block-sync: poll: make best known chain tip optional

Author: valentinewallace

lightning-block-sync/src/lib.rs

@@ -235,7 +235,7 @@ impl<'a, P: Poll, C: Cache, L: Deref> SpvClient<'a, P, C, L> where L::Target: ch
 	/// Returns the best polled chain tip relative to the previous best known tip and whether any
 	/// blocks were indeed connected or disconnected.
 	pub async fn poll_best_tip(&mut self) -> BlockSourceResult<(ChainTip, bool)> {
-		let chain_tip = self.chain_poller.poll_chain_tip(self.chain_tip).await?;
+		let chain_tip = self.chain_poller.poll_chain_tip(Some(self.chain_tip)).await?;
 		let blocks_connected = match chain_tip {
 			ChainTip::Common => false,
 			ChainTip::Better(chain_tip) => {

lightning-block-sync/src/poll.rs

@@ -15,7 +15,7 @@ use std::ops::DerefMut;
 /// [`ChainPoller`]: ../struct.ChainPoller.html
 pub trait Poll {
 	/// Returns a chain tip in terms of its relationship to the provided chain tip.
-	fn poll_chain_tip<'a>(&'a mut self, best_known_chain_tip: ValidatedBlockHeader) ->
+	fn poll_chain_tip<'a>(&'a mut self, best_known_chain_tip: Option<ValidatedBlockHeader>) ->
 		AsyncBlockSourceResult<'a, ChainTip>;
 
 	/// Returns the header that preceded the given header in the chain.
@@ -174,22 +174,28 @@ impl<B: DerefMut<Target=T> + Sized + Sync + Send, T: BlockSource> ChainPoller<B,
 }
 
 impl<B: DerefMut<Target=T> + Sized + Sync + Send, T: BlockSource> Poll for ChainPoller<B, T> {
-	fn poll_chain_tip<'a>(&'a mut self, best_known_chain_tip: ValidatedBlockHeader) ->
+	fn poll_chain_tip<'a>(&'a mut self, best_known_chain_tip: Option<ValidatedBlockHeader>) ->
 		AsyncBlockSourceResult<'a, ChainTip>
 	{
 		Box::pin(async move {
 			let (block_hash, height) = self.block_source.get_best_block().await?;
-			if block_hash == best_known_chain_tip.header.block_hash() {
-				return Ok(ChainTip::Common);
+			if let Some(curr_tip) = best_known_chain_tip {
+				if block_hash == curr_tip.header.block_hash() {
+					return Ok(ChainTip::Common);
+				}
 			}
 
 			let chain_tip = self.block_source
 				.get_header(&block_hash, height).await?
 				.validate(block_hash)?;
-			if chain_tip.chainwork > best_known_chain_tip.chainwork {
-				Ok(ChainTip::Better(chain_tip))
+			if let Some(curr_tip) = best_known_chain_tip {
+				if chain_tip.chainwork > curr_tip.chainwork {
+					Ok(ChainTip::Better(chain_tip))
+				} else {
+					Ok(ChainTip::Worse(chain_tip))
+				}
 			} else {
-				Ok(ChainTip::Worse(chain_tip))
+				Ok(ChainTip::Better(chain_tip))
 			}
 		})
 	}
@@ -234,7 +240,7 @@ mod tests {
 	#[tokio::test]
 	async fn poll_empty_chain() {
 		let mut chain = Blockchain::default().with_height(0);
-		let best_known_chain_tip = chain.tip();
+		let best_known_chain_tip = Some(chain.tip());
 		chain.disconnect_tip();
 
 		let mut poller = ChainPoller::new(&mut chain, Network::Bitcoin);
@@ -250,7 +256,7 @@ mod tests {
 	#[tokio::test]
 	async fn poll_chain_without_headers() {
 		let mut chain = Blockchain::default().with_height(1).without_headers();
-		let best_known_chain_tip = chain.at_height(0);
+		let best_known_chain_tip = Some(chain.at_height(0));
 
 		let mut poller = ChainPoller::new(&mut chain, Network::Bitcoin);
 		match poller.poll_chain_tip(best_known_chain_tip).await {
@@ -265,7 +271,7 @@ mod tests {
 	#[tokio::test]
 	async fn poll_chain_with_invalid_pow() {
 		let mut chain = Blockchain::default().with_height(1);
-		let best_known_chain_tip = chain.at_height(0);
+		let best_known_chain_tip = Some(chain.at_height(0));
 
 		// Invalidate the tip by changing its target.
 		chain.blocks.last_mut().unwrap().header.bits =
@@ -284,7 +290,7 @@ mod tests {
 	#[tokio::test]
 	async fn poll_chain_with_malformed_headers() {
 		let mut chain = Blockchain::default().with_height(1).malformed_headers();
-		let best_known_chain_tip = chain.at_height(0);
+		let best_known_chain_tip = Some(chain.at_height(0));
 
 		let mut poller = ChainPoller::new(&mut chain, Network::Bitcoin);
 		match poller.poll_chain_tip(best_known_chain_tip).await {
@@ -299,7 +305,7 @@ mod tests {
 	#[tokio::test]
 	async fn poll_chain_with_common_tip() {
 		let mut chain = Blockchain::default().with_height(0);
-		let best_known_chain_tip = chain.tip();
+		let best_known_chain_tip = Some(chain.tip());
 
 		let mut poller = ChainPoller::new(&mut chain, Network::Bitcoin);
 		match poller.poll_chain_tip(best_known_chain_tip).await {
@@ -319,7 +325,7 @@ mod tests {
 		assert_eq!(best_known_chain_tip.chainwork, worse_chain_tip.chainwork);
 
 		let mut poller = ChainPoller::new(&mut chain, Network::Bitcoin);
-		match poller.poll_chain_tip(best_known_chain_tip).await {
+		match poller.poll_chain_tip(Some(best_known_chain_tip)).await {
 			Err(e) => panic!("Unexpected error: {:?}", e),
 			Ok(tip) => assert_eq!(tip, ChainTip::Worse(worse_chain_tip)),
 		}
@@ -328,7 +334,7 @@ mod tests {
 	#[tokio::test]
 	async fn poll_chain_with_worse_tip() {
 		let mut chain = Blockchain::default().with_height(1);
-		let best_known_chain_tip = chain.tip();
+		let best_known_chain_tip = Some(chain.tip());
 
 		chain.disconnect_tip();
 		let worse_chain_tip = chain.tip();
@@ -348,9 +354,20 @@ mod tests {
 		let better_chain_tip = chain.tip();
 
 		let mut poller = ChainPoller::new(&mut chain, Network::Bitcoin);
-		match poller.poll_chain_tip(best_known_chain_tip).await {
+		match poller.poll_chain_tip(Some(best_known_chain_tip)).await {
 			Err(e) => panic!("Unexpected error: {:?}", e),
 			Ok(tip) => assert_eq!(tip, ChainTip::Better(better_chain_tip)),
 		}
 	}
+
+	#[tokio::test]
+	async fn poll_chain_no_best_tip() {
+		let mut chain = Blockchain::default().with_height(1);
+		let chain_tip = chain.tip();
+		let mut poller = ChainPoller::new(&mut chain, Network::Bitcoin);
+		match poller.poll_chain_tip(None).await {
+			Err(e) => panic!("Unexpected error: {:?}", e),
+			Ok(tip) => assert_eq!(tip, ChainTip::Better(chain_tip)),
+		}
+	}
 }