Bug 1962592 - Reduce tab moves in adoptTabGroup r=tabbrowser-reviewers,dao

Differential Revision: https://phabricator.services.mozilla.com/D246702

browser/components/extensions/test/browser/browser_ext_tabGroups_move_event_order.js

@@ -86,3 +86,90 @@ add_task(async function tabGroups_move_to_other_window() {
   await extension.awaitMessage("done");
   await extension.unload();
 });
+
+add_task(async function tabGroups_move_multiple_tabs_to_other_window() {
+  let extension = ExtensionTestUtils.loadExtension({
+    manifest: {
+      permissions: ["tabGroups"],
+    },
+    async background() {
+      // Setup: The tabs that we are going to group.
+      const tabs = [
+        await browser.tabs.create({}),
+        await browser.tabs.create({}),
+      ];
+      const oldWinId = tabs[0].windowId;
+      const tabIds = tabs.map(t => t.id);
+      browser.test.log(`Tab ID: ${tabIds}, old win ID: ${oldWinId}`);
+      const groupId = await browser.tabs.group({ tabIds });
+      // Setup: Create window with two tabs.
+      const { id: windowId } = await browser.windows.create({});
+      const tab2 = await browser.tabs.create({ windowId });
+      browser.test.assertEq(1, tab2.index, `Two tabs in window ${windowId}`);
+
+      const events = [];
+      browser.tabGroups.onCreated.addListener(group => {
+        browser.test.fail(`Unexpected tabGroups.onCreated: ${group.id}`);
+      });
+      browser.tabGroups.onRemoved.addListener(group => {
+        browser.test.fail(`Unexpected tabGroups.onRemoved: ${group.id}`);
+      });
+      browser.tabGroups.onMoved.addListener(group => {
+        browser.test.assertEq(groupId, group.id, "onMoved fired for group");
+        events.push("tabGroups.onMoved");
+      });
+      browser.tabs.onMoved.addListener((movedTabId, moveInfo) => {
+        // onDetached & onAttached should fire when moving to another window.
+        browser.test.fail(
+          `Unexpected tabs.onMoved: ${JSON.stringify(moveInfo)}`
+        );
+      });
+      browser.tabs.onDetached.addListener((movedTabId, detachInfo) => {
+        browser.test.assertEq(oldWinId, detachInfo.oldWindowId, "oldWindowId");
+        events.push(`tabs.onDetached:${detachInfo.oldPosition}:${movedTabId}`);
+      });
+      browser.tabs.onAttached.addListener((movedTabId, attachInfo) => {
+        browser.test.assertEq(windowId, attachInfo.newWindowId, "newWindowId");
+        events.push(`tabs.onAttached:${attachInfo.newPosition}:${movedTabId}`);
+      });
+
+      browser.test.assertDeepEq([], events, "No tabGroups event yet");
+      // Move tab group to start of tab strip.
+      const moved = await browser.tabGroups.move(groupId, {
+        windowId,
+        index: 0,
+      });
+      browser.test.assertEq(groupId, moved.id, "Group ID did not change");
+      browser.test.assertEq(windowId, moved.windowId, "Group moved to window");
+
+      browser.test.assertEq(
+        0,
+        (await browser.tabs.get(tabIds[0])).index,
+        `First tab appears at the expected index`
+      );
+      browser.test.assertEq(
+        1,
+        (await browser.tabs.get(tabIds[1])).index,
+        `Second tab appears at the expected index`
+      );
+
+      await browser.windows.remove(windowId);
+      browser.test.assertDeepEq(
+        [
+          `tabs.onDetached:1:${tabIds[0]}`,
+          `tabs.onAttached:0:${tabIds[0]}`,
+          `tabs.onDetached:1:${tabIds[1]}`,
+          `tabs.onAttached:1:${tabIds[1]}`,
+          "tabGroups.onMoved",
+        ],
+        events,
+        "Expected events when moving tab group (2 tabs) to a new window"
+      );
+
+      browser.test.sendMessage("done");
+    },
+  });
+  await extension.startup();
+  await extension.awaitMessage("done");
+  await extension.unload();
+});

browser/components/tabbrowser/content/tabbrowser.js

@@ -3155,6 +3155,7 @@
       let newTabs = [];
       for (let tab of group.tabs) {
         newTabs.push(this.adoptTab(tab, { elementIndex }));
+        ++elementIndex;
       }
 
       return this.addTabGroup(newTabs, {