Issue 4721 - Use IndexedDB for storage in Edge

lib/io.js

Index: lib/io.js
===================================================================
--- a/lib/io.js
+++ b/lib/io.js
@@ -25,32 +25,45 @@
 function loadFile(file, successCallback, errorCallback)
 {
   let key = fileToKey(file);
-
-  ext.storage.get([key], function(items)
+  // Make sure we do not have subscriptions in localStorage from older
+  // versions first
+  let entry = localStorage.getItem(key);
+  if (typeof entry == "string")
   {
-    let entry = items[key];
-
-    if (entry)
-      successCallback(entry);
+    try
+    {
+      entry = JSON.parse(entry);
+    }
+    catch(err) 
+    {
+      setTimeout(errorCallback(new Error("File is corrupted")));
+      return;
+    }
+    setTimeout(successCallback(entry));
+    return;
+  }
+  // Now try to read from IndexedDB
+  localforage.getItem(key, function(err, value) 
+  {
+    if (err || !value)
+      errorCallback(new Error("File doesn't exist"));
     else
-      errorCallback(new Error("File doesn't exist"));
+      successCallback(value);
   });
 }
 
 function saveFile(file, data, callback)
 {
-  ext.storage.set(
-    fileToKey(file),
-    {
-      content: Array.from(data),
-      lastModified: Date.now()
-    },
-    callback
-  );
+  var key = fileToKey(file);
+  var entry = {
+    lastModified: Date.now(),
+    content: Array.from(data)
+  };
+
+  localStorage.removeItem(key);
+  localforage.setItem(key, entry, callback);
 }
-
-exports.IO =
-{
+exports.IO = {

[kzar, 2016/12/19 13:31:04]

Nit: looks like you missed this change, please could you move the { back?

   resolveFilePath: function(path)
   {
     return new FakeFile(path);
@@ -60,9 +73,11 @@
   {
     function onLoaded(entry)
     {
-      for (let line of entry.content)
-        listener.process(line);
-
+      if ("content" in entry)
+      {
+        for (let line of entry.content)
+          listener.process(line);
+      }
       listener.process(null);
       callback(null);
     }
@@ -82,7 +97,7 @@
       saveFile(toFile, entry.content, callback);
     }
 
-    loadFile(fromFile, onLoaded, callback);
+    loadFile(file, onLoaded, callback);

[kzar, 2016/12/19 13:31:04]

Seems to be a mistake? (Same below.)

[Oleksandr, 2016/12/20 00:18:28]

Yep. We don't use any of these functions anyway, so it went unnoticed. In fact
the whole storage code can be refactored now that we don't use backups.

   },
 
   renameFile: function(fromFile, newName, callback)
@@ -95,7 +110,7 @@
       });
     }
 
-    loadFile(fromFile, onLoaded, callback);
+    loadFile(file, onLoaded, callback);
   },
 
   removeFile: function(file, callback)