How to open two indexeddb stores, one after another?

opening_indexeddb_stores.dart

  Database db;
  
  window.indexedDB.deleteDatabase('justtesting')
  .then((_) {
    print('opening');
    return window.indexedDB.open('justtesting', version: 1,
        onUpgradeNeeded: (e) {
          print('upgrading to v1');
          Database d = e.target.result as Database;
          d.createObjectStore('store1');
        },
        onBlocked: (e) => print('blocked on 1'));
  })
  .then((_db) => db = _db)
  .then((_) => db.close())
  .then((_) {
      return window.indexedDB.open('justtesting', version: 2,
        onUpgradeNeeded: (e) {
          print('upgrading to v2');
          Database d = e.target.result as Database;
          d.createObjectStore('store2');
        },
        onBlocked: (e) => print('blocked on 2'));
    })
  .then((_db) => db = _db)
  .then((_) {
    print('fetching data');
    Transaction txn = db.transaction('store1', 'readonly');
    ObjectStore store = txn.objectStore('store1');
    store.getObject('1').then(print);
    return txn.completed;
  })
  .then((_) {
    print('all done');
  })
  .catchError(print);

This has a bug. It gets stuck at 'blocked on 2'

And I fixed it by closing the db before I opened it again.

Nit:
Transaction txn = db.transaction('store1', 'readonly');
ObjectStore store = txn.objectStore('store1');
store.getObject('1').then(print);
return txn.completed;

In this, if the getObject('1') fails, then it'll get lost because the transaction still succeeds.

To avoid forking the future chain, use:

Transaction txn = db.transaction('store1', 'readonly');
ObjectStore store = txn.objectStore('store1');
return store.getObject('1').then((value) {
  print(value);
  return txn.completed;
});

Also for reference, the upgrade scenario is tested with:
https://code.google.com/p/dart/source/browse/branches/bleeding_edge/dart/tests/html/indexeddb_1_test.dart#16

you're block because you open with 2 differents version number :

from https://developer.mozilla.org/en-US/docs/IndexedDB/Using_IndexedDB

  // Make sure to add a handler to be notified if another page requests a version
  // change. We must close the database. This allows the other page to upgrade the database.
  // If you don't do this then the upgrade won't happen until the user close the tab.
  db.onversionchange = function(event) {
    db.close();
    alert("A new version of this page is ready. Please reload!");
  };