pivot: e2e test for expansion surviving add-measure and sort

Adds a Playwright test asserting that expanding a nested row and then
adding a measure or sorting keeps the row expanded (#9781).

Author: mahdi13

web-local/tests/explores/pivot.spec.ts

@@ -700,3 +700,66 @@ test.describe("pivot run through", () => {
     await validateTableContents(page, "table", expectSortedDeltaCol, 4);
   });
 });
+
+test.describe("pivot expansion persistence", () => {
+  test.use({ project: "AdBids" });
+
+  // Expanded rows are keyed by dimension values, so they survive config
+  // changes that keep the same rows. Previously any change reset the tree.
+  // https://github.com/rilldata/rill/issues/9781
+  test("expanded rows survive adding a measure and sorting", async ({
+    page,
+  }) => {
+    test.setTimeout(45_000);
+    const watcher = new ResourceWatcher(page);
+
+    await gotoNavEntry(page, "/metrics/AdBids_metrics.yaml");
+    await page.getByRole("button", { name: "switch to code editor" }).click();
+    await watcher.updateAndWaitForDashboard(pivotDashboard);
+    await gotoNavEntry(page, "/dashboards/AdBids_metrics_explore.yaml");
+    await page.getByRole("button", { name: "Preview" }).click();
+    await page.getByRole("link", { name: "Pivot", exact: true }).click();
+
+    const rowZone = page.locator(".dnd-zone.horizontal").nth(0);
+    const columnZone = page.locator(".dnd-zone.horizontal").nth(1);
+    const totalRecords = page.getByLabel("Total records pivot chip", {
+      exact: true,
+    });
+    const bidPrice = page.getByLabel("Sum of Bid Price pivot chip", {
+      exact: true,
+    });
+    const timeMonth = page.getByLabel("Time pivot chip", { exact: true });
+    const publisher = page.getByLabel("Publisher pivot chip", { exact: true });
+
+    // Build rows = Time (month) > Publisher, columns = Total records.
+    await dragPivotChip(page, totalRecords, columnZone);
+    await dragPivotChip(page, timeMonth, rowZone);
+    await dragPivotChip(page, publisher, rowZone);
+    await expect(page.locator(".status.running")).toHaveCount(0);
+
+    // Expand a month; a nested publisher row becomes visible.
+    await page.locator("td").filter({ hasText: "Jan" }).first().click();
+    await expect(page.locator(".status.running")).toHaveCount(0);
+    await expect(
+      page.locator("td").filter({ hasText: "Facebook" }).first(),
+    ).toBeVisible();
+
+    // Adding a measure used to collapse the tree; the nested row must remain.
+    await dragPivotChip(page, bidPrice, columnZone);
+    await expect(page.locator(".status.running")).toHaveCount(0);
+    await expect(
+      page.locator("td").filter({ hasText: "Facebook" }).first(),
+    ).toBeVisible();
+
+    // Sorting by a measure used to collapse the tree; still expanded.
+    await page
+      .locator(".header-cell")
+      .filter({ hasText: "Total records" })
+      .first()
+      .click();
+    await expect(page.locator(".status.running")).toHaveCount(0);
+    await expect(
+      page.locator("td").filter({ hasText: "Facebook" }).first(),
+    ).toBeVisible();
+  });
+});