[Bug]: Short-circuit evaluation bug in TaskManager

[lukehinds]

What happened?

Unless I have misunderstood the intent, there maybe an unintended short-circuit evaluation in the conditional assignment of self.context_id

a2a-python/src/a2a/server/tasks/task_manager.py

Lines 110 to 111 in 4050b81

	if not self.context_id and self.context_id != event.contextId:
	self.context_id = event.contextId

1. When self.context_id is falsy (None, empty string, etc.), then thenot clause for self.context_id evaluates to True

   • Due to short-circuit evaluation care of and, Python never evaluates the second part: self.context_id != event.contextId
   • The condition becomes ~~ True and = True. ~~
   • The code sets self.context_id = event.contextId (which is correct behavior), ok so far.

2. When self.context_id has a value:

   • the not in self.context_id evaluates to False
   • Due to short-circuit evaluation, the entire condition becomes False
   • So context ID validation self.context_id != event.contextId never runs

So the current code will never detect mismatched context IDs because the validation check part is unreachable when self.context_id already has a value. Like I say though I might be wrong and forgive wasting time if so.

I think something like this should do the job:

         if not self.task_id:
             self.task_id = task_id_from_event
-        if not self.context_id and self.context_id != event.contextId:
+        if self.context_id and self.context_id != event.contextId:
+            raise ServerError(
+                error=InvalidParamsError(
+                    message=f"Context in event doesn't match TaskManager: {self.context_id} : {event.contextId}"
+                )
+            )
+        if not self.context_id:
             self.context_id = event.contextId

Relevant log output

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