Fix a bad `dataState` value when an error occurs on a deferred field that bubbles to the defer boundary by jerelmiller · Pull Request #13376 · apollographql/apollo-client

jerelmiller · 2026-07-31T22:02:31Z

While working on an experiment for an unrelated issue, I stumbled upon this behavior. Currently an error reported by a @defer field that bubbles to the defer boundary reports the final chunk to the user as complete instead of streaming even though the result still has the hole in the data. This fix unconditionally applies the diff data to result when the dataState is streaming rather than only applying to when hasNext is true. This makes sure the final chunk delivers the right dataState value.

Summary by CodeRabbit

Bug Fixes
- Fixed @defer queries incorrectly reporting a complete state when deferred-field errors occur.
- Streaming results now remain marked as streaming while additional data may still arrive.
- Streamed data and associated errors are preserved correctly in the final payload.

…ndary works as expected

apollo-librarian · 2026-07-31T22:02:34Z

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Build ID: 22d78122423c4ea713325a69
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URL: https://www.apollographql.com/docs/deploy-preview/22d78122423c4ea713325a69

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changeset-bot · 2026-07-31T22:02:35Z

🦋 Changeset detected

Latest commit: f0431c5

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

This PR includes changesets to release 1 package

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@apollo/client	Patch

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coderabbitai · 2026-07-31T22:03:02Z

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

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Run ID: c1ef014c-ba49-4d1b-8205-3ba1a85092eb

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Reviewing files that changed from the base of the PR and between 48f7386 and f0431c5.

📒 Files selected for processing (3)

.changeset/loud-bulldogs-pay.md
src/core/QueryInfo.ts
src/incremental/handlers/__tests__/graphql17Alpha9/defer.test.ts

📝 Walkthrough

Walkthrough

The change preserves dataState: "streaming" for @defer results when deferred-field errors reach the defer boundary. QueryInfo accepts streaming cache diffs without requiring hasNext, and the defer test expectations now cover streamed data, errors, and partial results.

Changes

Deferred streaming state

Layer / File(s)	Summary
Preserve streaming state through cache results and tests `src/core/QueryInfo.ts`, `src/incremental/handlers/__tests__/graphql17Alpha9/defer.test.ts`, `.changeset/loud-bulldogs-pay.md`	`QueryInfo` accepts streaming cache diffs without requiring `hasNext`. The defer test keeps the final result streaming with `NetworkStatus.error` and `partial: true`. A patch changeset documents the fix.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

apollographql/apollo-client#13324: Both modify QueryInfo.markQueryResult and incremental @defer dataState handling.
apollographql/apollo-client#13347: Both preserve dataState: "streaming" in incremental cache handling.
apollographql/apollo-client#13360: Both modify incremental cache and diff handling in QueryInfo.

Suggested labels: auto-cleanup

Suggested reviewers: phryneas, daleseo

Poem

A rabbit watched the payload flow,
“Keep streaming,” said the data below.
Errors reached the defer gate,
But completion had to wait.
Tests now guard the proper state—
Hop, hop, fixed at last!

🚥 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 clearly and concisely describes the fix for the incorrect `dataState` value caused by errors on deferred fields.
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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src/core/QueryInfo.ts

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src/incremental/handlers/__tests__/graphql17Alpha9/defer.test.ts

ESLint skipped: the ESLint configuration for this file references a package that is not available in the sandbox.

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pkg-pr-new · 2026-07-31T22:04:24Z

npm i https://pkg.pr.new/@apollo/client@13376

commit: f0431c5

jerelmiller added 2 commits July 31, 2026 14:27

Always apply streaming result so that errors that bubble to defer bou…

e1b22f6

…ndary works as expected

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f0431c5

jerelmiller requested a review from phryneas July 31, 2026 22:02

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Fix a bad `dataState` value when an error occurs on a deferred field that bubbles to the defer boundary - #13376

Fix a bad `dataState` value when an error occurs on a deferred field that bubbles to the defer boundary#13376
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jerel/fix-data-state-streaming-error

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