From 88cc87130c8b3d9a32e1d9f22ba69b022d53d238 Mon Sep 17 00:00:00 2001
From: "YUKI \"Piro\" Hiroshi" <piro.outsider.reflex@gmail.com>
Date: Thu, 5 Nov 2020 04:01:38 +0900
Subject: [PATCH] Move tabs across windows with their tree structure more
 safely #2546

---
 webextensions/background/api-tabs-listener.js | 6 +++++-
 webextensions/background/handle-new-tabs.js   | 8 ++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/webextensions/background/api-tabs-listener.js b/webextensions/background/api-tabs-listener.js
index 113589099..797a21109 100644
--- a/webextensions/background/api-tabs-listener.js
+++ b/webextensions/background/api-tabs-listener.js
@@ -974,12 +974,16 @@ async function onDetached(tabId, detachInfo) {
     if (byInternalOperation)
       oldWindow.toBeDetachedTabs.delete(tabId);
 
+    const descendants = oldTab.$TST.descendants;
     const info = {
       ...detachInfo,
       byInternalOperation,
       windowId:    detachInfo.oldWindowId,
-      descendants: oldTab.$TST.descendants
+      structure:   TreeBehavior.getTreeStructureFromTabs([oldTab, ...descendants]),
+      descendants
     };
+    const alreadyMovedAcrossWindows = Array.from(mTreeInfoForTabsMovingAcrossWindows.values(), info => info.descendants.map(tab => tab.id)).some(tabIds => tabIds.includes(tabId));
+    if (!alreadyMovedAcrossWindows)
     mTreeInfoForTabsMovingAcrossWindows.set(tabId, info);
 
     if (!byInternalOperation) // we should process only tabs detached by others.
diff --git a/webextensions/background/handle-new-tabs.js b/webextensions/background/handle-new-tabs.js
index f713c2d53..d4873c30a 100644
--- a/webextensions/background/handle-new-tabs.js
+++ b/webextensions/background/handle-new-tabs.js
@@ -369,10 +369,18 @@ Tab.onAttached.addListener(async (tab, info = {}) => {
     insertAfter:         tab
   });
   log('moved descendants: ', () => movedTabs.map(dumpTab));
+  if (info.descendants.length == movedTabs.length) {
+    await Tree.applyTreeStructureToTabs(
+      [tab, ...movedTabs],
+      info.structure
+    );
+  }
+  else {
   for (const movedTab of movedTabs) {
     Tree.attachTabTo(movedTab, tab, {
       broadcast: true,
       dontMove:  true
     });
   }
+  }
 });