fix(sdk/vm): re-load iavl store from backup if empty (#2568)

This is a hack; during initialization, the iavlStore is backed up to the
baseStore, and it is then recovered in Initialize if the iavlStore is
found to be empty (but there's supposed to be packages inside).

This is a hotfix for test4 non-validator nodes.

It still requires to start up the non-validator node once, with the new
changes applied, with a fresh db

gno.land/pkg/sdk/vm/keeper.go

@@ -118,6 +118,13 @@ func uncachedPackageLoad(
 
 		loadStdlib(stdlibsDir, gnoStore)
 
+		// XXX Quick and dirty to make this function work on non-validator nodes
+		iter := iavlStore.Iterator(nil, nil)
+		for ; iter.Valid(); iter.Next() {
+			baseStore.Set(append(iavlBackupPrefix, iter.Key()...), iter.Value())
+		}
+		iter.Close()
+
 		logger.Debug("Standard libraries initialized",
 			"elapsed", time.Since(start))
 	} else {
@@ -126,6 +133,18 @@ func uncachedPackageLoad(
 		// and memory management across many objects/types/nodes/packages.
 		start := time.Now()
 
+		// XXX Quick and dirty to make this function work on non-validator nodes
+		if isStoreEmpty(iavlStore) {
+			iter := baseStore.Iterator(iavlBackupPrefix, nil)
+			for ; iter.Valid(); iter.Next() {
+				if !bytes.HasPrefix(iter.Key(), iavlBackupPrefix) {
+					break
+				}
+				iavlStore.Set(iter.Key()[len(iavlBackupPrefix):], iter.Value())
+			}
+			iter.Close()
+		}
+
 		m2 := gno.NewMachineWithOptions(
 			gno.MachineOptions{
 				PkgPath: "",
@@ -143,6 +162,17 @@ func uncachedPackageLoad(
 	return gnoStore
 }
 
+var iavlBackupPrefix = []byte("init_iavl_backup:")
+
+func isStoreEmpty(st store.Store) bool {
+	iter := st.Iterator(nil, nil)
+	defer iter.Close()
+	for ; iter.Valid(); iter.Next() {
+		return false
+	}
+	return true
+}
+
 func cachedStdlibLoad(stdlibsDir string, baseStore, iavlStore store.Store) gno.Store {
 	cachedStdlibOnce.Do(func() {
 		cachedStdlibBase = memdb.NewMemDB()