asyncio.ensure_future(result) creates a task with only a weak ref in
the event loop's task table. After the carrier raises CancelledError,
the local 'task' variable goes out of scope and the loop can GC the
handler before it finishes — the exact 'handler killed mid-flight'
class we are fixing, just via GC instead of cancellation.
Add _detached_fatal_tasks set on BasePlatformAdapter (matching the
gateway-level pattern in _handle_adapter_fatal_error). Uses getattr
fallback for test stubs built via object.__new__().
When an adapter escalates a retryable fatal error from inside one of its
own tasks (e.g. Telegram's _polling_error_task after exhausting polling
network retries), the gateway's _handle_adapter_fatal_error tears the
adapter down via disconnect() — which cancels that very task. The
propagating CancelledError killed the handler between popping the
adapter from the adapter map and queueing the platform in
_failed_platforms, leaving a zombie gateway: process alive, zero
connected platforms, zero pending retries, until a manual restart.
Run the handler as a detached task under asyncio.shield so carrier
cancellation no longer aborts teardown/queueing mid-flight. The carrier
still observes CancelledError (teardown semantics unchanged); only the
handler is protected. A done-callback consumes the detached task's
exception to avoid 'Task exception was never retrieved' noise.
Fixes#81335
kshitij
gregorustar-maker