Fix concurrency bugs in unclose MV3 migration

unclose/bg.js

@@ -1,43 +1,56 @@
+// Serialize all storage writes to prevent counter races on rapid tab events.
+var _writeQueue = Promise.resolve();
+function enqueueWrite(asyncFn) {
+  _writeQueue = _writeQueue.then(asyncFn).catch((err) => {
+    console.error('[unclose] storage write failed:', err);
+  });
+  return _writeQueue;
+}
+
 chrome.tabs.onUpdated.addListener(async function(tabId, changeInfo, tab) {
-  await ensureInitialized();
-  var tabKey = "TabList-" + tabId;
-  var currentUrl = tab.url || await storageGet(tabKey);
-  var updates = {};
-  if (tab.url)
-    updates[tabKey] = tab.url;
-  updates["TabIndex-" + tabId] = tab.index;
-  if (tab.favIconUrl)
-    updates["TabFavicon-" + tabId] = tab.favIconUrl;
-  if(tab.title != null && currentUrl)
-    updates["TabTitle-" + tabId] = tab.title;
-  else if (currentUrl)
-    updates["TabTitle-" + tabId] = currentUrl;
-  await storageSet(updates);
+  await enqueueWrite(async () => {
+    await ensureInitialized();
+    var tabKey = "TabList-" + tabId;
+    var currentUrl = tab.url || await storageGet(tabKey);
+    var updates = {};
+    if (tab.url)
+      updates[tabKey] = tab.url;
+    updates["TabIndex-" + tabId] = tab.index;
+    if (tab.favIconUrl)
+      updates["TabFavicon-" + tabId] = tab.favIconUrl;
+    if (tab.title != null)
+      updates["TabTitle-" + tabId] = tab.title;
+    else if (currentUrl)
+      updates["TabTitle-" + tabId] = currentUrl;
+    await storageSet(updates);
+  });
 });
 
-chrome.tabs.onRemoved.addListener(async function(tabId, info)  {
-  await ensureInitialized();
-  // Should we record this tab?
-  var tabKey = "TabList-" + tabId;
-  var state = await storageGet({
-    closeCount: 0,
-    actualCount: 0,
-    [tabKey]: null
+chrome.tabs.onRemoved.addListener(async function(tabId, info) {
+  await enqueueWrite(async () => {
+    await ensureInitialized();
+    // Should we record this tab?
+    var tabKey = "TabList-" + tabId;
+    var state = await storageGet({
+      closeCount: 0,
+      actualCount: 0,
+      [tabKey]: null
+    });
+    var url = state[tabKey];
+    var re = /^(http:|https:|ftp:|file:)/;
+    if (url && re.test(url)) {
+      var closeCount = parseInt(state.closeCount, 10) || 0;
+      var actualCount = (parseInt(state.actualCount, 10) || 0) + 1;
+      var updates = {
+        closeCount: closeCount + 1,
+        actualCount: actualCount
+      };
+      updates["ClosedTab-" + closeCount] = tabId;
+      updates["ClosedTabTime-" + closeCount] = new Date().getTime();
+      await storageSet(updates);
+      await setBadgeText();
+    }
+    else
+      await clear(tabId);
   });
-  var url = state[tabKey];
-  var re = /^(http:|https:|ftp:|file:)/;
-  if (url && re.test(url)) {
-    var closeCount = parseInt(state.closeCount, 10) || 0;
-    var actualCount = (parseInt(state.actualCount, 10) || 0) + 1;
-    var updates = {
-      closeCount: closeCount + 1,
-      actualCount: actualCount
-    };
-    updates["ClosedTab-" + closeCount] = tabId;
-    updates["ClosedTabTime-" + closeCount] = new Date().getTime();
-    await storageSet(updates);
-    await setBadgeText();
-  }
-  else
-    await clear(tabId);
 });

unclose/init.js

@@ -44,10 +44,13 @@ async function init()
   await initialize();
 }
 
-chrome.runtime.onInstalled.addListener(async function() {
-  await init();
+chrome.runtime.onInstalled.addListener(async function(details) {
+  if (details.reason === 'install') await init();
+  else await ensureInitialized();
 });
 
 chrome.runtime.onStartup.addListener(async function() {
-  await init();
+  // chrome.storage.session is cleared automatically on browser restart;
+  // just reset the counters and badge.
+  await initialize();
 });

unclose/popup.js

@@ -131,7 +131,6 @@ function prev() {
 // Show |url| in a new tab.
 async function showUrl(tabId) {
   var state = await storageGet({
-    actualCount: 0,
     ["TabList-" + tabId]: null,
     ["TabIndex-" + tabId]: null
   });
@@ -146,8 +145,11 @@ async function showUrl(tabId) {
 
   await chrome.tabs.create(createProperties);
   await clear(tabId);
+  // Re-read actualCount right before decrementing to minimise the race window
+  // with concurrent onRemoved increments.
+  var currentCount = parseInt(await storageGet("actualCount"), 10) || 0;
   await storageSet({
-    actualCount: Math.max((parseInt(state.actualCount, 10) || 0) - 1, 0)
+    actualCount: Math.max(currentCount - 1, 0)
   });
   await setBadgeText();
   await loadContent();