chainntnfs: always notify txns before block

This commit changes the order of notifications when a relevant tx is
found in a block and now we will always notify the tx subscribers before
notifying the block, which has implications in the upcoming blockbeat.

When a block notification is subscribed via `RegisterBlockEpochNtfn` and
a confirm or spend is subscribed via `RegisterConfirmationsNtfn` or
`RegisterSpendNtfn`, we would always notify the block first before the
tx, causing the subsystem to think there's no relevant txns found in
this block, while the notifications are sent later. We now fix it by
always sending the txns notifications first, so the subsystem can
receive the txns, process them, then attempt to advance its state based
on the block received.

chainntnfs/bitcoindnotify/bitcoind.go

@@ -665,8 +665,14 @@ func (b *BitcoindNotifier) handleBlockConnected(block chainntnfs.BlockEpoch) err
 	// satisfy any client requests based upon the new block.
 	b.bestBlock = block
 
+	err = b.txNotifier.NotifyHeight(uint32(block.Height))
+	if err != nil {
+		return fmt.Errorf("unable to notify height: %w", err)
+	}
+
 	b.notifyBlockEpochs(block.Height, block.Hash, block.BlockHeader)
-	return b.txNotifier.NotifyHeight(uint32(block.Height))
+
+	return nil
 }
 
 // notifyBlockEpochs notifies all registered block epoch clients of the newly

chainntnfs/btcdnotify/btcd.go

@@ -725,11 +725,16 @@ func (b *BtcdNotifier) handleBlockConnected(epoch chainntnfs.BlockEpoch) error {
 	// satisfy any client requests based upon the new block.
 	b.bestBlock = epoch
 
+	err = b.txNotifier.NotifyHeight(uint32(epoch.Height))
+	if err != nil {
+		return fmt.Errorf("unable to notify height: %w", err)
+	}
+
 	b.notifyBlockEpochs(
 		epoch.Height, epoch.Hash, epoch.BlockHeader,
 	)
 
-	return b.txNotifier.NotifyHeight(uint32(epoch.Height))
+	return nil
 }
 
 // notifyBlockEpochs notifies all registered block epoch clients of the newly

chainntnfs/neutrinonotify/neutrino.go

@@ -689,10 +689,16 @@ func (n *NeutrinoNotifier) handleBlockConnected(newBlock *filteredBlock) error {
 	n.bestBlock.Height = int32(newBlock.height)
 	n.bestBlock.BlockHeader = newBlock.header
 
+	err = n.txNotifier.NotifyHeight(newBlock.height)
+	if err != nil {
+		return fmt.Errorf("unable to notify height: %w", err)
+	}
+
 	n.notifyBlockEpochs(
 		int32(newBlock.height), &newBlock.hash, newBlock.header,
 	)
-	return n.txNotifier.NotifyHeight(newBlock.height)
+
+	return nil
 }
 
 // getFilteredBlock is a utility to retrieve the full filtered block from a block epoch.