fix: preserve multiline content when pasting TSV data

- Add parseTsv to handle multiline cells instead of splitting every newline
- Auto-detect column count from clipboard when grid has more columns
- Add countTabs helper, optimize with single-pass parsing

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: sadmann7

src/hooks/test/use-data-grid.test.tsx

@@ -1033,6 +1033,51 @@ describe("useDataGrid", () => {
         ]),
       );
     });
+
+    it("should preserve multiline content within cells when pasting", async () => {
+      const onPaste = vi.fn().mockResolvedValue(undefined);
+      mockClipboard.readText.mockResolvedValue(
+        "Alice\tKickflip\t95\nBob\tTrick with\nmultiple\nlines\t98",
+      );
+
+      const { result } = renderHook(
+        () =>
+          useDataGrid({
+            data: testData,
+            columns: testColumns,
+            onPaste,
+          }),
+        { wrapper: createWrapper() },
+      );
+
+      act(() => {
+        result.current.tableMeta.onCellClick?.(0, "name");
+      });
+
+      await act(async () => {
+        await result.current.tableMeta.onCellsPaste?.();
+      });
+
+      expect(onPaste).toHaveBeenCalledWith(
+        expect.arrayContaining([
+          expect.objectContaining({
+            rowIndex: 0,
+            columnId: "score",
+            value: 95,
+          }),
+          expect.objectContaining({
+            rowIndex: 1,
+            columnId: "trick",
+            value: "Trick with\nmultiple\nlines",
+          }),
+          expect.objectContaining({
+            rowIndex: 1,
+            columnId: "score",
+            value: 98,
+          }),
+        ]),
+      );
+    });
   });
 
   describe("cut operations", () => {

src/hooks/use-data-grid.ts

@@ -30,6 +30,7 @@ import {
   getScrollDirection,
   matchSelectOption,
   parseCellKey,
+  parseTsv,
   scrollCellIntoView,
 } from "@/lib/data-grid";
 import type {
@@ -699,10 +700,7 @@ function useDataGrid<TData>({
           if (!clipboardText) return;
         }
 
-        const pastedRows = clipboardText
-          .split("\n")
-          .filter((row) => row.length > 0);
-        const pastedData = pastedRows.map((row) => row.split("\t"));
+        const pastedData = parseTsv(clipboardText, navigableColumnIds.length);
 
         const startRowIndex = currentState.focusedCell.rowIndex;
         const startColIndex = navigableColumnIds.indexOf(

src/lib/data-grid.ts

@@ -256,6 +256,53 @@ export function scrollCellIntoView<TData>(params: {
   container.scrollLeft += scrollDelta;
 }
 
+function countTabs(s: string): number {
+  let n = 0;
+  for (let i = 0; i < s.length; i++) if (s[i] === "\t") n++;
+  return n;
+}
+
+export function parseTsv(
+  text: string,
+  fallbackColumnCount: number,
+): string[][] {
+  const lines = text.split("\n");
+  let maxTabs = 0;
+  for (const line of lines) {
+    const n = countTabs(line);
+    if (n > maxTabs) maxTabs = n;
+  }
+  const cols = maxTabs > 0 ? maxTabs + 1 : fallbackColumnCount;
+  if (cols <= 0) return [];
+
+  const rows: string[][] = [];
+  let buf = "";
+
+  for (const line of lines) {
+    const tc = countTabs(line);
+
+    if (tc === cols - 1) {
+      if (buf && countTabs(buf) === cols - 1) rows.push(buf.split("\t"));
+      buf = "";
+      rows.push(line.split("\t"));
+    } else if (tc === 0 && rows.length > 0 && !buf) {
+      const last = rows[rows.length - 1];
+      if (last) {
+        const cell = last[cols - 1];
+        if (cell !== undefined) last[cols - 1] = `${cell}\n${line}`;
+      }
+    } else {
+      buf = buf ? `${buf}\n${line}` : line;
+    }
+  }
+
+  if (buf && countTabs(buf) === cols - 1) rows.push(buf.split("\t"));
+
+  return rows.length > 0
+    ? rows
+    : lines.filter((l) => l.length > 0).map((l) => l.split("\t"));
+}
+
 export function getIsInPopover(element: unknown): boolean {
   if (!(element instanceof Element)) return false;