Handle the possibility of a drop having no benefits

inventory.py

@@ -64,7 +64,7 @@ class BaseDrop:
         self.id: str = data["id"]
         self.name: str = data["name"]
         self.campaign: DropsCampaign = campaign
-        self.benefits: list[Benefit] = [Benefit(b) for b in data["benefitEdges"]]
+        self.benefits: list[Benefit] = [Benefit(b) for b in (data["benefitEdges"] or [])]
         self.starts_at: datetime = timestamp(data["startAt"])
         self.ends_at: datetime = timestamp(data["endAt"])
         self.claim_id: str | None = None
@@ -89,7 +89,7 @@ class BaseDrop:
             and all(self.starts_at <= dt < self.ends_at for dt in dts)
         ):
             self.is_claimed = True
-        self._precondition_drops: list[str] = [d["id"] for d in (data["preconditionDrops"] or [])]
+        self.precondition_drops: list[str] = [d["id"] for d in (data["preconditionDrops"] or [])]
 
     def __repr__(self) -> str:
         if self.is_claimed:
@@ -103,13 +103,15 @@ class BaseDrop:
     @cached_property
     def preconditions_met(self) -> bool:
         campaign = self.campaign
-        return all(campaign.timed_drops[pid].is_claimed for pid in self._precondition_drops)
+        return all(campaign.timed_drops[pid].is_claimed for pid in self.precondition_drops)
 
     def _base_earn_conditions(self) -> bool:
         # define when a drop can be earned or not
         return (
             self.preconditions_met  # preconditions are met
             and not self.is_claimed  # isn't already claimed
+            # has at least one benefit, or participates in a preconditions chain
+            and (bool(self.benefits) or self.id in self.campaign.preconditions_chain())
         )
 
     def _base_can_earn(self) -> bool:
@@ -247,7 +249,7 @@ class TimedDrop(BaseDrop):
         return self.required_minutes + max(
             (
                 self.campaign.timed_drops[pid].total_required_minutes
-                for pid in self._precondition_drops
+                for pid in self.precondition_drops
             ),
             default=0,
         )
@@ -257,7 +259,7 @@ class TimedDrop(BaseDrop):
         return self.remaining_minutes + max(
             (
                 self.campaign.timed_drops[pid].total_remaining_minutes
-                for pid in self._precondition_drops
+                for pid in self.precondition_drops
             ),
             default=0,
         )
@@ -413,6 +415,13 @@ class DropsCampaign:
     def availability(self) -> float:
         return min(d.availability for d in self.drops)
 
+    def preconditions_chain(self) -> set[str]:
+        return set(
+            chain.from_iterable(
+                drop.precondition_drops for drop in self.drops if not drop.is_claimed
+            )
+        )
+
     def _on_claim(self) -> None:
         invalidate_cache(self, "finished", "claimed_drops", "remaining_drops")
         for drop in self.drops: