Issue 6775 - Work around filter data stored in IndexedDB getting lost on Microsoft Edge

lib/ioIndexedDB.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 139 matching lines @@
   };
 }
 
 function getObjectStore(dbInstance, storeName)
 {
   return dbInstance
     .transaction([storeName], IDBTransaction.READ_WRITE)
     .objectStore(storeName);
 }
 
+function reestablishConnection(dbInstance, retries = 10)
+{
+  dbInstance.close();
+  db = openDB(dbConfig);
+
+  return db.catch(err =>
+  {
+    if (!retries)
+      throw err;
+
+    return reestablishConnection(dbInstance, --retries);
+  });
+}
+
 function getFile(fileName, dbInstance, storeName)
 {
+  return getFromIndexedDB(fileToKey(fileName), dbInstance, storeName)
+    .then(indexedDBResult =>
+    {
+      if (!indexedDBResult)
+      {
+        const {IndexedDBBackup} = require("./indexedDBBackup");
+
+        return IndexedDBBackup.getBackupData()
+          .then(backupData =>
+            saveFile(
+              {
+                fileName: fileToKey(fileName),
+                content: backupData.content,
+                lastModified: backupData.lastModified
+              },
+              dbInstance,
+              storeName).then(() => backupData)
+          );
+      }
+      return indexedDBResult;
+    });
+}
+
+function getFromIndexedDB(fileName, dbInstance, storeName)
+{
   return new Promise((resolve, reject) =>
   {
     let store = getObjectStore(dbInstance, storeName);
-    let req = store.get(fileToKey(fileName));
+    let req = store.get(fileName);
 
-    req.onsuccess = event =>
-    {
-      let {result} = event.currentTarget;
-
-      if (result)
-        resolve(result);
-      else
-        reject({type: "NoSuchFile"});
-    };
-    req.onerror = reject;
+    req.onsuccess = event => resolve(event.currentTarget.result);
+    req.onerror = event => reject(event.target.error);
+  })
+  .catch(error =>
+  {
+    if (error.name == "UnknownError")
+      return reestablishConnection(dbInstance).then(() => undefined);
   });
 }
 
 function saveFile(data, dbInstance, storeName)
 {
   return new Promise((resolve, reject) =>
   {
     let store = getObjectStore(dbInstance, storeName);
     let req = store.put(data);
 
     req.onsuccess = resolve;
-    req.onerror = reject;
+    req.onerror = event => reject(event.target.error);
+  })
+  .catch(error =>
+  {
+    if (error.name == "UnknownError")
+    {
+      return reestablishConnection(dbInstance).then(newDbInstance =>
+        saveFile(data, newDbInstance, storeName)
+      );
+    }
   });
 }
 
 function deleteFile(fileName, dbInstance, storeName)
 {
   return new Promise((resolve, reject) =>
   {
     let store = getObjectStore(dbInstance, storeName);
     let req = store.delete(fileToKey(fileName));
 
     req.onsuccess = resolve;
-    req.onerror = reject;
+    req.onerror = event => reject(event.target.error);
+  })
+  .catch(error =>
+  {
+    if (error.name == "UnknownError")
+      return reestablishConnection(dbInstance);
   });
 }
 
 exports.IO =
 {
   /**
    * Writes text lines to a file.
    * @param {string} fileName
    *    Name of the file to be written
    * @param {Iterable.<string>} data
@@ skipping 83 matching lines @@
                 fileName: fileToKey(newName),
                 content: fileData.content,
                 lastModified: fileData.lastModified
               },
               dbInstance,
               dbConfig.storeName))
           .then(() => deleteFile(fromFile, dbInstance, dbConfig.storeName))));
   }
 };