Bug 1641345 - Relationship among <browser>, tabmail tab, and web-ext tabId is broken for shared messagepane tabs. r=darktrojan

mail/base/content/tabmail.js

@@ -468,6 +468,10 @@
        * open when we received the call to openTab.
        */
       this._mostRecentTabInfo = null;
+      /**
+       * Tab id, incremented on each openTab() and set on the browser.
+       */
+      this.tabId = 0;
       this.tabTypes = {};
       this.tabModes = {};
       this.defaultTabMode = null;
@@ -860,12 +864,20 @@
           },
         };
 
+        firstTab.tabNode = this.tabContainer.arrowScrollbox.firstElementChild;
+        firstTab.tabId = this.tabId++;
+
         firstTab.mode.tabs.push(firstTab);
         this.tabInfo[0] = this.currentTabInfo = firstTab;
         let tabOpenFirstFunc =
           firstTab.mode.openFirstTab || firstTab.mode.tabType.openFirstTab;
         tabOpenFirstFunc.call(firstTab.mode.tabType, firstTab);
         this.setTabTitle(null);
+
+        // Set the tabId after defining a <browser> and before notifications.
+        firstTab.browser = this.getBrowserForTab(firstTab);
+        firstTab.browser._activeTabId = firstTab.tabId;
+
         for (let tabMonitor of this.tabMonitors) {
           if ("onTabOpened" in tabMonitor) {
             tabMonitor.onTabOpened(firstTab, true);
@@ -934,6 +946,7 @@
           _ext: {},
         };
 
+        tab.tabId = this.tabId++;
         tabMode.tabs.push(tab);
         var t = document.createXULElement("tab", { is: "tabmail-tab" });
         tab.tabNode = t;
@@ -1019,6 +1032,18 @@
           t.linkedPanel = tab.panel.id;
         }
 
+        // Set the tabId after defining a <browser> and before notifications.
+        let browser = this.getBrowserForTab(tab);
+        if (browser && !tab.browser) {
+          tab.browser = browser;
+          if (!tab.linkedBrowser) {
+            tab.linkedBrowser = browser;
+          }
+        }
+        if (tab.browser && !background) {
+          tab.browser._activeTabId = tab.tabId;
+        }
+
         let restoreState = this._restoringTabState;
         for (let tabMonitor of this.tabMonitors) {
           if (
@@ -1063,9 +1088,8 @@
         });
         t.dispatchEvent(evt);
         delete tab.beforeTabOpen;
-        // Register browser progress listeners
-        let browser = this.getBrowserForTab(tab);
 
+        // Register browser progress listeners
         if (browser && !browser._progressListenerAdded) {
           // It would probably be better to have the tabs register this listener, since the
           // browser can change. This wasn't trivial to do while implementing basic WebExtension
@@ -1677,6 +1701,17 @@
         let showTabFunc = tab.mode.showTab || tab.mode.tabType.showTab;
         showTabFunc.call(tab.mode.tabType, tab);
 
+        let browser = this.getBrowserForTab(tab);
+        if (browser && !tab.browser) {
+          tab.browser = browser;
+          if (!tab.linkedBrowser) {
+            tab.linkedBrowser = browser;
+          }
+        }
+        if (tab.browser) {
+          tab.browser._activeTabId = tab.tabId;
+        }
+
         for (let tabMonitor of this.tabMonitors) {
           tabMonitor.onTabSwitched(tab, oldTab);
         }

mail/components/extensions/parent/ext-mail.js

@@ -399,7 +399,7 @@ class TabTracker extends TabTrackerBase {
     super();
 
     this._tabs = new WeakMap();
-    this._browsers = new WeakMap();
+    this._browsers = new Map();
     this._tabIds = new Map();
     this._nextId = 1;
     this._movingTabs = new Map();
@@ -457,18 +457,19 @@ class TabTracker extends TabTrackerBase {
    * @return {Integer}                  The tab's numeric ID
    */
   getBrowserTabId(browser) {
-    let id = this._browsers.get(browser);
+    let id = this._browsers.get(`${browser.id}#${browser._activeTabId}`);
     if (id) {
       return id;
     }
 
     let tabmail = browser.ownerDocument.getElementById("tabmail");
     let tab =
-      tabmail && tabmail.tabInfo.find(info => getTabBrowser(info) == browser);
+      tabmail &&
+      tabmail.tabInfo.find(info => info.tabId == browser._activeTabId);
 
     if (tab) {
       id = this.getId(tab);
-      this._browsers.set(browser, id);
+      this._browsers.set(`${browser.id}#${tab.tabId}`, id);
       return id;
     }
     return -1;
@@ -484,7 +485,7 @@ class TabTracker extends TabTrackerBase {
     this._tabs.set(nativeTabInfo, id);
     let browser = getTabBrowser(nativeTabInfo);
     if (browser) {
-      this._browsers.set(browser, id);
+      this._browsers.set(`${browser.id}#${nativeTabInfo.tabId}`, id);
     }
     this._tabIds.set(id, nativeTabInfo);
   }
@@ -499,6 +500,7 @@ class TabTracker extends TabTrackerBase {
     let id = this._tabs.get(nativeTabInfo);
     if (id) {
       this._tabs.delete(nativeTabInfo);
+      this._browsers.delete(`${nativeTabInfo.browser.id}#${nativeTabInfo.tabId}`);
       if (this._tabIds.get(id) === nativeTabInfo) {
         this._tabIds.delete(id);
       }
@@ -539,7 +541,6 @@ class TabTracker extends TabTrackerBase {
         // dispatched.
         let tabmail = event.target.ownerDocument.getElementById("tabmail");
         let currentTab = tabmail.selectedTab;
-
         // We need to delay sending this event until the next tick, since the
         // tab does not have its final index when the TabOpen event is dispatched.
         Promise.resolve().then(() => {
@@ -969,7 +970,7 @@ class TabmailTab extends Tab {
 
   /** Returns the favIcon, without permission checks. */
   get _favIconUrl() {
-    return this.browser.mIconURL;
+    return this.browser?.mIconURL;
   }
 
   /** Returns the tabmail element for the tab. */