Bug 1761445 - TabManager.getBrowsingContextById should not return clo…

…sed browsing contexts. r=jdescottes,webdriver-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D225303

remote/shared/TabManager.sys.mjs

@@ -231,15 +231,22 @@ class TabManagerClass {
    * @param {string} id
    *     A browsing context unique id (created by getIdForBrowsingContext).
    * @returns {BrowsingContext=}
-   *     The browsing context found for this id, null if none was found.
+   *     The browsing context found for this id, null if none was found or
+   *     browsing context is discarded.
    */
   getBrowsingContextById(id) {
     const browser = this.getBrowserById(id);
+    let browsingContext;
     if (browser) {
-      return browser.browsingContext;
+      browsingContext = browser.browsingContext;
+    } else {
+      browsingContext = BrowsingContext.get(id);
     }
 
-    return BrowsingContext.get(id);
+    if (!browsingContext || browsingContext.isDiscarded) {
+      return null;
+    }
+    return browsingContext;
   }
 
   /**

remote/shared/test/browser/browser_TabManager.js

@@ -144,6 +144,27 @@ add_task(async function test_getBrowsingContextById() {
   is(TabManager.getBrowsingContextById(childContextId), contexts[1]);
 });
 
+add_task(async function test_getDiscardedBrowsingContextById() {
+  const tab = await TabManager.addTab();
+  const browser = tab.linkedBrowser;
+  const browsingContext = browser.browsingContext;
+  const contextId = TabManager.getIdForBrowsingContext(browsingContext);
+
+  is(
+    TabManager.getBrowsingContextById(contextId),
+    browsingContext,
+    "Browsing context is accessible by its ID"
+  );
+
+  gBrowser.removeTab(tab);
+
+  is(
+    TabManager.getBrowsingContextById(contextId),
+    null,
+    "Browsing context is no longer accessible after the tab is removed"
+  );
+});
+
 add_task(async function test_getIdForBrowsingContext() {
   const browser = gBrowser.selectedBrowser;