nextFetchPolicy function is not called sometimes

[jeel2308]

Issue Description

I am using latest version of apollo client v3.8.7.
I am providing default nextFetchPolicy function to update fetchPolicy, if query has fetchPolicy of cache-and-network. According to the docs, nextFetchPolicy function should be called after request is done(reason after-fetch) and when variables are changed (reason variables-changed).
However, nextFetchPolicy function is not called after variables are changed(with reason variables-changed). It is only called when request is done.
Here is the code snippet that I am using,

const client = new ApolloClient({
  cache: new InMemoryCache(),
  link: httpLink,
  defaultOptions: {
    watchQuery: {
      fetchPolicy: "cache-and-network",
      notifyOnNetworkStatusChange: true,
      nextFetchPolicy: (
        currentFetchPolicy,
        { reason, initialFetchPolicy, observable }
      ) => {
        if (reason === "variables-changed") {
          return initialFetchPolicy;
        }

        if (
          reason === "after-fetch" &&
          ["cache-and-network"].includes(currentFetchPolicy)
        ) {
          return "cache-only";
        }

        return currentFetchPolicy;
      }
    },

    query: {
      fetchPolicy: "network-only"
    }
  }
});

Issue is solved if I comment out code inside after-fetch condition, but it limits usability of nextFetchPolicy function.

Link to Reproduction

https://codesandbox.io/p/sandbox/eloquent-cori-2jngr7?file=%2Fsrc%2Findex.jsx

Reproduction Steps

• Change values from dropdown and check logs in console.

• Comment out code inside after-fetch condition in nextFetchPolicy function and check logs again.

• Current outcome:

  • NextFetchPolicy function is called with reason 'after-fetch' whenever request is completed and not called when variables are changed(with reason variables-changed).

• Intended outcome:

  • NextFetchPolicy function should be called whenever variables are updated. Then it should be called again, if variable change triggers request with reason after-fetch.

[bignimbus]

Hi @jeel2308 👋🏻 thanks for opening this issue!

Your reproduction includes the use of the graphql higher-order component, which is deprecated as of 2020 (see the relevant docs page). Have you seen this behavior with the currently-supported React API?

[jeel2308]

Hi @bignimbus, thanks for your reply.

I have updated reproduction to use useQuery instead of graphql . Issue is still observed.

[jeel2308]

Any update on this?

[phryneas]

Hi Patel,
I've taken a look, and this is caused by these lines:

apollo-client/src/core/ObservableQuery.ts

Lines 882 to 884 in 3f7eecb

	// If we're changing the fetchPolicy anyway, don't try to change it here
	// using applyNextFetchPolicy. The explicit options.fetchPolicy wins.
	options.fetchPolicy === oldFetchPolicy

I'll change this to a bug with a reproduction, but right now I can't give you a timeframe on a fix here, as we are in the middle of finalizing Apollo Client 3.9 right now.

[jeel2308]

Hi, any updates on this? If you are busy on upcoming release, then can I raise PR for it?

[phryneas]

I'll try to take a stab at this next week :)

[phryneas]

@jeel2308 you can give the PR release in #11626 a stab if it solves your problem :)

[jeel2308]

Sure. I will have look. Thank you for the update

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