When we have tracker events, don't change type with game events.

Fixes #152.

Author: GraylinKim

sc2reader/engine/plugins/context.py

@@ -49,9 +49,12 @@ def handleTargetAbilityEvent(self, event, replay):
 
         if event.target_unit_id in replay.objects:
             event.target = replay.objects[event.target_unit_id]
-            if not event.target.is_type(event.target_unit_type):
+            if not replay.tracker_events and not event.target.is_type(event.target_unit_type):
                 replay.datapack.change_type(event.target, event.target_unit_type, event.frame)
         else:
+            # Often when the target_unit_id is not in replay.objects it is 0 because it
+            # is a target building/destructable hidden by fog of war. Perhaps we can match
+            # it through the fog using location?
             unit = replay.datapack.create_unit(event.target_unit_id, event.target_unit_type, 0x00, event.frame)
             event.target = unit
             replay.objects[event.target_unit_id] = unit

sc2reader/events/game.py

@@ -278,9 +278,12 @@ def __init__(self, frame, pid, data):
         self.target_timer = self.ability_type_data.get('timer', None)
 
         #: Unique id of the target unit. Available for TargetUnit type events.
+        #: This id can be 0 when the target unit is shrouded by fog of war.
         self.target_unit_id = self.ability_type_data.get('unit_tag', None)
 
-        #: A reference to the targetted unit
+        #: A reference to the targetted unit. When the :attr:`target_unit_id` is
+        #: 0 this target unit is a generic, reused fog of war unit of the :attr:`target_unit_type`
+        #: with an id of zero. It should not be confused with a real unit.
         self.target_unit = None
 
         #: Current integer type id of the target unit. Available for TargetUnit type events.