fix(table-core): preserve grouped flatRows preorder by KevinVandy · Pull Request #6576 · TanStack/table

KevinVandy · 2026-08-25T21:43:48Z

🎯 Changes

Fixes #6551. Supersedes #6552 while retaining Lazizbek Ergashev's contribution via co-author credit.

Emit grouped flatRows in parent-first preorder for flat and hierarchical data without adding another grouping traversal.
Preserve parent-first ordering in grouped worker reconstruction.
Deduplicate expanded worker reconstruction and rebuild its flatRows from the completed tree, fixing an additional downstream ordering failure found during the pipeline audit.
Add exact grouped and worker round-trip regressions plus one invariant test covering core, filtered, grouped, sorted, expanded, and paginated row models.

Performance and bundle impact: the synchronous grouping path remains O(rows) and uses its existing recursive pass; synthetic groups reserve their output slot before descendants are built. Expanded worker reconstruction adds one O(rows) traversal and a temporary Set only when rebuilding an expanded tree payload, replacing duplicated output entries with one parent-first entry per row. The production change is small and introduces no dependency or public API changes.

Validation:

pnpm test — 871 tasks passed
pnpm test:e2e — 407 tasks passed after the repository retry runner resolved nine flaky example tasks
pnpm --filter @tanstack/table-core test:types
focused row-model tests — 29 passed
ESLint, Prettier, and git diff --check

✅ Checklist

I have followed the steps in the Contributing guide.
I have tested code changes locally with pnpm test and pnpm test:e2e, or these tests do not apply to this pull request.
I fully understand the code in this pull request, including any code generated with AI assistance.

🚀 Release Impact

This change affects published code, and I have generated a changeset.
This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

Bug Fixes
- Corrected flattened row ordering so grouped rows consistently appear before their descendants.
- Preserved row identity and removed duplicate entries across filtering, sorting, expansion, pagination, and worker processing.
- Improved consistency when rebuilding and serializing hierarchical row data.
Tests
- Added coverage for preorder flattening and expanded grouped data across row-model stages.
Documentation
- Updated performance notes to reflect the corrected row-ordering behavior.

Co-authored-by: Lazizbek Ergashev <lazerg2@gmail.com>

coderabbitai · 2026-08-25T21:44:43Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Run ID: 966b0a38-f312-4964-97a9-38a0da8371b5

📥 Commits

Reviewing files that changed from the base of the PR and between 468f267 and 4df2ce9.

📒 Files selected for processing (7)

.changeset/tidy-groups-walk.md
packages/table-core/src/features/column-grouping/createGroupedRowModel.ts
packages/table-core/src/worker/rebuildRowModel.ts
packages/table-core/tests/implementation/core/row-models/rowModelFlatRowsOrder.test.ts
packages/table-core/tests/implementation/features/column-grouping/createGroupedRowModel.test.ts
packages/table-core/tests/unit/worker/serializeRebuild.test.ts
perf-new.md

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📝 Walkthrough

Walkthrough

Grouped and worker row models now emit flatRows in parent-before-descendant order. Expanded worker rebuilds reconstruct preorder rows and remove duplicate IDs. Tests cover grouped trees, pipeline stages, and serialization round trips.

Changes

Flat row ordering

Layer / File(s)	Summary
Grouped row preorder flattening `packages/table-core/src/features/column-grouping/createGroupedRowModel.ts`, `packages/table-core/tests/implementation/features/column-grouping/createGroupedRowModel.test.ts`, `packages/table-core/tests/implementation/core/row-models/rowModelFlatRowsOrder.test.ts`	Grouped traversal reserves each group position before descendants. Tests verify preorder ordering and unique IDs across row-model stages.
Worker preorder reconstruction `packages/table-core/src/worker/rebuildRowModel.ts`, `packages/table-core/tests/unit/worker/serializeRebuild.test.ts`, `.changeset/tidy-groups-walk.md`, `perf-new.md`	Worker rebuilds flatten grouped and expanded trees in preorder. Serialization tests verify row identity and ordering. Changeset and performance notes document the correction.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 4df2c

The change preserves parent-first row ordering across grouped and worker-backed models with focused regression coverage; no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 5 files. (2 skipped: 2 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: preserving preorder for grouped flatRows.
Description check	✅ Passed	The description is complete. It explains the changes, motivation, performance impact, validation results, checklist status, and release impact. It also includes the required changeset information.
Linked Issues check	✅ Passed	The implementation addresses issue `#6551` by emitting grouped flatRows in parent-first preorder for flat and hierarchical data. It also preserves ordering through worker reconstruction and expanded or …
Out of Scope Changes check	✅ Passed	The changes are within scope. Production changes, worker reconstruction updates, tests, the changeset, and performance documentation all support the stated grouped flatRows ordering objectives.

Full details: Linked Issues check

Explanation

The implementation addresses issue #6551 by emitting grouped flatRows in parent-first preorder for flat and hierarchical data. It also preserves ordering through worker reconstruction and expanded or paginated pipelines, with regression coverage.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 5 files. (2 skipped: 2 unsupported.)

✨ Finishing Touches 💡 1

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Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch fix/grouped-row-model-preorder-flatrows

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github-actions · 2026-08-25T21:49:09Z

🚀 Changeset Version Preview

1 package(s) bumped directly, 11 bumped as dependents.

🟩 Patch bumps

Package	Version	Reason
`@tanstack/table-core`	9.2.2 → 9.2.3	Changeset
`@tanstack/alpine-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/angular-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/angular-table-devtools`	9.2.2 → 9.2.3	Dependent
`@tanstack/ember-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/lit-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/octane-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/preact-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/react-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/solid-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/svelte-table`	9.2.2 → 9.2.3	Dependent
`@tanstack/vue-table`	9.2.2 → 9.2.3	Dependent

nx-cloud · 2026-08-25T21:49:38Z

View your CI Pipeline Execution ↗ for commit 4df2ce9

Command	Status	Duration	Result
`nx affected --targets=test:eslint,test:sherif,t...`	✅ Succeeded	8m 54s	View ↗
`nx run-many --targets=build --exclude=examples/**`	✅ Succeeded	1m	View ↗

☁️ Nx Cloud last updated this comment at 2026-08-25 21:59:26 UTC

pkg-pr-new · 2026-08-25T21:52:03Z

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commit: 4df2ce9

fix(table-core): preserve grouped flat row preorder

4df2ce9

Co-authored-by: Lazizbek Ergashev <lazerg2@gmail.com>

KevinVandy merged commit 3b94648 into main Aug 25, 2026
10 checks passed

KevinVandy deleted the fix/grouped-row-model-preorder-flatrows branch August 25, 2026 22:01

github-actions Bot mentioned this pull request Aug 25, 2026

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fix(table-core): preserve grouped flatRows preorder - #6576

fix(table-core): preserve grouped flatRows preorder#6576
KevinVandy merged 1 commit into
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fix/grouped-row-model-preorder-flatrows

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