Fields without @client directive should not be resolved locally

[vladar]

Description

This PR fixes an incorrect behavior when local resolvers are executed even for fields without a @client directive. Reproduction is in the PR tests. This happens because Apollo walks through every single selectionSet in LocalState without checking if this selectionSet actually has a @client directive.

This problem also affects query performance significantly in some cases, see the benchmark.

For server GraphQL results like this:

{
  items: [
    { id: "0", foo: "foo-0" },
    { id: "1", foo: "foo-1" },
    // ...
    { id: "99", foo: "foo-99" },
  ]
  serverOrClient: `server`
}

The benchmark shows the following numbers:

Without client resolver (baseline)
100 items x 1,078 ops/sec ±4.69% (58 runs sampled)
1000 items x 128 ops/sec ±5.05% (57 runs sampled)
10000 items x 11.90 ops/sec ±8.81% (55 runs sampled)

With client resolver (before the PR)
100 items x 494 ops/sec ±7.05% (59 runs sampled)
1000 items x 56.21 ops/sec ±6.67% (56 runs sampled)
10000 items x 5.10 ops/sec ±10.75% (28 runs sampled)

With client resolver (after the PR)
100 items x 1,002 ops/sec ±7.57% (60 runs sampled)
1000 items x 123 ops/sec ±7.82% (55 runs sampled)
10000 items x 12.80 ops/sec ±8.15% (58 runs sampled)

Fixes #9571

[apollo-cla]

@vladar: Thank you for submitting a pull request! Before we can merge it, you'll need to sign the Apollo Contributor License Agreement here: https://contribute.apollographql.com/

[vladar]

@benjamn @brainkim A gentle ping on this PR - performance implications of even a single @client field are quite significant (especially noticeable for frequent subscriptions with big payloads). I think it deserves to be addressed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 03f30f2

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@apollo/client	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[jerelmiller]

Hey @vladar 👋 !

Thanks so much for your patience. I really like the work you've done here and think this will be a tremendous improvement to the client. I've left only minor bits of feedback for you, but overall really like the strategy you took here. Glad its also been confirmed that this solution works for others. I'd like to get this merged as soon as you're able to address some of the feedback. Thanks again for the contribution!

[jerelmiller]

@vladar thanks so much again for the contribution! Looking forward to getting this released 🎉 🎉