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Table adjacent-cell queries must resolve visual neighbors

docs/solutions/logic-errors/2026-03-30-table-adjacent-cell-queries-must-resolve-visual-neighbors.md

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Table adjacent-cell queries must resolve visual neighbors

Problem

Table border toggles broke once merged cells changed the visual grid.

Selecting a cell below a colSpan merge and toggling its top border wrote to the wrong cell in the row above, because the helper treated "cell above" as "same sibling index in the previous row."

What Didn't Work

  • Raw path math like PathApi.previous(...) and [row - 1, cellIndex]
  • Assuming table child order still matched visual column positions after merges

Solution

Move adjacent-cell ownership into a shared query helper that resolves neighbors by visual table coordinates, not raw sibling position.

getAdjacentTableCell(...) now:

  • resolves the current cell, row, and table with getTableEntries(...)
  • reads the current visual row and column with getCellIndices(...)
  • finds the real adjacent cell with findCellByIndexes(...)
  • reconstructs the actual Slate path with getCellPath(...)

getTopTableCell(...) and getLeftTableCell(...) both delegate to that helper.

Why This Works

Merged cells split visual position from tree sibling position.

Once a cell spans extra columns or rows, the neighbor you want is "the cell covering visual row X / col Y," not "the previous sibling" or "the child at the same index in another row."

findCellByIndexes(...) already understands spans, so reusing it at the query seam fixes border toggles without teaching every caller how merged layouts work.

Verification

These checks passed:

bash
pnpm --filter @platejs/table test packages/table/src/lib/queries/getTopTableCell.spec.tsx packages/table/src/lib/queries/getSelectedCellsBorders.spec.tsx packages/table/src/react/components/TableCellElement/setSelectedCellsBorder.integration.spec.tsx packages/table/src/react/components/TableCellElement/setSelectedCellsBorder.spec.tsx
pnpm install
pnpm turbo build --filter=./packages/table
pnpm turbo typecheck --filter=./packages/table
pnpm lint:fix

The new coverage proves both layers:

  • getTopTableCell.spec.tsx proves merged columns resolve the spanning cell above
  • setSelectedCellsBorder.integration.spec.tsx proves the top-border toggle updates the spanning neighbor instead of the wrong sibling

Prevention

  • Table neighbor helpers must resolve visual coordinates, not sibling indexes
  • When merges are involved, keep one seam-level helper spec and one user-flow integration spec
  • If a caller wants "adjacent cell," fix the query helper first instead of patching each transform
  • #4111
  • .claude/docs/solutions/logic-errors/2026-03-29-table-border-toggle-must-clear-active-cell-selection-before-adjacent-cell-writes.md