of keys to watch for