Better error handling of errors when a world fails to open.

A common case is a corrupt (or empty) level.dat file.  This condition
wasn't properly caught, yielding a less-than-useful stack trace.  Even
more concerning is that this could happen when a user is just running
"overviewer.py" to get a world listing.

This has been fixed to improve the user experience

overviewer.py

@@ -41,6 +41,7 @@ from overviewer_core import optimizeimages, world
 from overviewer_core import configParser, tileset, assetmanager, dispatcher
 from overviewer_core import cache
 from overviewer_core import observer
+from overviewer_core.nbt import CorruptNBTError
 
 helptext = """
 %prog [--rendermodes=...] [options] <World> <Output Dir>
@@ -466,7 +467,12 @@ dir but you forgot to put quotes around the directory, since it contains spaces.
         try:
             w = worldcache[render['world']]
         except KeyError:
-            w = world.World(render['world'])
+            try:
+                w = world.World(render['world'])
+            except CorruptNBTError, e:
+                logging.error("Failed to open world %r", render['world'])
+                raise e
+
             worldcache[render['world']] = w
 
         # find or create the textures object
@@ -595,10 +601,16 @@ def list_worlds():
                 continue
             except ValueError:
                 pass
-        timestamp = time.strftime("%Y-%m-%d %H:%M",
+        if info['LastPlayed'] > 0:
+            timestamp = time.strftime("%Y-%m-%d %H:%M",
                                   time.localtime(info['LastPlayed'] / 1000))
-        playtime = info['Time'] / 20
-        playstamp = '%d:%02d' % (playtime / 3600, playtime / 60 % 60)
+        else:
+            timestamp = ""
+        if info['Time'] > 0:
+            playtime = info['Time'] / 20
+            playstamp = '%d:%02d' % (playtime / 3600, playtime / 60 % 60)
+        else:
+            playstamp = ""
         path = info['path']
         print(formatString % (name, playstamp, timestamp, path))
 

overviewer_core/nbt.py

@@ -189,7 +189,7 @@ class NBTFileReader(object):
             payload = self._read_tag_compound()
             
             return (name, payload)
-        except (struct.error, ValueError), e:
+        except (struct.error, ValueError, TypeError), e:
             raise CorruptNBTError("could not parse nbt: %s" % (str(e),))
 
 # For reference, the MCR format is outlined at

overviewer_core/world.py

@@ -792,9 +792,16 @@ def get_worlds():
     for dir in os.listdir("."):
         world_dat = os.path.join(dir, "level.dat")
         if not os.path.exists(world_dat): continue
-        info = nbt.load(world_dat)[1]
-        info['Data']['path'] = os.path.join(".", dir).decode(loc)
-        if 'LevelName' in info['Data'].keys():
-            ret[info['Data']['LevelName']] = info['Data']
+        world_path = os.path.join(".", dir)
+        try:
+            info = nbt.load(world_dat)[1]
+            info['Data']['path'] = world_path.decode(loc)
+            if 'LevelName' in info['Data'].keys():
+                ret[info['Data']['LevelName']] = info['Data']
+        except nbt.CorruptNBTError:
+            ret[os.path.basename(world_path).decode(loc) + " (corrupt)"] = {'path': world_path.decode(loc),
+                    'LastPlayed': 0,
+                    'Time': 0,
+                    'IsCorrupt': True}
 
     return ret