Fix syncing for Add/remove

ereuse_devicehub/resources/event/models.py

@@ -98,6 +98,9 @@ class Event(Thing):
     For example: an ``Allocate`` is performed to a Computer and this
     relationship is filled with the components the computer had
     at the time of the event.
+    
+    For Add and Remove though, this has another meaning: the components
+    that are added or removed.
     """
     parent_id = Column(BigInteger, ForeignKey(Computer.id))
     parent = relationship(Computer,
@@ -438,6 +441,9 @@ def update_components_event_one(target: EventWithOneDevice, device: Device, __,
     Syncs the :attr:`.Event.components` with the components in
     :attr:`ereuse_devicehub.resources.device.models.Computer.components`.
     """
+    # For Add and Remove, ``components`` have different meanings
+    # see Event.components for more info
+    if not isinstance(target, (Add, Remove)):
         target.components.clear()
         if isinstance(device, Computer):
             target.components |= device.components