fix(table): prevent crash when pressing Enter in a table cell

[y-temp4]

Summary

Fixes a crash where pressing Enter inside a table cell throws TransformError: Cannot join tableCell onto blockContainer and leaves the editor in an unrecoverable state.

Closes #2792.

Symptom & minimal reproduction

Reproducible on the official demo (no app-specific code needed): https://www.blocknotejs.org/demo#pwls9

1. Open the demo (it contains a table).
2. Click inside a cell in the last row.
3. Press Enter → the editor crashes.

It also reproduces by:

• selecting text within a last-row cell and pressing Enter;
• selecting across multiple cells (a CellSelection) and pressing Enter.

Stack trace

TransformError: Cannot join tableCell onto blockContainer
  at new TransformError (prosemirror-transform)
  at Transaction.step (prosemirror-transform)
  at split (prosemirror-transform)
  at Transaction.split (prosemirror-transform)
  at splitBlockTr (packages/core/src/api/blockManipulation/commands/splitBlock/splitBlock.ts:55)  // tr.split(posInBlock, 2, types)
  at splitBlockCommand (.../splitBlock.ts:22)
  at KeyboardShortcutsExtension Enter handler (.../KeyboardShortcuts/KeyboardShortcutsExtension.ts:918)
      // chain().deleteSelection().command(splitBlockCommand(...)).run() — reached because the
      // table's Enter handler returned false and fell through to the default splitBlock

Cause

The table-specific Enter handler in packages/core/src/blocks/Table/TableExtension.ts (added in #2685, "feat: Enter moves selection to cell below in tables (BLO-1006)") only handles the case where a cell exists below the cursor. In several edge cases it returns false and falls through to the default splitBlock handler.

splitBlockTr resolves the nearest block container of a cell to the outer blockContainer that wraps the whole table (whose content — the table — is non-empty, so the "empty block" early-outs don't apply), and then calls tr.split(pos, 2, ...) at a position deep inside the cell. Splitting a tableCell at depth 2 is invalid, so ProseMirror throws Cannot join tableCell onto blockContainer.

Edge cases that triggered the fallback (and therefore the crash):

1. Cursor in a cell on the last row (no cell below → !$nextCell → false).
2. A non-empty text selection inside a last-row cell.
3. A multi-cell selection (CellSelection) — the selection head resolves to a tableRow, so the handler's previous $head.parent.type.name === "tableParagraph" guard was bypassed entirely.

Fix

• Detect being inside a table with isInTable instead of checking that the cursor's parent is a tableParagraph. This also covers multi-cell selections, where the head resolves to a tableRow.
• Move the selection to the cell below when there is one (existing behavior preserved).
• Always consume the Enter key while inside a table, so it never falls through to the default splitBlock handler. On the last row, Enter is now a no-op.

Affected versions

@blocknote/core 0.51.2 and 0.51.3 (latest). The regression was introduced in 0.50.0 by #2685.

Tests

Adds packages/core/src/blocks/Table/TableExtension.test.ts with regression tests that:

• confirm Enter still moves the selection to the cell below;
• confirm Enter on the last row no longer crashes and is a no-op (table structure intact);
• confirm a non-empty text selection in the last row no longer crashes;
• confirm a multi-cell CellSelection no longer crashes.

All @blocknote/core tests pass (449 passed / 3 skipped), and lint + build (tsc) succeed.

Summary by CodeRabbit

• Bug Fixes

  • Enter now consistently moves focus to the cell below when inside tables and consumes the Enter key to avoid unexpected behavior.
  • Pressing Enter on the last row (cursor, text selection, or multi-cell selection) no longer alters the document or causes issues.

• Tests

  • Added tests covering Enter behavior across table positions and selection types.

[vercel]

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a6ce08ca-7cd9-4871-a9ba-52484e8f7a07

📥 Commits

Reviewing files that changed from the base of the PR and between b4af8bb and c484155.

📒 Files selected for processing (2)

• packages/core/src/blocks/Table/TableExtension.test.ts
• packages/core/src/blocks/Table/TableExtension.ts

💤 Files with no reviewable changes (2)

• packages/core/src/blocks/Table/TableExtension.test.ts
• packages/core/src/blocks/Table/TableExtension.ts

---

📝 Walkthrough

Walkthrough

Refactors table Enter handling to always consume Enter inside tables and safely handle missing below-cells; adds Vitest tests that simulate Enter and verify selection moves for middle rows and no-op safe behavior for last-row cursor, text selections, and multi-cell selections.

Changes

Table Enter Key Behavior Fix

Layer / File(s)	Summary
Enter handler fix packages/core/src/blocks/Table/TableExtension.ts	Gates Enter handling with isInTable, safely finds current/next cell using selectionCell/nextCell, moves selection to the cell below only when present, and always returns true to consume Enter inside tables.
Test suite for Enter behavior packages/core/src/blocks/Table/TableExtension.test.ts	Adds a Vitest/jsdom test module with pressEnter helper, a static test table, utilities to locate and set cursor/selection in cells, and tests that validate moving selection from middle rows and safe no-op behavior on last-row cursor, non-empty text selection, and multi-cell selection.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• TypeCellOS/BlockNote#2685: Prior implementation of Enter key behavior to move selection to the cell below in tables, which this PR refines and covers with tests.

Suggested reviewers

• matthewlipski
• nperez0111

Poem

🐰 In rows of cells I softly tread,
Press Enter wide — no crash, no dread.
From middle jump to the row beneath,
Last-row presses keep the doc complete.
Hooray — the table stays well-fed! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title clearly and concisely summarizes the main change: fixing a crash when pressing Enter in a table cell, which is the core objective of the PR.
Description check	✅ Passed	The PR description is comprehensive and well-structured, covering the issue, root cause, fix approach, testing, and affected versions. It addresses the key sections with sufficient detail.
Linked Issues check	✅ Passed	The code changes fully implement the fix described in issue #2792: using isInTable to detect table context, moving selection to cell below when available, and always consuming Enter to prevent falling through to splitBlock.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the table Enter key crash: modified TableExtension.ts to fix the handler logic and added comprehensive regression tests in TableExtension.test.ts.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[nperez0111]

This looks right to me, the AI generated comments are annoying though, they are not saying anything useful to someone reading the code now

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commit: b4af8bb

[y-temp4]

Thanks for the review. I removed the redundant generated comments and kept only the required Vitest environment annotation.