[lexical-table] Bug Fix: include first cell contents in partial backwards table selection (#7998)

Author: patrick-atticus

packages/lexical-playground/__tests__/e2e/Selection.spec.mjs

@@ -1499,7 +1499,7 @@ test.describe.parallel('Selection', () => {
     await assertSelection(page, {
       anchorOffset: 0,
       anchorPath: [2],
-      focusOffset: 1,
+      focusOffset: 0,
       focusPath: [1, 1, 0],
     });
   });
@@ -1544,7 +1544,7 @@ test.describe.parallel('Selection', () => {
       await assertSelection(page, {
         anchorOffset: 0,
         anchorPath: [1],
-        focusOffset: 1,
+        focusOffset: 0,
         focusPath: [0, 1, 0],
       });
     },
@@ -1659,7 +1659,7 @@ test.describe.parallel('Selection', () => {
     await assertSelection(page, {
       anchorOffset: 0,
       anchorPath: [2],
-      focusOffset: 1,
+      focusOffset: 0,
       focusPath: [1, 1, 0],
     });
   });

packages/lexical-table/src/LexicalTableSelectionHelpers.ts

@@ -1045,11 +1045,11 @@ export function applyTableHandlers(
               );
               const firstCell = tableMap[0][0].cell;
               const lastCell = tableMap[tableMap.length - 1].at(-1)!.cell;
+              // When backward, focus should be at START of first cell (0)
+              // When forward, focus should be at END of last cell (getChildrenSize)
               newSelection.focus.set(
                 isBackward ? firstCell.getKey() : lastCell.getKey(),
-                isBackward
-                  ? firstCell.getChildrenSize()
-                  : lastCell.getChildrenSize(),
+                isBackward ? 0 : lastCell.getChildrenSize(),
                 'element',
               );
             } else if (isAnchorInside) {