fix(table): collapsed cell-border rendering with tblPrEx and gridAfter

Render w:tblPrEx row-level borders (merged per edge over the table borders) and resolve collapsed shared edges with single-owner ownership plus the §17.4.66 winner, so adjacent cell borders draw exactly once (no doubling) and asymmetric or borderless edges keep their line (no drop). Handle trailing w:gridAfter columns: the rightmost real cell owns the right border, the resize overlay skips the degenerate spacer, and a cell spanning past the next row's coverage owns its full-width bottom while that row suppresses its top. (SD-3345, SD-2969)

Author: tupizz

packages/layout-engine/contracts/src/index.ts

@@ -760,6 +760,14 @@ export type TableRowAttrs = {
     value: number;
     rule?: 'auto' | 'atLeast' | 'exact' | string;
   };
+  /**
+   * Row-level border override from OOXML `w:tblPrEx/w:tblBorders` (§17.4.61).
+   * Table property exceptions override the table-level borders for this row
+   * only. Rows without a `tblPrEx` border block leave this undefined and fall
+   * through to the table's borders. Resolved (eighth-points → px) by the v1
+   * layout-adapter; the painter merges it over the table borders per edge.
+   */
+  borders?: TableBorders;
 };
 
 export type TableRow = {

packages/layout-engine/painters/dom/src/table/renderTableFragment.test.ts

@@ -577,6 +577,61 @@ describe('renderTableFragment', () => {
       });
     });
 
+    // Build a one-row measure whose single cell occupies only column 0, leaving
+    // the last grid column as an empty trailing gridAfter spacer.
+    const spacerMeasure = (spacerWidth: number): TableMeasure => ({
+      kind: 'table',
+      rows: [
+        {
+          cells: [
+            {
+              paragraph: { kind: 'paragraph', lines: [], totalHeight: 20 },
+              width: 100,
+              height: 20,
+              gridColumnStart: 0,
+              colSpan: 1,
+            },
+          ],
+          height: 20,
+        },
+      ],
+      columnWidths: [100, spacerWidth],
+      totalWidth: 100 + spacerWidth,
+      totalHeight: 20,
+    });
+
+    const renderSpacerTable = (spacerWidth: number): Element =>
+      renderTableFragment({
+        doc,
+        fragment: createTestTableFragment([
+          { index: 0, x: 0, width: 100, minWidth: 25, resizable: true },
+          { index: 1, x: 100, width: spacerWidth, minWidth: 25, resizable: true },
+        ]),
+        context,
+        block: createTestTableBlock(),
+        measure: spacerMeasure(spacerWidth),
+        cellSpacingPx: 0,
+        effectiveColumnWidths: [100, spacerWidth],
+        renderLine: () => doc.createElement('div'),
+        applyFragmentFrame: () => {},
+        applySdtDataset: () => {},
+        applyStyles: () => {},
+      });
+
+    it('omits the resize boundary for a degenerate trailing gridAfter spacer column (SD-3345)', () => {
+      // Spacer is narrower than its own min width → degenerate → its left-edge
+      // resize boundary is suppressed so it does not crowd the table-edge handle.
+      const parsed = JSON.parse(renderSpacerTable(7).getAttribute('data-table-boundaries')!);
+      expect(parsed.segments[1]).toEqual([]);
+    });
+
+    it('keeps the resize boundary for a normal-width trailing column (control)', () => {
+      // Same shape but the trailing column meets its min width → not degenerate →
+      // the boundary is kept. Proves the suppression is gated on degeneracy.
+      const parsed = JSON.parse(renderSpacerTable(40).getAttribute('data-table-boundaries')!);
+      expect(parsed.segments[1].length).toBeGreaterThan(0);
+    });
+
     it('should embed row boundary metadata when rowBoundaries are present', () => {
       const block = createTestTableBlock();
       const measure = createTestTableMeasure();

packages/layout-engine/painters/dom/src/table/renderTableFragment.ts

@@ -313,6 +313,28 @@ export const renderTableFragment = (deps: TableRenderDependencies): HTMLElement
       // Track which column boundaries exist in this row
       const boundariesInRow = new Set<number>();
 
+      // Columns occupied by a cell in this row. Used to detect a trailing
+      // w:gridAfter spacer column this row leaves empty.
+      const occupiedCols = new Set<number>();
+      for (const cellMeasure of rowMeasure.cells) {
+        const s = cellMeasure.gridColumnStart ?? 0;
+        const sp = cellMeasure.colSpan ?? 1;
+        for (let c = s; c < s + sp; c++) occupiedCols.add(c);
+      }
+      // A degenerate trailing gridAfter spacer (last column, unoccupied this row,
+      // narrower than its own min width) sits a few px from the table edge. Emitting
+      // a resize boundary at its left edge crowds the table-edge handle and reads as a
+      // doubled border on hover, so skip that boundary for this row (SD-3345).
+      const lastColIndex = columnCount - 1;
+      const lastColMeta = fragment.metadata.columnBoundaries[lastColIndex];
+      const skipTrailingSpacerBoundary =
+        lastColIndex > 0 &&
+        !occupiedCols.has(lastColIndex) &&
+        !!lastColMeta &&
+        typeof lastColMeta.width === 'number' &&
+        typeof lastColMeta.minWidth === 'number' &&
+        lastColMeta.width < lastColMeta.minWidth;
+
       for (const cellMeasure of rowMeasure.cells) {
         const startCol = cellMeasure.gridColumnStart ?? 0;
         const colSpan = cellMeasure.colSpan ?? 1;
@@ -323,8 +345,10 @@ export const renderTableFragment = (deps: TableRenderDependencies): HTMLElement
         if (startCol > 0) {
           boundariesInRow.add(startCol);
         }
-        // End boundary (right edge of cell)
-        if (endCol < columnCount) {
+        // End boundary (right edge of cell), unless it lands on a degenerate
+        // trailing gridAfter spacer (its left edge is the table edge for practical
+        // purposes, handled by the table-edge handle).
+        if (endCol < columnCount && !(skipTrailingSpacerBoundary && endCol === lastColIndex)) {
           boundariesInRow.add(endCol);
         }
       }
@@ -428,6 +452,9 @@ export const renderTableFragment = (deps: TableRenderDependencies): HTMLElement
         y,
         rowMeasure,
         row: block.rows[r],
+        prevRow: r > 0 ? block.rows[r - 1] : undefined,
+        prevRowMeasure: r > 0 ? measure.rows[r - 1] : undefined,
+        nextRowMeasure: r < block.rows.length - 1 ? measure.rows[r + 1] : undefined,
         totalRows: block.rows.length,
         tableBorders,
         columnWidths: effectiveColumnWidths,
@@ -595,6 +622,9 @@ export const renderTableFragment = (deps: TableRenderDependencies): HTMLElement
       y,
       rowMeasure,
       row: block.rows[r],
+      prevRow: r > 0 ? block.rows[r - 1] : undefined,
+      prevRowMeasure: r > 0 ? measure.rows[r - 1] : undefined,
+      nextRowMeasure: r < block.rows.length - 1 ? measure.rows[r + 1] : undefined,
       totalRows: block.rows.length,
       tableBorders,
       columnWidths: effectiveColumnWidths,