QueryResult.fetchMore() triggers unexpected refetch of indirectly related "cache-and-network" queries

[zenflow]

Intended outcome:
When I call query.fetchMore() I expect this to never affect other queries or cause the other queries to be refetched.

Actual outcome:

When I call query.fetchMore() it sometimes causes a refetch of some "cache-and-network" query on the page.

It seems to happen when both queries (the one for which we call query.fetchMore() and the one that uses fetchPolicy: "cache-and-network") request data inside a common object type (e.g. __typename: "User").

How to reproduce the issue:

1. Create or find an AC app where query.fetchMore() is used on a query that shares data with other queries shown on-screen
2. Change the fetchPolicy for the other queries to "cache-and-network"
3. Start the app, open it, open the network tab in Chrome devtools
4. Trigger the query.fetchMore() in the app
5. Observe that the other queries (which were set to "cache-and-network") are refetched after first (expected) request

Versions
@apollo/client v3.3.13

[Akryum]

Maybe related to #6916

[zenflow]

@Akryum Definitely somewhat related. I actually had noticed that issue too but with so many things going wrong I didn't document them all.

I'm able to work around that issue by adding nextFetchPolicy: "cache-first" wherever I'm using fetchPolicy: "cache-and-network", but sadly that doesn't help with this issue.

[sebastienbarre]

I'm able to work around that issue by adding nextFetchPolicy: "cache-first" wherever I'm using fetchPolicy: "cache-and-network", but sadly that doesn't help with this issue.

I can observe that as well in 3.4.16, this is unfortunate.

[gastonmorixe]

Spent 48 hours trying to understand why after executing fetchMore I had duplicate network requests. Sadly this happens with cache-and-network and network-only, be sure to set nextFetchPolicy: "cache-first"

Using v3.5.5

[benjamn]

This does sound like the same issue as #6916—see my thoughts in #6916 (comment).

The central idea is that complete cache results (broadcast after a successful fetchMore, for example) should be delivered immediately, by themselves, without triggering a network request for fetch policies like cache-and-network or network-only. Setting nextFetchPolicy: "cache-first" is a good workaround in the meantime because cache-first similarly avoids the network given a complete cache result.

I am actively working on that issue for v3.6. Unfortunately there are a number of test differences to work through, and those disruptions (even if they're ultimately improvements, like fewer network requests) needed more intensive beta testing than we thought we could get before v3.5 was released. I'm still hopeful it will be safe for a minor release (rather than AC4).

Closing this as a duplicate (please join the discussion in #6916), but happy to reopen if my planned changes don't (seem like they will) solve the whole problem here as well.

[gastonmorixe]

thank you @benjamn