This reverts commit dc6c481406 as it introduced its own issue:
while add_address was running on one thread, synchronizer._reset could be running on another,
and by the time the "enqueue" coro would run, it would use a new add_queue and
addr would not be in requested_addrs anymore...
```
I/w | wallet.Standard_Wallet.[test_segwit_2] | starting taskgroup.
I | lnworker.LNWallet.[test_segwit_2] | starting taskgroup.
E/i | interface.[testnet.qtornado.com:51002] | Exception in run: KeyError('tb1q3wmgf8n5eettnj50pzgnfrrpdpjmwn37x7nzsc5780kk4je9v4hspym8mu')
Traceback (most recent call last):
File ".../electrum/electrum/util.py", line 1243, in wrapper
return await func(*args, **kwargs)
File ".../electrum/electrum/interface.py", line 506, in wrapper_func
return await func(self, *args, **kwargs)
File ".../electrum/electrum/interface.py", line 529, in run
await self.open_session(ssl_context)
File ".../electrum/electrum/interface.py", line 679, in open_session
async with self.taskgroup as group:
File ".../aiorpcX/aiorpcx/curio.py", line 304, in __aexit__
await self.join()
File ".../electrum/electrum/util.py", line 1339, in join
task.result()
File ".../electrum/electrum/synchronizer.py", line 80, in _run_tasks
async with taskgroup as group:
File ".../aiorpcX/aiorpcx/curio.py", line 304, in __aexit__
await self.join()
File ".../electrum/electrum/util.py", line 1339, in join
task.result()
File ".../electrum/electrum/synchronizer.py", line 127, in subscribe_to_address
self.requested_addrs.remove(addr)
KeyError: 'tb1q3wmgf8n5eettnj50pzgnfrrpdpjmwn37x7nzsc5780kk4je9v4hspym8mu'
```
AddressSynchronizer.add_address called synchronizer.add, which would only
schedule adding the addr to the Synchronizer in the next event loop iter.
If during that time, the synchronizer called adb.set_up_to_date(True),
the wallet would falsely believe and advertise itself as up_to_date
(as the wallet would see wallet.synchronize not creating new addresses,
and adb (via synchronizer) telling it is up_to_date).
Moments later, the synchronizer._add_address is finally executed and
up_to_date=False propagates out synchronizer->adb->wallet.
