Allow users to the rustls crypto provider used by electrum-client

Recently `rustls` introduced a new default crypto provider, `aws-lc-rc`.
While it generally works fine, it doesn't seem to build properly on
`aarch64-apple-ios`. Here, we therefore allow the users to decide which
crypto provider the `electrum-client` client should use for its `rustls`
TLS backend. To this end, we disable default features while keeping the
`proxy` enabled, as it's a prerequisite for the
`electrum_client::Client` to be exposed / usable (also see
bitcoindevkit/rust-electrum-client#91).

Author: tnull

lightning-transaction-sync/Cargo.toml

@@ -19,16 +19,24 @@ time = []
 esplora-async = ["async-interface", "esplora-client/async", "esplora-client/tokio", "futures"]
 esplora-async-https = ["esplora-async", "esplora-client/async-https-rustls"]
 esplora-blocking = ["esplora-client/blocking"]
-electrum = ["electrum-client"]
 async-interface = []
 
+# dummy feature to enable the common codepaths for electrum
+_electrum = []
+# the 'default' electrum feature, enabling `rustls` with the `aws-lc-rs` crypto provider
+electrum = ["_electrum", "electrum-client/use-rustls"]
+electrum-rustls = ["electrum"]
+
+# this feature enables `rustls` with the `ring` crypto provider
+electrum-rustls-ring = ["_electrum", "electrum-client/use-rustls-ring"]
+
 [dependencies]
 lightning = { version = "0.2.0", path = "../lightning", default-features = false, features = ["std"] }
 lightning-macros = { version = "0.2", path = "../lightning-macros", default-features = false }
 bitcoin = { version = "0.32.2", default-features = false }
 futures = { version = "0.3", optional = true }
 esplora-client = { version = "0.11", default-features = false, optional = true }
-electrum-client = { version = "0.22.0", optional = true }
+electrum-client = { version = "0.22.0", optional = true, default-features = false, features = ["proxy"] }
 
 [dev-dependencies]
 lightning = { version = "0.2.0", path = "../lightning", default-features = false, features = ["std", "_test_utils"] }

lightning-transaction-sync/src/error.rs

@@ -65,14 +65,14 @@ impl From<esplora_client::Error> for InternalError {
 	}
 }
 
-#[cfg(feature = "electrum")]
+#[cfg(feature = "_electrum")]
 impl From<electrum_client::Error> for InternalError {
 	fn from(_e: electrum_client::Error) -> Self {
 		Self::Failed
 	}
 }
 
-#[cfg(feature = "electrum")]
+#[cfg(feature = "_electrum")]
 impl From<electrum_client::Error> for TxSyncError {
 	fn from(_e: electrum_client::Error) -> Self {
 		Self::Failed

lightning-transaction-sync/src/lib.rs

@@ -74,17 +74,17 @@
 #[cfg(any(feature = "esplora-blocking", feature = "esplora-async"))]
 mod esplora;
 
-#[cfg(any(feature = "electrum"))]
+#[cfg(any(feature = "_electrum"))]
 mod electrum;
 
-#[cfg(any(feature = "esplora-blocking", feature = "esplora-async", feature = "electrum"))]
+#[cfg(any(feature = "esplora-blocking", feature = "esplora-async", feature = "_electrum"))]
 mod common;
-#[cfg(any(feature = "esplora-blocking", feature = "esplora-async", feature = "electrum"))]
+#[cfg(any(feature = "esplora-blocking", feature = "esplora-async", feature = "_electrum"))]
 mod error;
-#[cfg(any(feature = "esplora-blocking", feature = "esplora-async", feature = "electrum"))]
+#[cfg(any(feature = "esplora-blocking", feature = "esplora-async", feature = "_electrum"))]
 pub use error::TxSyncError;
 
-#[cfg(feature = "electrum")]
+#[cfg(feature = "_electrum")]
 pub use electrum::ElectrumSyncClient;
 #[cfg(any(feature = "esplora-blocking", feature = "esplora-async"))]
 pub use esplora::EsploraSyncClient;

lightning-transaction-sync/tests/integration_tests.rs

@@ -1,12 +1,12 @@
 #![cfg(all(
 	not(target_os = "windows"),
-	any(feature = "esplora-blocking", feature = "esplora-async", feature = "electrum")
+	any(feature = "esplora-blocking", feature = "esplora-async", feature = "_electrum")
 ))]
 
 use lightning::chain::transaction::{OutPoint, TransactionData};
 use lightning::chain::{Confirm, Filter, WatchedOutput};
 use lightning::util::test_utils::TestLogger;
-#[cfg(feature = "electrum")]
+#[cfg(feature = "_electrum")]
 use lightning_transaction_sync::ElectrumSyncClient;
 #[cfg(any(feature = "esplora-blocking", feature = "esplora-async"))]
 use lightning_transaction_sync::EsploraSyncClient;
@@ -332,7 +332,7 @@ async fn test_esplora_syncs() {
 }
 
 #[test]
-#[cfg(feature = "electrum")]
+#[cfg(feature = "_electrum")]
 fn test_electrum_syncs() {
 	let (bitcoind, electrsd) = setup_bitcoind_and_electrsd();
 	generate_blocks_and_wait(&bitcoind, &electrsd, 101);