Make bdk_esplora wasm compatible again

There's a huge todo!() for the AsyncClient

crates/bdk/Cargo.toml

@@ -39,6 +39,12 @@ keys-bip39 = ["bip39"]
 hardware-signer = ["hwi"]
 test-hardware-signer = ["hardware-signer"]
 
+
+# This feature is used to run `cargo check` in our CI targeting wasm. It's not recommended
+# for libraries to explicitly include the "getrandom/js" feature, so we only do it when
+# necessary for running our CI. See: https://docs.rs/getrandom/0.2.8/getrandom/#webassembly-support
+dev-getrandom-wasm = ["getrandom/js"]
+
 [dev-dependencies]
 lazy_static = "1.4"
 env_logger = "0.7"

crates/esplora/Cargo.toml

@@ -13,4 +13,9 @@ readme = "README.md"
 
 [dependencies]
 bdk_chain = { path = "../chain", version = "0.3.1", features = ["serde", "miniscript"] }
-esplora-client = { version = "0.3" }
+esplora-client = { version = "0.3", default-features = false }
+
+[features]
+default = ["async", "blocking"]
+async = ["esplora-client/async"]
+blocking = ["esplora-client/blocking"]

crates/esplora/src/lib.rs

@@ -77,6 +77,7 @@ pub trait EsploraExt {
     }
 }
 
+#[cfg(feature = "blocking")]
 impl EsploraExt for esplora_client::BlockingClient {
     fn scan<K: Ord + Clone>(
         &self,
@@ -302,3 +303,18 @@ fn map_confirmation_time(tx_status: &TxStatus, height_at_start: u32) -> Confirma
         _ => ConfirmationTime::Unconfirmed,
     }
 }
+
+#[cfg(feature = "async")]
+impl EsploraExt for esplora_client::AsyncClient {
+    fn scan<K: Ord + Clone>(
+        &self,
+        _local_chain: &BTreeMap<u32, BlockHash>,
+        _keychain_spks: BTreeMap<K, impl IntoIterator<Item = (u32, Script)>>,
+        _txids: impl IntoIterator<Item = Txid>,
+        _outpoints: impl IntoIterator<Item = OutPoint>,
+        _stop_gap: usize,
+        _parallel_requests: usize,
+    ) -> Result<KeychainScan<K, ConfirmationTime>, Error> {
+        todo!()
+    }
+}