reorg detection is may not handle blocks off the top case.

[zancas]

This reorg detection is only expected to run at initialization time. All other things being equal it would be nice to break it out cleanly into an obvious initialization scope.

zingolib/pepper-sync/src/sync.rs

Lines 1452 to 1493 in 9b2bb0f

	{
	tracing::info!("Re-org detected.");
	let sync_state = wallet
	.get_sync_state_mut()
	.map_err(SyncError::WalletError)?;
	let last_known_chain_height = sync_state
	.last_known_chain_height()
	.expect("scan ranges should be non-empty in this scope");
	// reset scan range from `Scanning` to `Verify`
	state::set_scan_priority(
	sync_state,
	scan_range.block_range(),
	ScanPriority::Verify,
	);
	// extend verification range to VERIFY_BLOCK_RANGE_SIZE blocks below current verification range
	let verification_start = state::set_verify_scan_range(
	sync_state,
	height - 1,
	state::VerifyEnd::VerifyHighest,
	)
	.block_range()
	.start;
	state::merge_scan_ranges(sync_state, ScanPriority::Verify);
	if initial_unscanned_height - verification_start > MAX_REORG_ALLOWANCE {
	clear_wallet_data(wallet)?;
	return Err(ServerError::ChainVerificationError.into());
	}
	truncate_wallet_data(wallet, verification_start - 1)?;
	state::set_initial_state(
	consensus_parameters,
	fetch_request_sender.clone(),
	wallet,
	last_known_chain_height,
	)
	.await?;
	} else {

[Oscar-Pepper]

I dont believe there is any issue with the current state of the code for detecting re-org for data already in the wallet. I think this can be closed but an issue be opened that describes the specific case where re-org has happened during sync where blocks have been knocked off the top (the chain is actually lower than the chain height returned from server at start of sync). in this case sync will try to get a range of blocks where all of those blocks dont exist on the best chain. this error can be recovered from with the correct logic. I assume this is an extremely rare edge case as the chain tip is synced first so the time window between sync starting and these blocks being synced is very small. my understanding is re-org actually reducing the height of the chain is rare also.