Expose a bindings-compatible BestBlock

UniFFI cannot represent the fixed-size array that upstream's BestBlock
carries via `previous_blocks`, so NodeStatus.current_best_block was
unusable from Swift, Kotlin, and Python once upstream added that field.
Introduce a small ldk-node BestBlock with just hash and height — the
pieces bindings can handle — and expose it in place of the upstream
type on the public API.

Generated with assistance from Claude Code.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jkczyz

bindings/ldk_node.udl

@@ -233,12 +233,6 @@ enum NodeError {
 
 typedef dictionary NodeStatus;
 
-[Remote]
-dictionary BestBlock {
-	BlockHash block_hash;
-	u32 height;
-};
-
 typedef enum BuildError;
 
 [Trait, WithForeign]

src/builder.rs

@@ -22,7 +22,7 @@ use bitcoin::secp256k1::PublicKey;
 use bitcoin::Network;
 use bitcoin_payment_instructions::dns_resolver::DNSHrnResolver;
 use bitcoin_payment_instructions::onion_message_resolver::LDKOnionMessageDNSSECHrnResolver;
-use lightning::chain::{chainmonitor, BestBlock};
+use lightning::chain::{chainmonitor, BestBlock as BlockLocator};
 use lightning::ln::channelmanager::{self, ChainParameters, ChannelManagerReadArgs};
 use lightning::ln::msgs::{RoutingMessageHandler, SocketAddress};
 use lightning::ln::peer_handler::{IgnoringMessageHandler, MessageHandler};
@@ -1696,15 +1696,15 @@ fn build_with_store_internal(
 				channel_monitor_references,
 			);
 			let (_best_block, channel_manager) =
-				<(BestBlock, ChannelManager)>::read(&mut &*reader, read_args).map_err(|e| {
+				<(BlockLocator, ChannelManager)>::read(&mut &*reader, read_args).map_err(|e| {
 					log_error!(logger, "Failed to read channel manager from store: {}", e);
 					BuildError::ReadFailed
 				})?;
 			channel_manager
 		} else {
 			// We're starting a fresh node.
 			let best_block =
-				chain_tip_opt.unwrap_or_else(|| BestBlock::from_network(config.network));
+				chain_tip_opt.unwrap_or_else(|| BlockLocator::from_network(config.network));
 
 			let chain_params = ChainParameters { network: config.network.into(), best_block };
 			channelmanager::ChannelManager::new(

src/chain/bitcoind.rs

@@ -16,7 +16,7 @@ use base64::prelude::BASE64_STANDARD;
 use base64::Engine;
 use bitcoin::{BlockHash, FeeRate, Network, OutPoint, Transaction, Txid};
 use lightning::chain::chaininterface::ConfirmationTarget as LdkConfirmationTarget;
-use lightning::chain::{BestBlock, Listen};
+use lightning::chain::{BestBlock as BlockLocator, Listen};
 use lightning::util::ser::Writeable;
 use lightning_block_sync::gossip::UtxoSource;
 use lightning_block_sync::http::{HttpClientError, JsonResponse};
@@ -325,7 +325,7 @@ impl BitcoindChainSource {
 		}
 	}
 
-	pub(super) async fn poll_best_block(&self) -> Result<BestBlock, Error> {
+	pub(super) async fn poll_best_block(&self) -> Result<BlockLocator, Error> {
 		self.poll_chain_tip().await.map(|tip| tip.to_best_block())
 	}
 

src/chain/mod.rs

@@ -14,7 +14,7 @@ use std::sync::{Arc, Mutex, RwLock};
 use std::time::Duration;
 
 use bitcoin::{Script, Txid};
-use lightning::chain::{BestBlock, Filter};
+use lightning::chain::{BestBlock as BlockLocator, Filter};
 
 use crate::chain::bitcoind::{BitcoindChainSource, UtxoSourceClient};
 use crate::chain::electrum::ElectrumChainSource;
@@ -101,7 +101,7 @@ impl ChainSource {
 		fee_estimator: Arc<OnchainFeeEstimator>, tx_broadcaster: Arc<Broadcaster>,
 		kv_store: Arc<DynStore>, config: Arc<Config>, logger: Arc<Logger>,
 		node_metrics: Arc<RwLock<NodeMetrics>>,
-	) -> Result<(Self, Option<BestBlock>), ()> {
+	) -> Result<(Self, Option<BlockLocator>), ()> {
 		let esplora_chain_source = EsploraChainSource::new(
 			server_url,
 			headers,
@@ -122,7 +122,7 @@ impl ChainSource {
 		fee_estimator: Arc<OnchainFeeEstimator>, tx_broadcaster: Arc<Broadcaster>,
 		kv_store: Arc<DynStore>, config: Arc<Config>, logger: Arc<Logger>,
 		node_metrics: Arc<RwLock<NodeMetrics>>,
-	) -> (Self, Option<BestBlock>) {
+	) -> (Self, Option<BlockLocator>) {
 		let electrum_chain_source = ElectrumChainSource::new(
 			server_url,
 			sync_config,
@@ -142,7 +142,7 @@ impl ChainSource {
 		fee_estimator: Arc<OnchainFeeEstimator>, tx_broadcaster: Arc<Broadcaster>,
 		kv_store: Arc<DynStore>, config: Arc<Config>, logger: Arc<Logger>,
 		node_metrics: Arc<RwLock<NodeMetrics>>,
-	) -> (Self, Option<BestBlock>) {
+	) -> (Self, Option<BlockLocator>) {
 		let bitcoind_chain_source = BitcoindChainSource::new_rpc(
 			rpc_host,
 			rpc_port,
@@ -165,7 +165,7 @@ impl ChainSource {
 		fee_estimator: Arc<OnchainFeeEstimator>, tx_broadcaster: Arc<Broadcaster>,
 		kv_store: Arc<DynStore>, config: Arc<Config>, rest_client_config: BitcoindRestClientConfig,
 		logger: Arc<Logger>, node_metrics: Arc<RwLock<NodeMetrics>>,
-	) -> (Self, Option<BestBlock>) {
+	) -> (Self, Option<BlockLocator>) {
 		let bitcoind_chain_source = BitcoindChainSource::new_rest(
 			rpc_host,
 			rpc_port,

src/lib.rs

@@ -117,6 +117,7 @@ pub use balance::{BalanceDetails, LightningBalance, PendingSweepBalance};
 pub use bip39;
 pub use bitcoin;
 use bitcoin::secp256k1::PublicKey;
+use bitcoin::BlockHash;
 #[cfg(feature = "uniffi")]
 pub use bitcoin::FeeRate;
 #[cfg(not(feature = "uniffi"))]
@@ -145,7 +146,7 @@ use gossip::GossipSource;
 use graph::NetworkGraph;
 use io::utils::update_and_persist_node_metrics;
 pub use lightning;
-use lightning::chain::BestBlock;
+use lightning::chain::BestBlock as BlockLocator;
 use lightning::impl_writeable_tlv_based;
 use lightning::ln::chan_utils::FUNDING_TRANSACTION_WITNESS_WEIGHT;
 use lightning::ln::channel_state::ChannelDetails as LdkChannelDetails;
@@ -2056,6 +2057,22 @@ impl Drop for Node {
 	}
 }
 
+/// The best known block as identified by its hash and height.
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
+#[cfg_attr(feature = "uniffi", derive(uniffi::Record))]
+pub struct BestBlock {
+	/// The block's hash.
+	pub block_hash: BlockHash,
+	/// The height at which the block was confirmed.
+	pub height: u32,
+}
+
+impl From<BlockLocator> for BestBlock {
+	fn from(locator: BlockLocator) -> Self {
+		Self { block_hash: locator.block_hash, height: locator.height }
+	}
+}
+
 /// Represents the status of the [`Node`].
 #[derive(Clone, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "uniffi", derive(uniffi::Record))]

src/wallet/mod.rs

@@ -35,7 +35,7 @@ use lightning::chain::chaininterface::{
 	BroadcasterInterface, INCREMENTAL_RELAY_FEE_SAT_PER_1000_WEIGHT,
 };
 use lightning::chain::channelmonitor::ANTI_REORG_DELAY;
-use lightning::chain::{BestBlock, ClaimId, Listen};
+use lightning::chain::{BestBlock as BlockLocator, ClaimId, Listen};
 use lightning::ln::channelmanager::PaymentId;
 use lightning::ln::funding::FundingTxInput;
 use lightning::ln::inbound_payment::ExpandedKey;
@@ -136,7 +136,7 @@ impl Wallet {
 			.collect()
 	}
 
-	pub(crate) fn current_best_block(&self) -> BestBlock {
+	pub(crate) fn current_best_block(&self) -> BlockLocator {
 		let checkpoint = self.inner.lock().expect("lock").latest_checkpoint();
 		let mut current_block = Some(checkpoint.clone());
 		let previous_blocks = std::array::from_fn(|_| {
@@ -145,7 +145,7 @@ impl Wallet {
 			current_block = Some(parent.clone());
 			Some(parent.hash())
 		});
-		BestBlock { block_hash: checkpoint.hash(), height: checkpoint.height(), previous_blocks }
+		BlockLocator { block_hash: checkpoint.hash(), height: checkpoint.height(), previous_blocks }
 	}
 
 	pub(crate) fn apply_update(&self, update: impl Into<Update>) -> Result<(), Error> {
@@ -1498,7 +1498,7 @@ impl Listen for Wallet {
 		};
 	}
 
-	fn blocks_disconnected(&self, _fork_point_block: BestBlock) {
+	fn blocks_disconnected(&self, _fork_point_block: BlockLocator) {
 		// This is a no-op as we don't have to tell BDK about disconnections. According to the BDK
 		// team, it's sufficient in case of a reorg to always connect blocks starting from the last
 		// point of disagreement.