Add tests to check whether read function values are returned for incremental results

[jerelmiller]

While implementing the incremental fixes in #13324, I noticed another case we aren't handling correctly with incremental streaming: read functions are run, but the results are never applied to intermediate incremental results. cache.diff runs the read functions, but because we only apply diff.result when diff.complete (which is false when @defer chunks haven't streamed yet), we never see the transformed values.

I want to make sure #13324 fixes most (if not all) of these cases, so I'm creating a separate test suite for this. These tests are added in a separate file to avoid conflicts with the test file changes from #13324. That PR will be remove this test file and copy over the tests to maintain a clean merge.

Summary by CodeRabbit

• Tests
  • Added comprehensive coverage for incremental GraphQL delivery using @defer and @stream.
  • Validated cache field transformations across partial results, streamed list items, nested objects, overlapping selections, and residual cache data.
  • Documented expected behavior for scenarios still under development.

[apollo-librarian]

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Build ID: 7c9694eb96c819f309dcfaa4
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Latest commit: d8de22d

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[jerelmiller]

Many of these are test.failing (which I expected). .failing will be removed in #13324.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI (base), Organization UI (inherited)

Review profile: CHILL

Plan: Pro

Run ID: 14b139cc-e63a-4ea5-924e-629c8cf3d593

📥 Commits

Reviewing files that changed from the base of the PR and between b021583 and d8de22d.

📒 Files selected for processing (1)

• src/core/__tests__/client.watchQuery/cacheFieldReadIncrementalGraphQL17Alpha9.test.ts

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📝 Walkthrough

Walkthrough

Adds a GraphQL 17 Alpha 9 incremental delivery test suite covering cache field read functions across deferred fields, streamed lists, partial cache data, residual fills, overlapping selections, and nested objects.

Changes

Incremental cache field reads

Layer / File(s)	Summary
Deferred cache read scenarios src/core/__tests__/client.watchQuery/cacheFieldReadIncrementalGraphQL17Alpha9.test.ts	Adds helpers and tests for read functions across deferred streaming, partial cache merges, overlapping selections, and residual cache completion.
Streamed list cache reads src/core/__tests__/client.watchQuery/cacheFieldReadIncrementalGraphQL17Alpha9.test.ts	Tests read-function application to streamed list items, partial cached lists, and residual complete items.
Nested streamed selections src/core/__tests__/client.watchQuery/cacheFieldReadIncrementalGraphQL17Alpha9.test.ts	Tests read functions for nested objects with overlapping streamed and non-streamed fields.

Estimated code review effort: 4 (Complex) | ~45 minutes

Poem

I’m a bunny with chunks in my queue,
Watching cached fields turn bright and new.
Deferred bits hop, streams gently flow,
Nested reads bloom as the results grow.
Some tests pass, some failures say,
“More cache magic is on its way!”

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the new tests for cache read behavior in incremental results.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[pkg-pr-new]

npm i https://pkg.pr.new/@apollo/client@13333

commit: d8de22d